US20070102001A1 - Disposable laryngeal mask airway device - Google Patents

Abstract

The disclosed laryngeal mask airway device includes a mask portion and an airway tube. The mask portion includes an inflatable cuff, which defines a central opening when the cuff is inflated. The airway tube defines an internal passage extending from a proximal end of the tube to a distal end of the tube. The airway tube further defines two or more tabs disposed near the distal end of the tube. The mask portion is coupled to the airway tube near the distal end of the airway tube, and the tabs extend from the airway tube into the central opening defined by the cuff when the cuff is inflated.

Description

REFERENCE TO RELATED APPLICATIONS
• This application is a divisional of and claims priority under 35 U.S.C., §120 to U.S. patent application Ser. No. 10/138,806, filed May 3, 2002, the entire contents of which are incorporated herein by reference, and which claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 60/314,438, entitled “Disposable LMA,” which was filed Aug. 23, 2001, which is expressly incorporated herein by reference in its entirety.
• This application is related to U.S. patent application Ser. No. 09/544,681 entitled “Disposable LMA”, filed on Apr. 7, 2000 (Attorney Docket No. LMA-003, 108195-120), now U.S. Pat. No. 6,705,318, issued on Mar. 16, 2004.
BACKGROUND OF THE INVENTION
• The present invention relates to a laryngeal mask airway device. More specifically, the present invention relates to reduced cost laryngeal masks, improved geometric configurations for laryngeal masks, and to methods of inexpensively fabricating such masks.
• The laryngeal mask airway device is a well-known device that is useful for establishing airways in unconscious patients. Such devices have been in use for about twelve years and offer an alternative to the older, even better known, endotracheal tube. For at least seventy years, endotracheal tubes comprising a long slender tube with an inflatable balloon disposed at the tube's distal end have been used for establishing airways in unconscious patients. In operation, the endotracheal tube's distal end is inserted through the mouth of the patient, past the patient's laryngeal inlet (or glottic opening), and into the patient's trachea. Once so positioned, the balloon is inflated so as to form a seal with the interior lining of the trachea. After this seal is established, positive pressure may be applied to the tube's proximal end to ventilate the patient's lungs. Also, the seal between the balloon and the inner lining of the trachea protects the lungs from aspiration (e.g., the seal prevents material regurgitated from the stomach from being aspirated into the patient's lungs).
• Although they have been enormously successful, endotracheal tubes suffer from several major disadvantages. The principal disadvantage of the endotracheal tube relates to the difficulty of properly inserting the tube. Inserting an endotracheal tube into a patient is a procedure that requires a high degree of skill. Also, even for skilled practitioners, insertion of an endotracheal tube is sometimes difficult or not possible. In many instances, the difficulty of inserting endotracheal tubes has tragically led to the death of a patient because it was not possible to establish an airway in the patient with sufficient rapidity.
• In addition to this principal disadvantage, there are also other disadvantages associated with endotracheal tubes. For example, intubation with an endotracheal tube often causes patients to suffer from severe “sore throats.” The “sore throat” is principally caused by friction between the tube and the notch between the patient's arytenoid cartilages. Another disadvantage is that patients can not cough effectively while intubated with an endotracheal tube. Yet another problem with endotracheal tubes relates to the manner in which they are inserted. Inserting an endotracheal tube normally requires manipulations of the patient's head and neck and further requires the patient's jaw to be forcibly opened widely. These necessary manipulations make it difficult, or undesirable, to insert an endotracheal tube into a patient who may be suffering from a neck injury. Still another disadvantage is that endotracheal tubes provide an airway that is relatively small or narrow. The size of the airway must be relatively narrow because the distal end of the tube must be sufficiently small to fit into the trachea.
• In contrast to the endotracheal tube, it is relatively easy to insert a laryngeal mask airway device into a patient and thereby establish an airway. Also, the laryngeal mask airway device is a “forgiving” device in that even if it is inserted improperly, it still tends to establish an airway. Accordingly, the laryngeal mask airway device is often thought of as a “life saving” device. Also, the laryngeal mask airway device may be inserted with only relatively minor manipulations of the patient's head, neck, and jaw. Further, the laryngeal mask airway device provides for ventilation of the patient's lungs without requiring contact with the sensitive inner lining of the trachea and the size of the airway established is typically significantly larger than the size of the airway established with an endotracheal tube. Also, the laryngeal mask airway device does not interfere with coughing to the same extent as endotracheal tubes. Largely due to these advantages, the laryngeal mask airway device has enjoyed increasing popularity over the last twelve years.
• FIG. 1 shows a perspective view of a prior art laryngealmask airway device100 andFIG. 2 illustrates adevice100 that has been inserted into a patient. Laryngeal mask airway devices such asdevice100 are described for example in U.S. Pat. No. 4,509,514.Device100 includes a flexiblecylindrical tube110 and amask portion130.Tube110 extends from aproximal end112 to adistal end114 andmask portion130 is coupled to the tube'sdistal end114.Mask portion130 includes aproximal end132 and a generally ellipticalinflatable cuff134.Mask portion130 also defines a central passageway extending fromproximal end132 to anopen end136 ofcuff134. Thedistal end114 oftube110 is telescopically fit into theproximal end132 ofmask portion130, anddevice100 provides a continuous, sealed, airway extending fromproximal end112 oftube110 to theopen end136 ofcuff134.Device100 also includes aninflation tube138 for selectively inflating or deflatingcuff134.
• In operation, thecuff134 is deflated, and then the mask portion is inserted through the patient's mouth into the patient's pharynx. The mask portion is preferably positioned so that adistal end140 ofcuff134 rests against the patient's normally closed esophagus and so that theopen end136 of thecuff134 is aligned with the entryway of the patient's trachea (i.e., the patient's glottic opening). After the mask portion is so positioned, the cuff is inflated thereby forming a seal around the patient's glottic opening and this establishes a sealed airway extending from theproximal end112 of thetube110 to the patient's trachea.
• For convenience of exposition, the term “fully inserted configuration” shall be used herein to refer to a laryngeal mask airway device that has been inserted into a patient and has the following characteristics: (1) the mask portion is disposed around the patient's glottic opening; (2) the cuff is inflated forming a seal around the patient's glottic opening; and (3) the airway tube extends from a proximal end located outside the patient's mouth to a distal end that is coupled to the mask portion, the tube extending through the patient's mouth and the patient's natural upper airway so that the device provides a sealed airway extending from the tube's proximal end to the patient's lungs.FIG. 2 shows a laryngeal mask airway device in the fully inserted configuration.
• Whendevice100 is in the fully inserted configuration,device100 advantageously does not contact the interior lining of the trachea. Rather, the seal is established by contact between the tissues surrounding the patient's laryngeal inlet and theinflatable cuff134. Unlike the delicate interior lining of the trachea, the tissues at the laryngeal inlet are accustomed to contact with foreign matter. For example, during the act of swallowing food, the food is normally squeezed against these tissues on its way to the esophagus. These tissues are accordingly less sensitive and less susceptible to being damaged by contact with the inflatable cuff.
• FIG. 3 shows a sectional side view of themask portion230 of another prior art laryngeal mask airway device. The illustratedmask portion230, which is described more fully in U.S. Pat. No. 5,355,879, includes aninflatable cuff234 and abackplate250.Backplate250 defines aproximal end232 for receiving, or coupling to, a cylindrical airway tube (not shown).Mask portion230 defines a sealed passageway, or airway, that extends fromproximal end232 through to theopen end236 ofcuff234. Thismask portion230 also includes an inflatable back cushion that, when inflated, expands to the contour illustrated byphantom outline252. As shown inFIG. 3, the cross sections of prior art cuffs are generally circular. The thickness T1 of the material used to form the cuff (i.e., the thickness of the cuff wall) is normally about 0.7-0.8 millimeters.
• U.S. Pat. No. 5,303,697 describes an example of another type of prior art device that may be referred to as an “intubating laryngeal mask airway device.” The intubating device is useful for facilitating insertion of an endotracheal tube. After an intubating laryngeal mask airway device has been located in the fully inserted configuration, the device can act as a guide for a subsequently inserted endotracheal tube. Use of the laryngeal mask airway device in this fashion facilitates what is commonly known as “blind insertion” of the endotracheal tube. Only minor movements of the patient's head, neck, and jaw are required to insert the intubating laryngeal mask airway device, and once the device has been located in the fully inserted configuration, the endotracheal tube may be inserted with virtually no additional movements of the patient. This stands in contrast to the relatively large motions of the patient's head, neck, and jaw that would be required if the endotracheal tube were inserted without the assistance of the intubating laryngeal mask airway device.
• U.S. Pat. No. 5,632,271 describes an example of yet another type of prior art laryngeal mask airway device. In addition to providing an airway tube for ventilating a patient's lungs, this device also provides a second tube, a drainage tube, used for draining or removing regurgitated material. The distal end of the drainage tube is disposed proximal to the normally closed entrance to the patient's esophagus. In addition to providing drainage, the drainage tube may also be used to guide insertion of a gastric tube.
• In general, prior art laryngeal mask airway devices have been manufactured by molding elastomeric materials such as silicone to desired shapes. One advantage of these materials is that they are durable enough to permit the devices to be sterilized in an autoclave and reused. For example, laryngeal mask airway devices sold by LMA International SA of Henley, England are guaranteed to survive forty sterilizations, and in practice these devices may generally be sterilized (and reused) more than forty times before becoming too worn for reuse. However, one disadvantage of these materials is that they are relatively expensive. Accordingly, it would be advantageous to develop a reduced cost laryngeal mask airway device.
• Several attempts have been made in the prior art to provide reduced cost laryngeal mask airway devices. For example, U.S. Pat. No. 6,012,452 discloses a laryngeal mask airway device in which the mask portion is formed by adhering a foam material to both sides of a backplate. The foam forms an inflatable cuff that is attached to both sides of the plate. U.S. Pat. No. 5,983,897 discloses another laryngeal mask airway device in which the mask portion is formed by attaching cuff members to the top and bottom of a backplate. The cuff members may be formed from flexible, resilient plastics material, such as PVC. One disadvantage of the devices disclosed in the '897 and '452 patents is that the assembly of the disclosed mask portions necessarily involves two steps: a first step of fabricating the backplate and then a second step of adhering the cuff to the top and bottom of the plate. It would therefore be advantageous to develop a process for simultaneously forming all parts of the mask portion of a laryngeal mask airway device.
• In addition to cost, another disadvantage of prior art laryngeal mask airway devices relates to the quality of the seal established between the patient and the device. Thedevice100 shown inFIG. 1 generally maintains a seal up to about twenty cm H₂O. That is, when the device is in the fully inserted configuration, the seal between the device and the patient will be maintained as long as the pressure applied to the proximal end of the airway tube is less than approximately twenty cm H₂O. However, if greater pressures are applied to the proximal end of the airway tube, the seal tends to be lost thereby causing loss of some fraction of the delivered gas volume, so that positive pressure ventilation may be less effective. This stands in contrast to the endotracheal tube, which can normally maintain a seal up to fifty cm H₂O. Accordingly, it would be advantageous to provide a laryngeal mask airway device that provides improved seals.
• Still another disadvantage of prior art laryngeal mask airway devices relates to the profile, or geometric configuration, of the deflated device. When the cuff of a laryngeal mask airway device is deflated, the device would ideally, automatically, assume a shape that was optimized for facilitating insertion. However, prior art devices do not tend to automatically form such shapes when the cuff is deflated. Accordingly, several “forming tools” have been provided for affecting the shape of the deflated device. U.S. Pat. No. 5,711,293 discloses one such forming tool. However, it would be advantageous to provide a device that automatically assumes a profile that facilitated insertion when the cuff was deflated.
• Yet another disadvantage of prior art laryngeal mask airway devices relates to the manner in which they are inserted into a patient. Anesthesiologists or other practitioners insert many types of prior art laryngeal mask airway devices by pushing one of their fingers against the proximal end of the cuff. Unfortunately, this procedure requires the practitioner to insert their finger into the patient's mouth and guide the device past the patient's throat. Since many practitioners prefer to avoid inserting their fingers into patient's mouths, several insertion tools have been developed for facilitating insertion of various laryngeal mask airway devices. However, it would be advantageous to provide a laryngeal mask airway device that could be inserted without an insertion tool and without requiring insertion of a finger into the patient's mouth.
SUMMARY OF THE INVENTION
• These and other objects are provided by laryngeal mask airway devices that are characterized by improved geometric configurations and by methods of making such a devices. As will be discussed below, a reduced cost process for making a laryngeal mask airway device according to the invention includes a process known as rotational molding. The improved device includes two principal components: (1) a mask portion and (2) an airway tube. The device is fabricated by attaching the backplate portion of the airway tube to the mask portion. As will be discussed in greater detail below, the configuration of the two principal components (1) reduces the cost of fabricating the device and (2) improves the performance of the device.
• In another aspect, the invention provides methods and structures for resisting compressive forces that can be generated within a patient so as to maintain an open airway passage in a laryngeal mask airway device.
• Still other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description wherein several embodiments are shown and described, simply by way of illustration of the best mode of the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not in a restrictive or limiting sense, with the scope of the application being indicated in the claims.
BRIEF DESCRIPTION OF THE FIGURES
• For a fuller understanding of the nature and objects of the present invention, reference should be made to the following detailed description taken in connection with the accompanying drawings in which the same reference numerals are used to indicate the same or similar parts wherein:
• FIG. 1 shows a perspective view of a prior art laryngeal mask airway device.
• FIG. 2 shows a prior art laryngeal mask airway device inserted into a patient in the fully inserted configuration.
• FIG. 3 shows a sectional view of another prior art laryngeal mask airway device.
• FIG. 4A shows a side view of a laryngeal mask airway device constructed according to the invention, the mask portion of the device being in an inflated condition.
• FIGS. 4B and 4C show two perspective views of the device shown inFIG. 4A.
• FIG. 5A shows a side view of the inflated mask portion of the device shown inFIGS. 4A, 4B, and4C.
• FIGS. 5B and 5C show two perspective views of the anterior portion of the mask portion shown inFIG. 5A.
• FIG. 5D shows a perspective view of the posterior portion of the mask portion shown inFIG. 5A.
• FIG. 5E shows a posterior view of the mask portion shown inFIG. 5A.
• FIG. 6 shows a sectional view of the mask portion taken in the direction of line6-6 as shown inFIG. 5A.
• FIG. 7A shows a side view of the mask portion shown inFIG. 5A when the mask portion is deflated.
• FIG. 7B shows an anterior view of the deflated mask portion shown inFIG. 7A.
• FIG. 8A shows a top view of a mold that may be used to make the mask portion shown inFIG. 5-7.
• FIG. 8B shows a sectional view of the mold taken in the direction ofline8B-8B as shown inFIG. 8A.
• FIGS. 8C and 8D show perspective views of the mold shown inFIG. 8A.
• FIG. 9A shows a side view of the airway tube of the device shown inFIGS. 4A, 4B, and4C.
• FIG. 9B shows a perspective view of the proximal section of the airway tube shown inFIG. 9A.
• FIGS. 9C and 9D show views of the proximal section taken in the direction oflines9C-9C and9D-9D, respectively, as shown inFIG. 9B.
• FIG. 9E shows a side view of the integral tube and backplate section of the airway tube shown inFIG. 9A.
• FIGS. 9F and 9G show two perspective views of the integral tube and backplate section shown inFIG. 9E.
• FIG. 10A shows a sectional view of the proximal section inserted into the integral tube and backplate section taken in the direction of theline10A-10A as shown inFIG. 9A.
• FIG. 10B shows a sectional view of the curved portion of the integral tube and backplate section taken in the direction ofline10B-10B as shown inFIG. 9A.
• FIG. 10C shows a sectional view of the same component illustrated inFIG. 10B when that component is subjected to external compressive forces.
• FIG. 10D shows a side view of an embodiment of an intubating laryngeal mask airway device constructed according to the invention, and an endotracheal tube extending through the device.
• FIG. 10E shows a sectional view of the intubating laryngeal mask airway device taken alongline10E-10E as shown inFIG. 10D.
• FIG. 10F shows a side view of another embodiment of a laryngeal mask airway device constructed according to the invention.
• FIG. 10G shows a perspective view of the embodiment shown inFIG. 10F.
• FIG. 11 shows a perspective view of a tube that has formed a kink in response to bending of the tube.
• FIG. 12 shows a perspective view of a laryngeal mask airway device constructed according to the invention in which the inflation tube has been attached to the airway tube so that the inflation tube extends into one of the grooves in the airway tube.
• FIG. 13 illustrates how the airway tube shown inFIG. 9A deviates from its preformed configuration when the device is located in the fully inserted configuration.
• FIG. 14 shows a perspective view of the laryngeal side of the mask portion of a laryngeal mask airway device and illustrates the regions of the mask portion that form seals with different portions of the human anatomy when the device is located in the fully inserted configuration.
• FIG. 15A shows a sectional view of a prior art laryngeal mask airway device that has been located in the fully inserted configuration.
• FIG. 15B shows a sectional view of a laryngeal mask airway device constructed according to the invention that has been located in the fully inserted configuration.
• FIG. 16A shows a side view of the device shown inFIG. 4A when the mask portion is deflated.
• FIGS. 16B and 16C show perspective views of the device, with deflated mask portion, shown inFIG. 16A.
• FIG. 17 shows a laryngeal mask airway device constructed according to the invention that is partially inserted into a patient.
• FIG. 18A shows a side view of another laryngeal mask airway device constructed according to the invention.
• FIGS. 18B and 18C show perspective views of the device shown inFIG. 18A.
• FIG. 18D shows a sectional view of the airway tube taken in the direction of theline18D-18D as shown inFIG. 18A.
• FIG. 19A illustrates how the airway tube of the device shown inFIGS. 18A-18D can be used to guide a subsequently inserted endotracheal tube.
• FIG. 19B shows an alternative embodiment of the device shown inFIGS. 18A-18C constructed according to the invention in which the proximal end of the plate is not fixed to the proximal end of the backplate portion of the airway tube.
• FIG. 20 shows an alternative embodiment of a mask portion constructed according to the invention.
• FIG. 21 is a simplified view in perspective for another laryngeal mask airway device device according to the invention, as seen in three-quarter perspective and viewing the posterior side of mask structure, in inflated condition at the distal end of an airway tube.
• FIG. 22 is a similar view of the structure ofFIG. 21, as seen from the anterior (or trachea-facing) side of the device ofFIG. 21, but in the evacuated state wherein thin-film material of the inflation is collapsed and matted against skeletal base structure of the device.
• FIG. 23 is a view similar toFIG. 21, for a laryngeal mask airway device having a gastric-drainage feature of the invention.
• FIG. 24 is a view similar toFIG. 22, for the device ofFIG. 23.
• FIG. 25 is a sectional view taken generally in the longitudinal sagittal plane of the device ofFIG. 23, certain parts being omitted, for clarity.
• FIG. 26 is a plan view of the posterior side of the device ofFIG. 23, certain parts being omitted for clarity.
• FIG. 27 is a plan view as inFIG. 26 but with added showing, to include structure omitted fromFIG. 26.
• FIG. 28 is a sectional view, taken at28-28 inFIG. 27.
• FIG. 29 is a similar sectional view, but taken at29-29 inFIG. 27.
• FIG. 30 is a longitudinal section as inFIG. 25, for a modified embodiment of the invention.
• FIG. 31 is another and similar longitudinal section, taken only to show an integrally formed feature of the invention, being a major component of the embodiment ofFIG. 30.
• FIG. 31A is a view similar toFIG. 31 to show a modification.
• FIG. 32 is a plan view of the posterior side of the component ofFIG. 31.
• FIG. 33 is a view of a slightly modified version of the component ofFIG. 31.
• FIG. 34A shows a side view of another laryngeal mask airway device constructed according to the invention.
• FIGS. 34B and 35C show perspective views of the device shown inFIG. 34A.
• FIG. 34D shows a side view of the device shown inFIG. 34A during construction of the device.
• FIG. 35A shows a side view of the mask portion, when inflated, of the device shown inFIG. 34A.
• FIG. 35B shows a view of the anterior side of the mask portion shown inFIG. 35A taken in the direction of theline35B-35B as shown inFIG. 35A.
• FIG. 35C shows a perspective view of the anterior surface of the mask portion shown inFIG. 35A.
• FIG. 35D shows a view of the posterior side of the mask portion shown inFIG. 35A taken in the direction ofline35D-35D as shown inFIG. 35A.
• FIG. 35E shows a sectional view of the mask portion shown inFIG. 35A taken in the direction of theline35E-35E as shown inFIG. 35A.
• FIG. 36 shows a sectional view of a mold that may be used to form the mask portion shown inFIGS. 35A-35E.
• FIG. 37A shows a side view of the integral tube and backplate section of the airway tube of the device shown inFIGS. 34A-34C.
• FIG. 37B shows a view of the inner side of the integral tube and backplate section shown inFIG. 37A.
• FIG. 37C shows a view of the proximal end of the integral tube and backplate section shown inFIG. 37A taken in the direction of theline37C-37C as shown inFIG. 37A.
• FIG. 37D shows a sectional view of the integral tube and backplate section shown inFIG. 37A taken along theline37D-37D shown inFIG. 37A.
• FIG. 38A shows a perspective view of the connector section of the airway tube of the laryngeal mask airway device shown inFIGS. 34A-34C.
• FIGS. 38B, 38C, and38D show views of the connector section shown inFIG. 38A taken in the direction oflines38B-38B,38C-38C, and38D-38D, respectively, as shown inFIG. 38A.
• FIG. 39A shows a perspective view of an endotracheal tube being inserted through the device shown inFIGS. 34A-34C.
• FIG. 39B shows an anterior view of the device shown inFIG. 39A as the endotracheal tube extends through the central aperture defined in the support of the mask portion.
• FIG. 40A shows an anterior view of another embodiment of a mask portion constructed according to the invention in which the support defines a fenestration for facilitating insertion of an endotracheal tube.
• FIG. 40B shows a side view of an endotracheal tube being inserted through the mask portion shown inFIG. 40A.
• FIG. 41A shows a top view of another support designed according to the invention.
• FIG. 41B shows a side view of the support shown inFIG. 41A taken in the direction of theline41B-41B as shown inFIG. 41A.
• FIGS. 42 and 43 show top views of other supports constructed according to the invention.
• FIG. 44 shows an anterior view of a mask portion of the type shown inFIGS. 35A-35E being squeezed between two fingers to illustrate the response of the mask portion to pressure exerted when the mask portion is disposed within a patient.
• FIG. 45A shows a sectional view of another mask portion constructed according to the invention.
• FIG. 45B shows an exploded view of the support shown inFIG. 44A.
• FIG. 45C shows a posterior aspect of the mask portion shown inFIG. 45A.
• FIG. 46 shows an anterior view of a mask portion of the type shown inFIGS. 45A-45C being squeezed between two fingers to illustrate the response of the mask portion to pressure exerted when the mask portion is disposed within a patient.
• FIG. 47A shows a side view of another embodiment of the integral tube and backplate section of the airway tube of a laryngeal mask airway device constructed according to the invention.
• FIG. 47B shows a view of the inner side of the integral tube and backplate section shown inFIG. 47A.
• FIG. 47C shows a view of the bar taken in the direction ofline47C-47C as shown inFIG. 47A.
• FIG. 47D shows an endotracheal tube being inserted through a laryngeal mask airway device constructed according to the invention so as to include a bar of the type shown inFIGS. 47A-47C.
• FIG. 48A shows a perspective view of yet another embodiment of the integral tube and backplate section of an airway tube constructed according to the invention.
• FIG. 48B shows a side view of the integral tube and backplate section shown inFIG. 48A.
• FIG. 48C shows a view of the anterior side of a laryngeal mask airway device constructed according to the invention using the airway tube shown inFIGS. 48A and 48B.
• FIG. 48D shows a side view of the device shown inFIG. 48C.
• FIG. 49A shows an anterior perspective view of another laryngeal mask airway device constructed according to the invention.
• FIG. 49B shows a side view of the device shown inFIG. 49A.
• FIGS. 49C and 49D show side and anterior views, respectively, of the cuff shown inFIGS. 49A and 49B.
• FIG. 49E shows a sectional view of the cuff shown inFIG. 49C taken in the direction ofarrow49E-49E.
• FIG. 49F shows a sectional view of the device shown inFIG. 49B taken in the direction ofarrow49F-49F.
• FIG. 49G shows a sectional view of a laryngeal mask airway device in which the backplate is attached at a equatorial location of the cuff.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
• FIG. 4A shows a side view of one embodiment of a laryngealmask airway device400 constructed according to one aspect of the invention.FIGS. 4B and 4C show two perspective views ofdevice400.Device400 is preferably constructed from two separate pieces that are bonded, or adhered, together. The first piece is anairway tube410 and the second piece is amask portion430. InFIGS. 4A, 4B, and4C, themask portion430 is shown in an inflated condition. As will be discussed in greater detail below,mask portion430 may advantageously be formed by a process called rotational molding. Theairway tube410 may also be produced by rotational molding, or alternatively, could be produced using injection or other types of molding.
• FIG. 5A shows a side view ofmask portion430 when inflated.FIGS. 5B and 5C show two perspective views of the anterior side ofmask portion430 when inflated.FIG. 5D shows a perspective view of the posterior side ofmask portion430 when inflated, andFIG. 5E shows a view of the posterior side ofmask portion430 when inflated. The terms anterior and posterior as used above in connection withFIGS. 5B-5E are made with reference to the fully inserted configuration. That is, when thedevice400 is in the fully inserted configuration, the portion of themask portion430 shown inFIGS. 5B and 5C will be located forward of, or anterior to, the portion shown inFIGS. 5D and 5E. Also, whendevice400 is in the fully inserted configuration, the portion ofmask portion430 shown inFIGS. 5D and 5E will be disposed proximal to the patient's pharyngeal wall, posterior to the portions shown inFIGS. 5B and 5C.FIG. 6 shows a sectional view ofmask portion430 taken in the direction of line6-6 as shown inFIG. 5A.FIGS. 7A and 7B show side and anterior views, respectively, ofmask portion430 when deflated.
• Mask portion430 includes aplate440, aninflatable cuff460, and aninflation tube490.Mask portion430 also defines aproximal end432 and a distal end434 (shown for example inFIG. 5D).Plate440 is characterized by a generally elliptical shape and defines a central aperture or through hole442 (shown best inFIG. 5E). For convenience of exposition, the shape ofplate440 may be referred to as that of an elliptical annulus. A classic annulus has circular symmetry, however, the elliptical annulus ofplate442 follows the elliptical profile illustrated inFIG. 5E.Plate440 also defines apharyngeal side444 and a laryngeal side446 (shown for example inFIG. 5A). Thepharyngeal side444 ofplate440 is so named because, as will be discussed below, thepharyngeal side444 is disposed proximal to the pharyngeal wall of a patient whendevice400 is in the fully inserted configuration. Thecentral aperture442 ofplate440 extends through the entire plate from thepharyngeal side444 to thelaryngeal side446. The distance between thepharyngeal side444 and thelaryngeal side446 ofplate440, or the thickness of the plate, shall be referred to as T2, as shown inFIG. 6. In some embodiments, the plate is substantially flat in that the thickness T2 is substantially uniform throughout the plate. One preferred value for the thickness T2 of the substantiallyflat plate440 is about two millimeters plus or minus one millimeter. Even more preferably, the thickness T2 of the substantiallyflat plate440 is two millimeters plus or minus 0.5 millimeters. Even more preferably, the thickness T2 of the substantiallyflat plate440 is substantially equal to two millimeters. In other embodiments, it may be advantageous for the plate to have a tapering thickness so that the plate is thicker at the proximal end than at the distal end. For example, the thickness of the plate T2 may be about two millimeters at the proximal end and may smoothly taper to about one and a half millimeters at the distal end.
• Inflatable cuff460 is formed from a very thin, flexible, sheet of material that is attached to thelaryngeal side446 ofplate440. As shown best inFIG. 6, the cross-section ofcuff460, when inflated, is generally U-shaped (or has the shape of an inverted “U”). The generally elliptical inner periphery460-I ofcuff460 is sealed, or attached, to plate440 proximal to the generally elliptical periphery ofaperture442, and the generally elliptical outer periphery460-O ofcuff460 is sealed, or attached, to plate440 proximal to the generally elliptical outer periphery of theplate440. The thickness of the cuff (i.e., the cuff wall), as shown inFIG. 6, shall be referred to as T3. One preferred value for the thickness T3 of the cuff is about 0.04 to 0.24 millimeters. More preferably, the thickness T3 is in the range 0.08 to 0.20 millimeters (or 0.14 plus or minus 0.06 millimeters). Even more preferably, the thickness T3 of the cuff is 0.14 plus or minus 0.03 millimeters.
• For convenience of exposition, the shape of theinflated cuff460 shall be referred to as “generally toroidal”. The shape of the cuff is not strictly a torus for several reasons. For example, the cross section of the cuff is U-shaped rather than circular (as shown inFIG. 6). Also, a classic torus has a ring-like, or doughnut, shape (and is formed by rotating a circle about an axis in the plane of the circle that does not intersect the circle), whereas thecuff460 follows the generally elliptical shape of theplate440. Also, the thickness of the inflated cuff is not constant from the proximal end to the distal end (as shown for example inFIG. 5A by the angle alpha). However, despite these variations from the classic torus, the inflated cuff may be described as having a generally toroidal configuration (since it is essentially formed by sweeping the U-shaped cross section of the inflated cuff along the elliptical contour defined by the plate440).
• Plate440 andcuff460 ofmask portion430 cooperate to define a generally toroidal interior volume.Inflation tube490 extends from thepharyngeal side444 ofplate440 through the plate and into the interior volume to permit selective inflation and deflation ofcuff460.
• Likeplate440,mask portion430 defines a pharyngeal side and a laryngeal side. The pharyngeal side ofmask portion430 is coincident with thepharyngeal side444 ofplate440. Thelaryngeal side448 ofmask portion430 is defined byinflatable cuff460. As shown best inFIGS. 5A and 6, when thecuff460 is inflated, thelaryngeal side448 ofmask portion430 is defined by the exterior surface ofcuff460 at the portion of thecuff460 that is disposed opposite toplate440, or furthest fromplate440. Whendevice400 is in the fully inserted configuration, thelaryngeal side448 ofmask portion430 is in physical contact with the tissues surrounding the patient's laryngeal inlet. As shown best inFIGS. 5D and 5E, whencuff460 is inflated, theaperture442 extends entirely through the mask portion so that themask portion430 defines apassage442 that extends from the laryngeal side to the pharyngeal side.
• For convenience of exposition, three directions shall be defined with respect tomask portion430. The arrow PtD shown inFIG. 5A extends in a proximal-to-distal direction.Mask portion430 extends in the proximal-to-distal direction from theproximal end432 to thedistal end434. It will be appreciated that a distal-to-proximal direction extends opposite to, or is rotated 180 degrees from, the proximal-to-distal direction. The arrow LtP shown inFIG. 5A extends in a laryngeal-to-pharyngeal direction.Mask portion430 extends in the laryngeal-to-pharyngeal direction fromlaryngeal side448 topharyngeal side444. It will be appreciated that a pharyngeal-to-laryngeal direction extends opposite to, or is rotated 180 degrees from, the laryngeal-to-pharyngeal direction. (The laryngeal-to-pharyngeal direction could also be referred to as the “antero-posterior” direction.) The arrow LtR shown inFIG. 5E extends in the left-to-right direction. It will be appreciated that a right-to-left direction extends opposite to, or is rotated 180 degrees from, the left-to-right direction. These directions are so named because when thedevice400 is inserted into a patient, the device will extend from a left side to a right side within the patient. These right-to-left and left-to-right directions could also be referred to as “lateral” directions. The proximal-to-distal, laryngeal-to-pharyngeal, and left-to-right directions are mutually orthogonal and provide a convenient reference coordinate system for describing the device.
• As shown inFIG. 5A, the thickness of the inflated mask portion at the distal end434 (i.e., the distance between thepharyngeal side444 and thelaryngeal side448 ofmask portion430 as measured in the laryngeal-to-pharyngeal direction) shall be referred to as T4, and the thickness of the inflated mask portion at theproximal end432, as measured in the laryngeal-to-pharyngeal direction, shall be referred to as T5. Preferred values for T4 and T5 in female adult sizes are about 12.7 and 25.4 millimeters, respectively. (It will be appreciated that external dimensions such as T4 and T5 would be about thirteen percent larger in an adult male size of the laryngeal mask airway device. Unless otherwise stated, dimensions discussed herein will be for the female adult size.) The profile ofcuff460 is preferably smoothly tapered as shown inFIG. 5A so that the thickness of themask portion430 smoothly decreases from theproximal end432 to thedistal end434. This tapering can be described in terms of the angle alpha between thepharyngeal side444 and thelaryngeal side448 ofmask portion430, as shown inFIG. 5A. One preferred value for the angle alpha is about ten degrees plus or minus one degree. More preferably, the angle alpha is ten degrees plus or minus half a degree. Most preferably, the angle alpha is substantially equal to ten degrees. As will be discussed below, this angle alpha is selected to match the human anatomy to allow all portions of the inflated cuff to contact the tissues surrounding the laryngeal inlet and to thereby provide improved seals.
• Theplate440 shown inFIG. 5A is characterized by a substantially constant thickness. That is, the thickness T2 (as shown inFIG. 6) ofplate440 is substantially constant from the proximal end of the mask portion to the distal end of the mask portion and the variation in the mask portion's thickness is entirely provided by thecuff460. However, as mentioned above, in some embodiments, it may be advantageous to provideplate440 with a tapering thickness so that the distal end of the plate is thinner than the proximal end.
• As shown inFIG. 5E, the length of theplate440, or the distance between theproximal end432 and thedistal end434 as measured in the proximal-to-distal direction, shall be referred to as L1, and the length ofaperture442 as measured in the proximal-to-distal direction shall be referred to as L2. The width of theplate440, as measured in the left-to-right direction, shall be referred to as W1, and the width of theaperture442 as measured in the left-to-right direction shall be referred to as W2. In adult sizes ofdevice400, preferred values for L1, L2, W1, and W2, are 90, 59, 47, and 26 millimeters, respectively.
• As stated above,mask portion430 may be formed by a process called rotational molding.FIG. 8A shows a top view of amold800 that may be used to producemask portion430 by rotational molding.FIG. 8B shows a sectional view ofmold800 taken along theline8B-8B as indicated inFIG. 8A.FIGS. 8C and 8D show perspective views ofmold800. As shown inFIG. 8A, themold800 is symmetric about anaxis802. As shown best inFIGS. 8C and 8D,mold800 includes atop piece810 and abottom piece812. When thetop piece810 andbottom piece812 are bolted or clamped together, they cooperatively define a hollowinterior volume820 as shown inFIG. 8B.Interior walls830 of themold800 define the boundaries of hollowinterior volume820.
• Oneportion822 of theinterior volume820 has a generally toroidal shape corresponding to the generally toroidal shape of theinflated cuff460. Anotherportion824 of theinterior volume820 has a generally elliptical shape corresponding to the shape ofplate440. That is,portion824 defines a hollow volume, the shape of which is substantially identical to the flat, elliptical shape ofplate440. Similarly, theportion822 defines a hollow volume, the shape of which is substantially identical to the shape of theinflated cuff460.
• In operation,mask portion430 may be formed by adding or injecting a liquid plastic material (e.g., polyvinyl chloride or “PVC”) into theinterior volume820 ofmold800 and by then rotating or otherwise movingmold800 so as to coat theinterior walls830 with the liquid plastic material. Preferably, themold800 is simultaneously rotated about two axes that are at ninety degrees to each other (e.g.,axis802 and another axis that is perpendicular to axis802). While themold800 is rotating, centrifugal forces cause the liquid plastic material to coat all portions of theinterior walls830 ofmold800. After all portions of theinterior walls830 have been so coated, the mold is then preferably held stationary in the position illustrated inFIG. 8B. That is, themold800 is preferably oriented so that theportion824 of thehollow interior820 is at the bottom of the mold (i.e., so thatportion824 is parallel to the ground and is closer to the ground, or lower, than any other portion of the hollow interior820) while themold800 is held stationary. While themold800 is held in this stationary position, most of the liquid plastic material drains, or flows, down along theinterior walls830 into theportion824. However, all of the liquid plastic material does not flow intoportion824. Rather, surface tension or other forces cause a thin coating of the liquid plastic material to remain in contact with theinterior walls830 that define theportion822. Themold800 is preferably held stationary long enough for the plastic material to cure and solidify before the mold is opened by separating the top andbottom pieces810,812.
• The material that filledportion824 forms theplate440 of themask portion430. The thin coating of plastic material that lined theinterior walls830 ofportion822 forms acuff460 that is integrally attached to theplate440. Air trapped within theinterior volume820 while themask portion430 is being formed becomes trapped within thecuff460. So, when themask portion430 is removed frommold800, thecuff460 is partially inflated. Thecuff460 is only partially inflated (rather than fully inflated) when themask portion430 is removed frommold800 because, as the mold cools, the trapped air shrinks in volume and accordingly only partially fills the interior volume defined by thecuff460.
• It will be appreciated that a variety of materials may be introduced into themold800 and used to formmask portion430. The term liquid plastic material as used herein to refers to any material that is capable of curing from a liquid or fluid state to a solid, flexible or plastic, state. Due to its flexibility, resistance to stretching, and ability to define complex shapes such as that ofinflated cuff460, polyvinyl chloride is a preferred material to use as the liquid plastic material that formsmask portion430. However, it will be appreciated that other materials could also be used.
• Once themold800 has been opened and the cured plastic plate and cuff have been removed, fabrication ofmask portion430 may be completed by addinginflation tube490. It will be appreciated that addinginflation tube490 is a relatively simple step and is accomplished by forming an aperture inplate440 that extends from thepharyngeal side444 through the plate and into the interior volume defined bycuff460, and then fixinginflation tube490 to that aperture. Alternatively, as will be discussed below, it may sometimes be advantageous to provide amask portion430 that does not include an inflation tube. In these cases, fabrication of the mask portion is complete as soon as the cured, integrally formed,plate440 andcuff460 have been removed from themold800.
• The cured mask portion is preferably relatively soft and flexible. In one exemplary embodiment, the durometer of the curedmask portion430 is fifty five plus or minus ten on the Shore A scale of hardness. More preferably, the durometer of the curedmask portion430 is fifty five plus or minus five on the Shore A scale of hardness. Most preferably, the durometer of the curedmask portion430 is substantially equal to fifty five on the Shore A scale of hardness.
• FIG. 9A shows a side view ofairway tube410, which includes aconnector section411 and an integral tube andbackplate section416.FIG. 9B shows a perspective view ofconnector section411.FIGS. 9C and 9D show views ofconnector section411 taken in the directions indicated bylines9C-9C and9D-9D, respectively, as shown inFIG. 9B.FIG. 9E shows a side view of integral tube andbackplate section416.FIGS. 9F and 9G show two perspective views of integral tube andbackplate section416.
• Referring toFIGS. 9B, 9C, and9D,connector section411 includes aproximal portion412 and adistal portion413.Proximal portion412 is preferably cylindrical and configured to couple to standard medical ventilating, or anaesthetic devices.Distal portion413 is preferably oblong as shown best in the perspective view ofFIG. 9B.Connector section411 further includes a disk shaped plate, or flange,414 that extends around the junction ofproximal portion412 anddistal portion413.Connector section411 also defines a sealedinternal airway passage415 that extends entirely through theproximal portion412 and thedistal portion413. In theproximal portion412, the cross section of thepassage415 is circular, and in thedistal portion413, the cross section of thepassage415 is oblong.
• Referring toFIGS. 9E, 9F, and9G, integral airway tube andbackplate section416 includes aproximal portion417, a central orcurved portion418, and abackplate portion419. A disk shaped plate, or flange,420 is integrally attached to the proximal end ofproximal portion417.Section416 defines a hollowinternal passage421 that extends entirely through the proximal, curved, andbackplate portions417,418,419.
• Airway tube410 is assembled by coupling theconnector section411 and the integral airway tube andbackplate section416 together. As shown inFIG. 9A, when the parts are so coupled, theflange414 ofconnector section411 abuts theflange420 ofsection416. Also, thedistal portion413 ofconnector section411 extends telescopically into the portion ofinternal passage421 that is defined byproximal portion417 ofsection416. Also, theinternal passage415 ofconnector section411 communicates with theinternal passage421 ofsection416 so that theairway tube410 defines a continuous sealed internal passage424 (shown for example inFIGS. 10A and 10B) that extends from the tube's proximal end to the tube's distal end.Airway tube410 also defines a left side410-l, a right side410-r(shown for example inFIG. 9F), an inner side410-i, and an outer side410-o(shown for example inFIG. 9E). Note that the left and right sides are defined with respect to a person (e.g., a physician) that is inserting the laryngeal mask airway device into a patient and that the left side410-lof the tube will actually be disposed on the right side of the patient's natural airway when the device is in the fully inserted configuration.
• Backplate portion419 defines alaryngeal side422 and apharyngeal side423. When thedevice400 is assembled, thelaryngeal side422 ofbackplate portion419 is attached or fixed to thepharyngeal side444 ofmask portion430. Also, when the assembleddevice400 is in the fully inserted configuration, thepharyngeal side423 of thebackplate portion419 contacts the pharyngeal wall of the patient. Whendevice400 is assembled, theinternal passage424 oftube410 communicates with the passage defined bymask portion430 and thedevice400 defines a sealed airway passage that extends from the proximal end of thetube410 to thecentral aperture442 ofmask portion430.
• Theairway tube410 is sized so that when the laryngeal mask airway device is in the fully inserted configuration, theproximal portion417 of the airway tube will be disposed between the patient's upper and lower teeth.FIG. 10A shows a cross-sectional view of theproximal section417 into which theconnector section411 has been inserted taken along theline10A-10A as shown inFIG. 9A. Theairway tube410 is also sized so that when the device is in the fully inserted configuration, thecentral portion418 will extend through the patient's natural upper airway between the laryngeal inlet and the patient's teeth.FIG. 10B shows a cross sectional view of thecentral portion418 taken along theline10B-10B as shown inFIG. 9A. As shown inFIG. 10B (as well asFIGS. 9A and 9E),airway tube410 defineslongitudinal folds425 that extend along the left and right sides of the central andbackplate portions418,419.
• Connector section411 and integral tube andbackplate section416 ofairway tube410 are preferably formed using molding techniques such as injection or rotational molding. In one exemplary embodiment,connector section411 is formed from polycarbonate and the material ofsection411 is characterized by a durometer of 95 Shore A. Integral tube andbackplate section416 is preferably formed from a flexible plastic material (e.g., PVC) and is characterized by a durometer of 86 plus or minus 15 or 20 Shore A. More preferably, the material of integral tube andbackplate section416 is characterized by a durometer of 86 plus or minus 7 (or plus or minus ten percent) Shore A. Still more preferably, the material of integral tube andbackplate section416 is characterized by a durometer of 86 plus or minus 3.5 (or plus or minus 5 percent) Shore A. Most preferably, the material of integral tube andbackplate section416 is characterized by a durometer that is substantially equal to 86 Shore A.
• Connector section411 is preferably relatively hard so that (1) it is easy to reliably attach theproximal portion412 ofsection411 to standard breathing apparatus and (2) patient's can bite down on thedistal portion413 without causing collapse or shrinkage of the internal airway passage provided bysection411. Note that when the device is in the fully inserted configuration, the patient's teeth will contactproximal portion417 of the integral tube and backplate section rather thansection411, because the distal portion ofsection411 extends into theproximal portion417 as illustrated inFIG. 9A. However, pressure applied by the patient's teeth will be transferred tosection411, andsection411 is preferably sufficiently hard to resist this pressure without allowing theinternal passage415 to collapse.
• Section416 is preferably softer thansection411 to facilitate bending thesection416 as necessary to insert the device into a patient and to permit unhindered flexion and extension of the patient's neck whiledevice400 is in the fully inserted configuration. However, as will be discussed below,section416 is preferably stiff enough, at least at room temperature, so that laryngeal mask airway devices constructed according to the invention may be inserted by applying pressure tosection416 without requiring insertion of a finger into the patient's mouth.
• Returning toFIGS. 4A-4C, it can be seen thatdevice400 may be formed by fixing or attaching theairway tube410 to themask portion430. More specifically, the laryngeal side of the backplate portion of the airway tube is attached to the pharyngeal side of the mask portion so that the outer perimeter of thelaryngeal side422 of the backplate portion surrounds thecentral aperture442 of theplate440. Theairway tube410 may be attached to themask portion430 by heat sealing, gluing, or otherwise bonding or fixing the two components together.
• As shown for example inFIG. 9F, thebackplate portion419 defines a “dome shaped” or “bowl shaped” interior volume. When thebackplate portion419 is attached to themask portion430, thebackplate portion419 andmask portion430 cooperatively define a hollow bowl shaped interior volume as shown for example inFIG. 4C. As will be discussed below, portions of the larynx extend into this bowl shaped volume when the device is in the fully inserted configuration.
• One advantage ofdevice400 is that it is relatively simple and inexpensive to produce. As discussed above, both themask portion430 and theairway tube410 may be produced using a rotational molding process. Theairway tube410 may alternatively be produced using injection molding. Each of these steps (i.e., producing themask portion430 and producing the airway tube410) is relatively simple and inexpensive. Fabrication of thedevice400 may be completed by adding an inflation tube to mask portion430 (in embodiments that use inflation tubes) and by attaching theairway tube410 to themask portion430. Accordingly,devices400 may be fabricated at very low cost. This low cost of fabrication enables laryngeal mask airway devices constructed according to the invention to be used as disposable devices. That is, the economics of constructing laryngeal mask airway devices according to the invention, such asdevice400, enable them to be used once and then discarded.
• Several structural advantages of laryngeal mask airway devices constructed according to the invention will now be discussed. As shown for example inFIGS. 4A-4C and9A, thebackplate portion419 essentially forms a backplate of thedevice400. In most prior art laryngeal mask airway device constructions (e.g., as shown inFIG. 3), the mask portion includes a backplate and defines a cylindrical aperture for receiving, or connecting with, a cylindrical airway tube. Forming the mask portion with an added backplate disadvantageously increases (1) the mechanical complexity of the mask portion and (2) the cost of fabricating the mask portion. Also, the junction, which is found in prior art laryngeal mask airway devices, of a cylindrical airway tube and a cylindrical aperture in a backplate tends to form a relatively stiff construction. For example, in the device illustrated inFIG. 3, it is relatively difficult to compress the junction of the cylindrical airway tube and the backplate in the direction indicated byarrows260. Accordingly, this portion of prior art laryngeal mask airway device constructions disadvantageously forms a relatively thick, incompressible, structure that must be pushed between the patient's upper and lower teeth and past the patient's throat to insert the device. In contrast to those prior art constructions, the mask portions of laryngeal mask airway devices constructed according to the invention are formed without backplates (e.g., as shown inmask portion430 inFIGS. 5A-5D) and the backplate of the device is provided by the airway tube. It is less complex, and less expensive, to provide the backplate as part of the airway tube. Also, eliminating the telescopic junction of two cylindrical components that characterized the prior art make laryngeal mask airway devices constructed according to the invention more compressible and easier to insert into patients. For example, referring toFIG. 4A, the backplate ofdevice400 compresses in the direction indicated byarrows260 more easily than prior art laryngeal mask airway devices. This facilitates pushing laryngeal mask airway devices constructed according to the invention between the patient's upper and lower teeth and past the patient's throat.
• In addition to providing a backplate, the general shape of theairway tube410 distinguishesdevice400 from prior art laryngeal mask airway devices. In most prior art laryngeal mask airway devices (e.g., as shown inFIGS. 1 and 3), the airway tube is cylindrical. While cylindrical airway tubes have functioned well for many years in many different models of laryngeal mask airway devices, the cylindrical configuration has some disadvantages. One critical feature for an airway tube of any laryngeal mask airway device is the size of the internal airway passage. This passage must be large enough to provide adequate ventilation of the patient's lungs. That is, moderate pressure differentials (e.g., a pressure drop of one to two cm H₂O) between the proximal and distal ends of the airway tube should be sufficient for moving a volume of air through the tube that is sufficiently large for adequately ventilating the patient's lungs. With a cylindrical airway tube it is easy to calculate the volume of air that can be moved through the tube for any given pressure differential, and the volume can be adjusted simply by adjusting (i.e., increasing or decreasing) the radius of the internal airway passage.
• However, one constraint that should be considered in the design of airway tubes is that these tubes will extend through the patient's mouth, between the patient's upper and lower teeth, for as long as the laryngeal mask airway device remains in the fully inserted configuration. So, while a laryngeal mask airway device is inserted into a patient, the patient's mouth must remain opened wide enough to create an inter-dental gap (i.e., space between the upper and lower teeth) that is big enough to accommodate the airway tube. Holding the mouth open for long periods of time so as to create a large inter-dental gap can cause discomfort to the patient post operatively. More importantly, some patients cannot open their mouths wide enough to permit easy insertion of adequate sized cylindrical tubes. Accordingly, one disadvantage of cylindrical airway tubes is that they require a larger inter-dental gap than would a tube that had a flatter, or more oblong, cross section.
• Another constraint that should be considered in the design of airway tubes is that these tubes will extend through the patient's natural upper airway for as long as the laryngeal mask airway device remains in the fully inserted configuration. This natural, or anatomical, upper airway, which is formed by several anatomical structures including the pharyngeal wall, hard and soft palates, and tongue, is not itself cylindrical. Accordingly, a cylindrical airway tube does not form a “good fit” with the anatomical upper airway. For example, when a cylindrical tube is extended through the anatomical upper airway, the tube tends to contact only isolated portions of the anatomical structures that define the anatomical upper airway. Accordingly, more pressure is applied to those structures, and those structures are subjected to more trauma, than would be the case if the shape of the tube better matched the shape of the anatomical upper airway.
• As shown inFIGS. 9A, 9E,9F, and9G, the proximal andcentral portions417,418 of theairway tube410 are oblong or flattened rather than cylindrical. As will be discussed in greater detail below, this advantageously (1) maximizes the size of the tube's internal airway passage; (2) minimizes the intra-dental gap required for accommodating the airway tube; and (3) allows the tube to fit well within, or match, the patient's natural airway.
• As stated above, theairway tube410 is sized so that theproximal section417 will be disposed between the patient's upper and lower teeth when the laryngeal mask airway device is in the fully inserted configuration. As shown inFIG. 10A, the inter-dental gap G required to accommodateproximal section417 is narrower than would be required if theproximal section417 were cylindrical. Rather than a circular cross section, the cross section of theinternal airway passage424 is oblong. In one exemplary embodiment, the thickness G of theproximal section417 is about 13.0 millimeters. The cross-sectional area of the internal passage defined byairway tube410 is preferably at least as large as that of a cylindrical tube with a nine millimeter internal diameter passage. As shown inFIG. 10A, the width of theinternal passage424 may be referred to as W3 and the thickness of theinternal passage424 may be referred to as T6. In one exemplary embodiment, W3 and T6 are 20.0 and 6.7 millimeters, respectively.
• As also stated above, theairway tube410 is sized so that thecentral portion418 will extend through the patient's anatomical upper airway while the laryngeal mask airway device is in the fully inserted configuration. As shown inFIG. 10B, the cross-section of thecentral portion418 is oblong rather than cylindrical. Accordingly, thecentral portion418 provides a “better fit” to the anatomical airway than do cylindrical tubes. As shown inFIG. 10B, the width of the central portion of the airway tube may be referred to as W4 and the thickness of the central portion of the airway tube may be referred to as T7. One preferred value for W4 is 23.7 millimeters plus or minus 10 percent (or plus or minus 2.37 millimeters) and one preferred value for T7 is 10.3 millimeters plus or minus 10 percent (or plus or minus 1.03 millimeters). More preferably, W4 and T7 are equal to 23.7 millimeters plus or minus 5 percent and 10.3 millimeters plus or minus 5 percent, respectively. Even more preferably, W4 and T7 are substantially equal to 23.7 millimeters and 10.3 millimeters, respectively. Also, the width W4 of the central portion of the airway tube is preferably equal to the thickness T7 times a factor of two, plus or minus ten percent (i.e., W4=(2±0.2)·T7). More preferably, the width W4 is equal to the thickness T7 times a factor of two, plus or minus five percent (i.e., W4=(2±0.1)·T7).
• As shown inFIG. 2, the airway tube of any laryngeal mask airway device must follow a curve (about an axis extending in the left-to-right direction) from the point where it couples to the mask portion to the point where the patient's teeth contact the tube. This curve enables the tube to extend through the patient's natural upper airway from the teeth to the laryngeal inlet. One important design consideration for an airway tube of any laryngeal mask airway device is that the airway tube should be designed so that it does not form “kinks” when it is bent, or curved, as necessary for inserting the device into a patient.
• FIG. 11 shows an example of a tube that has formed akink1102 as a result of bending the tube by an extreme amount. As is well known, the size of the internal passageway defined by any tube is dramatically decreased at anysuch kinks1102. The effects of kinks in tubes is commonly experienced in connection with garden hoses. For example, formation of a single kink in a garden hose can dramatically decrease the amount of water that can pass through the hose and be distributed by a sprinkler. The effects of kinks are similar in laryngeal mask airway devices. Any kinks forming in the airway tube of a laryngeal mask airway device essentially close off the tube's airway passage and dramatically decrease the volume of air that can pass through the tube. Accordingly, it is very important to design the airway tube so that kinks in the tube do not form when the tube is inserted into a patient.
• One advantage of cylindrical airway tubes over tubes with flatter, or more oblong, cross sections is that for any given amount of bend, the cylindrical tube is less likely to form a kink. To reduce the risk thatairway tube410 forms any kinks,tube410 is preferably provided with twolongitudinal folds425 that extend along the left and right sides of the tube's central andbackplate portions418,419. As shown inFIG. 10B, the cross-section of thelongitudinal fold425 that extends along the left side of the airway tube defines a recess, or groove425-gthat extends from the left exterior edge of the airway tube towards the center of the tube in the left-to-right direction. Similarly, the cross-section of thefold425 that extends along the right side of the airway tube defines a recess that extends from the right exterior edge of the airway tube towards the center of the tube in the right-to-left direction. Each of the recesses defines an upper exterior surface425-uand a lower exterior surface425-l. The thickness of the longitudinal folds425 (i.e., the thickness as measured in a direction extending from the inner side410-ito the outer side410-oof the airway tube) may be referred to as T12 and the thickness of thelongitudinal folds425 as measured in the left-to-right direction may be referred to as T13. In one exemplary embodiment, the thickness T12 and T13 are about three millimeters and 2.7 millimeters, respectively.
• As indicated inFIG. 10B, bending of the tube410 (about an axis extending in the left-to-right direction) caused by inserting the laryngeal mask airway device through the patient's anatomical airway generates compressive forces in the directions indicated byarrows260. Thelongitudinal folds425 tend to prevent localized collapse of theinternal passage424 as a result of bending the tube. If thetube410 is subjected to compressive forces in the direction ofarrows260 sufficiently large to deform the tube, the tube may deform to the shape illustrated inFIG. 10C. As shown, the deformation of the tube in the region of thelongitudinal folds425 may be likened to the movement of an accordion or concertina. The size of theinternal passage424 does decrease as the tube compresses from the profile shown inFIG. 10B to the profile shown inFIG. 10C. However, once the airway tube has reached the configuration shown inFIG. 10C, thelongitudinal folds425 resist additional decreases in the size of thepassage424, even in response to additional compression of the tube. So,airway tube410 advantageously (1) reduces the size of the inter-dental gap required for accommodating the tube; (2) provides a large airway passage; (3) decreases the likelihood that the tube will form kinks when the laryngeal mask airway device is inserted into a patient; (4) decreases the likelihood that the tube will form kinks in response to bending of the patient's neck over the likely range of head movement; and (5) fits well within the patient's anatomical airway.
• Another advantage of thelongitudinal folds425 is that they provide a convenient groove425-gfor locating theinflation tube490.FIG. 12 shows a perspective view of adevice400 constructed according to the invention in which theinflation tube490 has been glued into the groove425-gthat extends along the right side of the airway tube.
• Another important feature of theairway tube410 is the degree of curvature through which thecentral portion418 extends. As discussed in U.S. Pat. No. 6,079,409 (entitled, “Intubating laryngeal mask”), there is an optimum degree of curvature for the airway tube of a laryngeal mask airway device that will allow the patient to remain in a “neutral position” while the device is in the fully inserted configuration. The neutral position is a position in which the patient is lying on their back and in which the patient's head is positioned, for example with a pillow, so that the geometric relation of the head to the rest of the body is the same as when the patient is standing upright and looking forward. The device disclosed in the '409 patent used a rigid airway tube, and as discussed in that application, for rigid airway tubes the optimum degree of curvature is between 125 and 135 degrees. This degree of curvature permits the patient to remain in the neutral position while the laryngeal mask airway device is being inserted and after the device has been placed in the fully inserted configuration.
• For convenience of exposition, the shape assumed byairway tube410 when the tube is not subjected to any external forces shall be referred to as the “preformed configuration”. As will be discussed below, since theairway tube410 is somewhat flexible, it can deviate from the preformed configuration when the laryngeal mask airway device is in use.FIG. 9E shows the integral tube andbackplate section416 in its preformed configuration. As shown, theairway tube410 is preferably manufactured so that when it is not subjected to any external forces, thecentral portion418 follows a circular curve about an axis C (the axis C extending in the left-to-right direction and being perpendicular to the plane of the page inFIG. 9E) from a proximal limit ofcurvature426 to a distal limit ofcurvature427. In one exemplary embodiment, the angle theta between two rays extending from the axis C to the proximal anddistal limits426,427 for the preformed configuration is 105 degrees plus or minus ten degrees. More preferably, the angle theta for the preformed configuration is 105 degrees plus or minus five degrees. Even more preferably, the angle theta is substantially equal to 105 degrees. In one exemplary embodiment of an adult female size, the distance, or radius, R₁, between the axis C and the inner surface410-iofairway tube410 for the preformed configuration is substantially equal to forty millimeters plus or minus about three millimeters, and the distance, or radius, R₂, between the axis C and the outer surface410-oofairway tube410 for the preformed configuration is substantially equal to fifty millimeters plus or minus about three millimeters.
• The preferred degree of curvature for the preformed configuration ofdevice400 is different than for the rigid tube laryngeal mask airway device disclosed in the above-referenced '409 patent. This difference in curvature facilitates insertion ofdevice400. When a laryngeal mask airway device is inserted into a patient, proper insertion begins by placing the mask portion into the patient's mouth so that the pharyngeal side of the mask is in contact with the patient's hard palate. At this point, in devices designed according to the '409 patent, the curve in the rigid airway tube forces the proximal end of the airway tube to be pushed against the patient's chest. Positioning the end of the tube against the patient's chest makes inserting the device somewhat more difficult than if the proximal end could be positioned at a location that was spaced apart from the patient's body. However, the requirements of a rigid airway tube (which facilitates later insertion of an endotracheal tube) and allowing the patient to remain in a neutral position before, during, and after insertion, necessitates positioning the airway tube's proximal end against the patient's chest at the beginning of insertion.
• Like the laryngeal mask airway device of the '409 patent,device400 allows the patient to remain in a neutral position before, during, and after insertion. However, unlike the device of the '409 patent, the proximal end of the airway tube ofdevice400 need not be positioned against the patient's body at any time during insertion. If theairway tube410 ofdevice400 were rigid and were formed with the above-discussed preformed configuration, then the patient could not remain in a neutral position while the laryngeal mask airway device was in the fully inserted configuration. Rather, the patient's head would have to be tilted backwards to allow the airway tube to fit into the patient's anatomical airway. However, since theairway tube410 is not rigid, the tube can flex, or bend, slightly away from the preformed configuration as it is being inserted thereby allowing the tube to fit into the anatomical airway of a patient that is in the neutral position. The curve of the preformed configuration of thecentral portion418 of the airway tube preferably does not deviate far from the anatomical curve of 125 to 135 degrees so that the tube need not bend much to fit into the anatomical airway. However, the curve of the preformed configuration of thecentral portion418 preferably deviates somewhat from the anatomical curve of 125 to 135 degrees so as to eliminate the need for pressing the tube's proximal end against the patient's chest during insertion.
• FIG. 13 shows in solid lines a side view of integral tube andbackplate section416 in the preformed configuration.FIG. 13 also shows in dotted lines the shape that integral tube andbackplate section416 assumes after thedevice400 has been located in the fully inserted configuration within a patient that is resting in the neutral position. As shown, theairway tube410 bends about an axis extending in the left-to-right direction when the laryngeal mask airway device is inserted into a patient. When the laryngeal mask airway device is inserted into a patient, the center or curvature, or axis about which the tube bends, shifts from C to C′, and the angle through which the tube bends changes from the 105 degrees (plus or minus five or ten degrees) of the preformed configuration to the 125 to 135 degrees required to fit within the anatomical airway of a patient lying in the neutral position.
• As discussed above, in one exemplary embodiment, the integral airway tube andbackplate section416 is formed from polyvinyl chloride. This material is relatively stiff at room temperature but becomes much more flexible at body temperature. So, the airway tube is relatively stiff as thedevice400 is being inserted into the patient. However, after thedevice400 has been placed in the fully inserted configuration for a while (e.g., three to five minutes), the airway tube softens and becomes more pliable so that its shape easily accommodates to the shape of the patient's anatomical airway without placing undue force against the anatomical structures that define the anatomical airway. Also, since the material is relatively stiff at room temperature, the airway tube is generally stiff enough to act as an insertion tool. That is,device400 may be entirely controlled during insertion simply by manipulating the portions of theairway tube410 that extend outside of the patient's mouth. This eliminates the need for inserting a finger into the patient's mouth while inserting the laryngeal mask airway device and further eliminates the need for additional insertion tools.
• Another important advantage ofdevice400 relates to the quality of the seal provided with the laryngeal inlet. As shown inFIG. 4A, there is a relatively large empty space S behind themask portion430. The empty space behindmask portion430 is substantially larger than that provided by prior art laryngeal mask airway devices and, as will be discussed below, advantageously allowsdevice400 to provide improved seals.
• As shown inFIG. 4A, the space S is defined by the distance T9 between the laryngeal side of the proximal end of the inflated cuff and theairway tube410 as measured in the laryngeal-to-pharyngeal direction. A preferred value for the distance T9, when the airway tube is in the preformed configuration, is 32 millimeters plus or minus 3 millimeters. More preferably, the distance T9, when the airway tube is in the preformed configuration, is 32 millimeters plus or minus 2 millimeters. Even more preferably, the distance T9, when the airway tube is in the preformed configuration, is substantially equal to 32 millimeters.
• Whendevice400 is in the fully inserted configuration, the posterior portion of the patient's tongue rests in the space S. As will be discussed below, enlarging the space S in which the tongue rests improves the quality of the seal between the proximal end of the inflated cuff and the patient's laryngeal inlet.
• FIG. 14 shows a view of an inflated cuff of a laryngeal mask airway device, and the illustrated cuff has been divided into three different regions. When the device is located in the fully inserted configuration, each region of the cuff contacts a different portion of the patient's anatomy.Region1, at the cuff's proximal end, fits into the patient's valleculae (i.e., the space behind the lower part of the tongue).Region2, which is disposed between the cuff's proximal and distal ends, contacts the patient's pyriform fossae, which are symmetrically disposed on either side of the patient's glottic opening.Region3, which is disposed at the cuff's distal end, contacts the patient's cricoid cartilage. Accordingly, when the laryngeal mask airway device is inserted into a patient, a seal that extends continuously around the patient's glottic opening is formed by contact between the inflated cuff and the patient's valleculae, pyriform fossae, and cricoid cartilage.
• FIG. 15A shows a prior art laryngealmask airway device1500 that has been placed in the fully inserted configuration. As shown, theinflated cuff1502 has formed a seal around the patient's glottic opening thereby coupling the passage of theairway tube1504 to the patient'strachea1506. The laryngeal side of the proximal portion of the cuff fits into the patient'svalleculae1508, and the laryngeal side of the distal portion of the cuff contacts the patient'scricoid cartilage1510. The patient'stongue1512 is disposed generally along the inner, or anterior, side of the airway tube between the patient's teeth and the proximal end of the inflated cuff. Theposterior portion1514 of the patient'stongue1512 is disposed in the space S (between the proximal end of the inflated cuff and the inner, or anterior, side of the airway tube). The dashedline1516 illustrates the contour thetongue1512 would follow if thedevice1500 were not inserted into the patient. As shown, insertion of the laryngeal mask airway device displaces thetongue1512 in the pharyngeal-to-laryngeal direction away from the natural position indicated by dashedline1516. Pushing the tongue in this direction also pushes or levers portions of the larynx in the pharyngeal-to-laryngeal direction and thereby tends to prevent the cuff from fitting tightly around the larynx. This weakens the seal provided by the laryngeal mask airway device by decreasing pressure between the cuff and anatomical structures such as the pyriform fossae.
• FIG. 15B showsdevice400 in the fully inserted configuration. The dashedline1602 represents the contour assumed by the tongue whenprior art device1500 is in the fully inserted configuration. As shown, the enlarged empty space S provided bydevice400 allows the tongue to assume a more natural position thanprior art device1500. In particular, the enlarged empty space S ofdevice400 allows the tongue to be displaced in the laryngeal-to-pharyngeal direction from where the tongue would be ifdevice1500 were in the fully inserted configuration. Allowing the tongue to assume a more natural position also allows other anatomical structures to assume a more natural position (i.e., to be displaced in the laryngeal-to-pharyngeal direction from where they would be ifdevice1500 were in the fully inserted configuration) and thereby improves the seal provided bydevice400.
• As is well known, portions of the larynx (e.g., the ariepiglottic folds) can extend into the bowl shaped space bounded by the inflated cuff when a laryngeal mask airway device is in the fully inserted configuration.FIG. 15B suggests this by showingstructures1530 extending into the bowl-shaped volume defined by the cuff and backplate ofdevice400. Enlarging the space S also has the beneficial effect of increasing the size of the bowl-shaped volume defined by device400 (i.e., increasing the empty space that is bounded by the backplate portion and the inflated cuff of device400). This also improves the quality of the seal provided bydevice400 by allowing the larynx to extend further into the bowl-shaped volume than was possible with prior art laryngeal mask airway devices. Allowing the larynx to extend further into this space allows the larynx to assume a more natural position (i.e., a position similar to the position the larynx would occupy if the laryngeal mask airway device were not inserted) and improves the seal provided by the laryngeal mask airway device.
• Several features ofdevice400 cooperate to provide the enlarged empty space S. First, as shown inFIG. 5A, the thickness T5 of the proximal portion of the mask portion is substantially thicker than the thickness T4 of the distal portion of the mask portion. Another feature that cooperates to define the enlarged empty space S is the angle between thecentral portion418 and thebackplate portion419 of the airway tube. As shown inFIG. 4A, at the junction of thecentral portion418 and thebackplate portion419, thecentral portion418 extends at an angle alpha with respect to theplate440. In one exemplary embodiment, the angle alpha is equal to ten degrees plus or minus two degrees. More preferably, the angle alpha is equal to ten degrees plus or minus one degree. Even more preferably, the angle alpha is substantially equal to ten degrees. This angle provides additional clearance between the proximal end of the plate and the inner side of the airway tube as measured in the laryngeal-to-pharyngeal direction. Yet another feature that contributes to defining the empty space is an absence of an inflation tube in the space. In most prior art laryngeal mask airway devices, as shown for example inFIG. 3, the inflation tube extends from the proximal end of the cuff in the distal-to-proximal direction into the space. However, indevice400, as shown for example inFIG. 12, the inflation tube does not extend from the proximal end of the cuff and instead extends from the pharyngeal side of the plate to one of thenotches425 without entering the space S.
• As discussed above, and as illustrated inFIGS. 5A-5C and15B, one feature that helps define the enlarged empty space S is the increased thickness of the proximal end of the inflated cuff. Whendevice400 is in the fully inserted configuration, the inflatable cuff may preferably be inflated to a pressure of about 60 cm HO.
• The pressure in silicone cuffs tends to increase during surgical procedures because commonly used anesthesia gasses (e.g., nitrous oxide) tend to diffuse through the semi-permeable cuff wall. One advantage of formingmask portion430 out of PVC is that the anesthesia gasses do not tend to diffuse into the cuff and change the intra-cuff pressure during a surgical procedure.
• Yet another advantage ofdevice400 relates to the ease with which it can be inserted into a patient.FIG. 16A shows a side view ofdevice400 when thecuff460 is deflated.FIGS. 16B and 16C show perspective views ofdevice400 when thecuff460 is deflated. The thickness T3 (as shown inFIG. 6) of the cuff is sufficiently thin, that when thecuff460 is deflated, the profile of the distal portion of the laryngeal mask airway device is almost entirely determined by theplate440 of the mask portion and thebackplate portion419 of the airway tube. As shown inFIG. 16A, the thickness T10 of the distal end, as measured in the laryngeal-to-pharyngeal direction, is virtually entirely determined by the thickness of theplate440. The thickness of the deflated laryngeal mask airway device, as measured in the laryngeal-to-pharyngeal direction, gradually increases with increases in the distal-to-proximal direction until the thickest point, at the proximal end of the mask portion, is reached which has a thickness T11, as measured in the laryngeal-to-pharyngeal direction. The rate of increase in thickness is determined by the angle theta between theplate440 and the pharyngeal side ofbackplate portion418. In exemplary embodiments, the angle theta is about eleven degrees and the thickness T10 is about two millimeters (i.e., the deflated cuff adds virtually no thickness beyond the thickness of the plate T2). The thickness T11 is preferably about seventeen millimeters plus or minus two millimeters. More preferably, the thickness T11 is about seventeen millimeters plus or minus one millimeter. Even more preferably, the thickness T11 is substantially equal to seventeen millimeters. The thickness T11, which is the thickest part of deflateddevice400 as measured in the laryngeal-to-pharyngeal direction, is relatively thin as compared with prior art laryngeal mask airway devices, which are usually about twenty-six millimeters thick in comparable sizes.
• FIG. 16C illustrates the size of the deflateddevice400 as measured in the left-to-right direction. The width of the distal tip of the laryngeal mask airway device is relatively narrow and the width of the device gradually increases with increases in the distal-to-proximal direction. The width of the widest part of the deflated laryngeal mask airway device, as measured in the left-to-right direction, W1 is equal to the width of the widest part of the plate (as shown inFIG. 5E).
• The overall profile ofdeflated device400, as measured in the laryngeal-to-pharyngeal direction, as well as the left-to-right direction, is small as compared with prior art deflated laryngeal mask airway devices. Having such a small profile greatly increases the ease with whichdeflated device400 may be inserted into a patient. In particular, the thin profile, as measured in the laryngeal-to-pharyngeal direction, makes it very easy to push the deflated mask portion and backplate between a patient's upper and lower teeth and past the patient's throat. The thin profile also increases the likelihood that the deflated mask portion will fit between the pharyngeal wall and the epiglottis without disturbing or otherwise pushing on the epiglottis as the distal tip of the mask portion is being pushed past the epiglottis towards the esophageal sphincter.
• FIG. 17 shows adeflated device400 that has been partially inserted into a patient that is resting in the neutral position. As shown, thedistal tip434 of the deflated laryngeal mask airway device has fit between the patient's pharyngeal wall1078 and theepiglottis1710. When an unconscious patient lies on their back, relaxation of the muscles tends to allow the back of the tongue and the epiglottis to drop down towards the pharyngeal wall, thereby reducing or minimizing the space between the epiglottis and the pharyngeal wall. Accordingly, the thinner the deflated laryngeal mask airway device, the more likely it is that the device will fit into the space between the pharyngeal wall and the epiglottis without pushing on or otherwise moving the epiglottis. The slim profile ofdeflated device400 accordingly facilitates proper insertion of the device.
• One problem with prior art laryngeal mask airway devices is that they are often inserted improperly. As discussed above, the laryngeal mask airway device is a “forgiving” device and tends to establish an airway even when the device is improperly inserted. However, ideally, the laryngeal mask airway device should be inserted properly so that the epiglottis is not disturbed and so that the distal tip of the device is disposed adjacent the esophageal sphincter. One problem that contributes to the difficulty of inserting prior art laryngeal mask airway devices relates to the profile assumed by the deflated cuff. In prior art laryngeal mask airway devices, the deflated cuff forms a “structural component” of the device in that (1) a significant portion of the profile of a deflated prior art laryngeal mask airway device is determined by the cuff and (2) the shape of the deflated cuff significantly affects the path taken by the device through the body as it is inserted into a patient. Accordingly, proper insertion of a prior art laryngeal mask airway device generally requires properly forming, or shaping, the cuff as it is deflated. U.S. Pat. No. 5,711,293 discloses an example of a prior art forming tool for forming a laryngeal mask airway device into an ideal shape for insertion as the cuff is being deflated.
• Indevice400, the deflated cuff contributes only insignificantly to the profile of the deflated laryngeal mask airway device. Rather, the profile of the deflated device is determined almost entirely by theplate440 ofmask portion430 and thebackplate portion419 ofairway tube410. As shown inFIG. 16A-C, these components define a slim profile that facilitates proper insertion of the device.
• Another advantage ofdevice400 relates to the profile of the device when deflated as compared with the profile of the device when inflated. As discussed above, whendevice400 is deflated it presents a slim, thin, or small profile as compared with prior art laryngeal mask airway devices. However, whendevice400 is inflated, the cuff expands considerably and, as discussed above, this allows the device to provide an improved seal with the tissues surrounding the patient's glottic opening. The relatively large difference between the thickness (as measured in the laryngeal-to-pharyngeal direction) of the deflated device as compared with the thickness of the inflated device distinguishesdevice400 from prior art laryngeal mask airway devices. As discussed above, the thickest part of the deflateddevice400, T11, is about seventeen millimeters. The thickest part of theinflated device400, T5, is about 25.4 millimeters. Accordingly, the thickest part of theinflated device400 is approximately 1.5 times larger than the thickest part of the deflateddevice400. Although 1.5 is a preferred factor for distinguishing the thickest parts of the inflated and deflated device, it may be preferable for the thickest part of the inflated device to be 1.5, plus or minus 0.15, times larger than the thickest part of the deflated device (i.e., T5=(1.5±0.15)·T11).
• As shown inFIG. 17, any laryngeal mask airway device will bend or flex as the device is being inserted into a patient. More specifically, as the distal tip of the laryngeal mask airway device contacts the patient's palato-pharyngeal arch, the distal tip bends down towards the larynx (or bends about an axis that extends in the left to right direction). As the device is inserted further into the patient, the portion of the device that is proximal to the palato-pharyngeal arch will bend around the arch and portions of the device that have already passed by the palato-pharyngeal arch will straighten out. In this manner, the point of bending or flexing begins at the laryngeal mask airway device's distal tip and moves backwards in the distal-to-proximal direction as the device continues to be inserted into the patient.
• As shown for example inFIG. 16B, thebackplate portion419 ofdevice400 is “spear shaped” or tapered in that its width decreases with increases in the proximal-to-distal direction. The very narrow width of the backplate's distal tip makes the device's distal tip relatively flexible so that the distal tip easily bends or flexes downwards towards the larynx as thedevice400 is inserted into the patient. As thedevice400 is inserted further, and the device's resistance to bending increases in a linear fashion due to the gradual widening of the “spear shaped” backplate portion. This linear increase in resistance to bending about an axis that extends in the left-to-right direction is an advantageous feature ofdevice400. If the increase in resistance were not linear and instead increased suddenly or dramatically (in a non-linear fashion) at one or more points as the device was being inserted, the device would tend to kink, or form a localized fold, instead of bending smoothly around the palato-pharyngeal arch. Such a kink-like deformation would be more stimulating to the patient and increase the likelihood of malposition and/or trauma during insertion. Some prior art laryngeal mask airway devices are capable of offering a substantially linear increase in resistance to bending as the device is inserted into a patient as long as the cuff has been properly deflated and formed into a proper configuration. However, since the cuff of these prior art laryngeal mask airway devices forms a structural component of the device, they do not offer a linear increase in resistance to bending, and tend to form kinks while being inserted, when the cuff is deflated without proper use of a forming tool. One advantage ofdevice400 is that the laryngeal mask airway device will provide the desired substantially linear increase in resistance to bending regardless of the manner in which the cuff is deflated. This is so because the deflated cuff does not contribute significantly to the structure of the device and the device's resistance to bending is virtually entirely determined by the geometry of thebackplate portion419.
• Yet another advantage ofdevice400 relates to the size of the inflated cuff. As shown for example inFIGS. 5A and 15A, the thickness T5, as measured in the pharyngeal-to-laryngeal direction, of the proximal end of the inflated cuff is relatively large as compared with prior art laryngeal mask airway devices. The relatively large thickness T5 of the proximal end of the inflated cuff advantageously increases the separation between the epiglottis and theaperture442 ofplate440 and thereby decreases the likelihood that the epiglottis can block the airway provided by thedevice400. Prior art laryngeal mask airway devices often included “bars” or “slits” disposed in the mask portion to prevent the epiglottis from blocking the airway of the device. Such bars are disclosed for example in U.S. Pat. No. 5,297,547 (see FIG. 8 of the '547 patent). Although laryngeal mask airway devices constructed according to the invention could include such “bars”,device400 advantageously eliminates the need for such bars and accordingly may be manufactured less expensively.
• Returning toFIG. 17, as shown the distal tip ofdevice400 has passed through the gap between the epiglottis and the pharyngeal wall. Sometimes the distal tip of the device will catch on the epiglottis as the device is being inserted and will push the epiglottis into a “down folded” condition. In such a “down folded” condition, the epiglottis may block the trachea or the airway provided by a laryngeal mask airway device. Another advantage ofdevice400 is that thecuff460 can lift a down folded, or posterior lying, epiglottis forwards, or anteriorly, thereby keeping the airway clear.FIG. 7B illustrates a preferred folded configuration for the deflated cuff. As shown, when thecuff460 is deflated, the extra or loose material of the cuff may be folded towards the center of the mask portion so that the deflated cuff covers the entire, or nearly the entire,central aperture442 ofplate440. If the cuff is folded into this position so that it covers the entire, or nearly the entire,central aperture442, then thecuff460 will advantageously lift the epiglottis anteriorly and thereby open the airway as the cuff is inflated.
• One disadvantage of prior art re-usable laryngeal mask airway devices is that after every sterilization, the cuff must be deflated and the device must be configured for insertion into a patient. Unfortunately, most physicians who use laryngeal mask airway devices lack the skill or dedication required to pack the device into the optimal configuration for facilitating insertion. Another advantage ofdevice400 is that when it is used as a disposable device, the laryngeal mask airway device may be packaged and sold in a configuration that is optimal for facilitating insertion of the device into a patient. As discussed above,device400 is advantageous because (1) the deflated cuff only adds a small amount of thickness to the mask portion and (2) the deflated cuff may be configured for lifting a down folded or posterior lying epiglottis out of the way. Preferably, thedevice400 is placed into this optimal configuration (i.e., with the cuff deflated and folded as discussed above in connection withFIGS. 7A and 7B) prior to sale and then packaged into a sterile bag or package (e.g., a sterile plastic bag). So, when a physician wishes to insert a laryngeal mask airway device into a patient, the physician may simply remove a device from its sterile packaging and insert it into the patient without having to first deflate or reposition the cuff.
• As discussed above, in some embodiments ofdevice400 aninflation tube490 need not be provided. So, in embodiments that do not include inflation tubes, fabrication of the laryngeal mask airway device is completed by attaching the airway tube to the partially inflated mask portion after the mask portion is removed from the mold. Whenmask portion430 is formed by rotational molding, the cuff is partially inflated when the mask portion is removed from the mold. The amount of air that is trapped in the cuff during fabrication is similar to the amount of air that is normally injected into the cuff via the inflation tube after the mask portion has been inserted into a patient to achieve the desired intra-cuff pressure of 60 cm H₂O. Accordingly, such a partially inflated cuff is capable of forming an effective seal around a patient's laryngeal inlet.
• These masks have one principal disadvantage as compared with embodiments ofdevice400 that do include an inflation tube. The profile of the partially inflated cuff is thicker, as measured in the proximal-to-distal direction, than is achievable indevice400 when the cuff is fully deflated via the inflation tube, and this can make inserting the laryngeal mask airway device more difficult. However, laryngeal mask airway devices that do not include an inflation tube do have one principal advantage. Namely, they can be easier and faster to use in emergency situations because the practitioner need not bother with deflating or inflating the cuff, and the airway is established as soon as the mask portion is inserted into the patient's pharynx. The thicker profile can complicate insertion of such a laryngeal mask airway device. However, two factors make the insertion easier than might otherwise be the case. First, in unconscious patients, the muscles of the body become very relaxed which can make it easier to push a thick profile device through the upper and lower teeth and down the throat. Second, since the cuff is only partially inflated, and since the cuff is very thin and flexible, a very small amount of pressure applied to one portion of the cuff will squeeze, or shrink the size of that portion, and force air trapped in the cuff into other portions of the cuff thereby inflating or expanding those other portions. For example, the proximal end of the cuff will expand if the distal end is squeezed flat, and only a very small pressure is required to squeeze the distal end into a flat shape. As adevice400 with a partially inflated cuff is inserted into a patient, some parts of the cuff may expand while other parts are squeezed by anatomical structures. However, the ability to shrink in some places while expanding in others makes it relatively easy to push the partially inflated cuff into the patient's pharynx.
• Accordingly, one method of making a laryngeal mask airway device according to the invention is to (1)produce mask portion430 using the rotational molding process described above in connection withFIGS. 8A-8D; (2) removemask portion430 from themold800; and (3) attach an airway tube to the mask portion. The rotational molding process produces a partially inflated mask portion that is inflated to a suitable degree. Once the airway tube is attached to the mask portion, fabrication of the laryngeal mask airway device is complete. An inflation tube need not be added. The completed laryngeal mask airway device may be packaged for sale in a sterile bag. Such laryngeal mask airway devices may be very useful for emergency situations, for example for use by emergency workers in ambulances or emergency wards.
• FIG. 18A shows a side view of another embodiment of a laryngealmask airway device1800 constructed according to the invention.FIGS. 18B and 18C show two perspective views ofdevice1800. As shown,device1800 is very similar todevice400. Bothdevice1800 anddevice400 includeidentical mask portions430. Also, the backplate of bothdevices1800 and400 are very similar. The principal difference between the two devices is in the airway tube.
• Theairway tube1810 ofdevice1800 is a double barreled tube.FIG. 18D shows a sectional view ofairway tube1810 taken in the direction indicated byline18D-18D as shown inFIG. 18A.Airway tube1810 includes aleft tube1812 and aright tube1814. The tubes are fixed, bonded, or extruded together at a central joint1816 that extends from the proximal ends to the distal ends of the two tubes.Airway tube1810 also defines an inner side1810-iand an outer side1810-o.
• As withairway tube410,tube1810 has an overall oblong or flattened cross section. Accordingly, tube1810 (like tube410), fits relatively well within the patient's anatomical airway and minimizes the intra-dental gap required to accommodate the tube. Also as withtube410,airway tube1810 includes aproximal portion1820, acentral portion1822, and abackplate portion1824.Backplate portion1824 is almost identical tobackplate portion419. The only principal difference between the two backplate portions is how they couple to their respective central portions of the airway tube.
• As shown inFIG. 18D, the junction of the twocylindrical tubes1812 and1814 at the joint1816 forms two grooves, or recesses,1830,1832 in the airway tube. Thegroove1830 extends along the inner side1810-iof the airway tube and thegroove1832 extends along the outer side1810-oof the tube. One advantage oftube1810 is that thegroove1830 can serve as a guide for guiding subsequently inserted tubes, such as for example an endotracheal tube. That is, afterdevice1800 has been positioned in the fully inserted configuration, thegroove1830 can be used to guide a subsequently inserted device.FIG. 19A shows a perspective view of an endotracheal tube being guided bygroove1830 as the endotracheal tube is inserted into the patient's body (not shown).
• Embodiments ofdevice1800 that are used to guide a subsequently inserted endotracheal tube (or some other kind of tube), preferably define a “gap”, or aperture, between the mask portion and the backplate portion at the proximal end of the mask portion. When the distal tip of the endotracheal tube reaches the mask portion's proximal end, continued insertion of the endotracheal tube will push the endotracheal tube's distal end through the gap between the mask portion and the backplate of the device and enable the endotracheal tube's distal end to proceed through theaperture442 of the mask portion and into the patient's trachea.
• FIG. 19B shows an embodiment ofdevice1800 that defines such agap1910. Bothdevice400 anddevice1800 are constructed by attaching or bonding the outer perimeter of the laryngeal side of the backplate portion of the airway tube to the pharyngeal side of theplate440 of themask portion430. In the case ofdevice400, the entire outer perimeter of the backplate portion is so attached to theplate440. However, in the case ofdevice1800, one portion of the outer perimeter of the backplate (at the backplate's proximal end) is not bonded to theplate440 and the rest of the outer perimeter of the backplate is bonded to theplate440. Since the proximal ends of the backplate andplate440 are not bonded together, pressure on theplate440 can push theplate440 of the mask portion away from the backplate and create thegap1910. In the absence of downward pressure on theplate440, the portions of the backplate andplate440 that are bonded together tend to hold the unbonded portions together as well. The effect is to create a laryngeal mask airway device that has a “flap valve”. Under normal conditions, theplate440 and backplate ofdevice1800 remain in contact as in the case ofdevice400. Also, whendevice1800 is in the fully inserted configuration, pressure exerted by the patient's pharyngeal and laryngeal walls tends to push theplate440 and backplate towards one another, or together. However, indevice1800, pressure on the proximal end of the mask portion (generated for example by subsequent insertion of an endotracheal tube that is guided by groove1830) can push theplate440 away from the backplate to generate thegap1910. Subsequently inserted endotracheal tubes can extend throughgap1910 and then throughaperture442 and into the patient's trachea.
• FIG. 20 shows a perspective view of an alternative embodiment of amask portion430′ that may be used in laryngeal mask airway devices constructed according to the invention.Mask portion430′ is similar tomask portion430, however, the pharyngeal side of theplate440′ ofmask portion430′ is not flat and instead defines a step, or recess,2010, that extends around the elliptical central aperture of the mask portion. It will be appreciated that therecess2010 may be used to properly locate the backplate portion of the airway tube when the backplate portion is fixed to the mask portion. Preferably, the laryngeal side of the backplate portion is bonded or fixed to the bottom of therecess2010. When the backplate portion is fixed to the bottom ofrecess2010, asmall portion2012 at the distal end of theplate440′ separates the distal tip of the backplate portion from the distal tip of the laryngeal mask airway device. This may be advantageous because the airway tube is generally harder and stiffer than the mask portion. So, as the laryngeal mask airway device is inserted into a patient, and the device's distal tip contacts anatomical structures within the patient's natural airway, the contact is between the patient and the relatively soft mask portion rather than between the patient and the harder backplate portion.Mask portion430′ thereby advantageously provides a simple mechanism for properly locating the backplate portion when the laryngeal mask airway device is being assembled and also protects the patient from potential traumatic contact with the relatively hard distal tip of the backplate portion as the device is being inserted. It will be appreciated thatmask portion430′ may be used in place ofmask portion430 indevice400,device1800, or any other laryngeal mask airway devices constructed according to the invention.
• As discussed above in connection withFIGS. 10B and 10C, the longitudinal folds in the airway tube permit the tube to compress somewhat in a concertina or accordion like fashion. Another advantage of the longitudinal folds is that they can permit the airway tube to expand in response to forces applied to the interior of the tube. This expansion can advantageously permit the airway tube to accommodate a subsequently inserted endotracheal tube and thereby allowsdevice400 to function as an intubating laryngeal mask airway device.FIG. 10D shows a side view of an embodiment ofdevice400 into which anendotracheal tube1010 has been inserted. To reach the configuration illustrated inFIG. 10D, thedistal end1012 ofendotracheal tube1010 was inserted into the proximal end of integral tube andbackplate section416 and advanced through thesection416 until thedistal end1012 emerged through the aperture in themask portion430 as shown. As theendotracheal tube1010 advances through integral tube andbackplate section416, the longitudinal folds in thesection416 allow thesection416 to expand and thereby accommodate the endotracheal tube.
• It will be appreciated that whendevice400 is used as an intubating laryngeal mask airway device, it may be desirable to use alternative embodiments of theairway tube410 or the integral tube andbackplate section416. For example, the integral tube andbackplate section416 shown inFIG. 10D includes two longitudinal folds that extend down the left and right sides of the tube rather than the single fold provided in thesection416 illustrated inFIGS. 10B and 10C.FIG. 10E shows a cross section of thesection416 taken in the direction ofline10E-10E as shown inFIG. 10D.FIG. 10E shows the two longitudinal folds that extend down the left and right sides of the integral tube and backplate section.FIG. 10E shows the integral tube and backplate section in an expanded condition. That is, the longitudinal folds have expanded in a concertina like fashion to accommodate the subsequently inserted endotracheal tube. It will be appreciated that airway tubes constructed according to the invention may be provided with one, two, or more longitudinal folds that extend down the left and right sides of the tube.
• In addition to including extra longitudinal folds, it will be appreciated that it may be advantageous for the airway tube, or integral tube and backplate section, of intubating laryngeal mask airway devices constructed according to the invention to include a modified proximal end that is cylindrical or otherwise wide enough to accommodate insertion of an endotracheal tube as shown inFIG. 10D.
• FIG. 10F shows a side view of another embodiment ofdevice400 constructed according to the invention, andFIG. 10G shows a perspective view of the embodiment shown inFIG. 10F. In the illustrated embodiment, the airway tube includes aridge1020.Ridge1020 extends in the proximal-to-distal direction from a point near the middle of thebackplate portion419 to a point in thecurved portion418 that is proximal to a junction of thebackplate portion419 and thecurved portion418.Ridge1020 also extends from the outer side of the tube410-ointo the interior of the passage defined by the tube. In this embodiment, the walls of the tube near the junction of thecurved portion418 and thebackplate portion419 are also preferably weaker than the walls in other portions of the tube. For example, the tube wall can be made thinner in this region to weaken this portion of the tube.
• The embodiment illustrated inFIGS. 10F and 10G facilitates rotating the patient's head while the laryngeal mask airway device is in the fully inserted configuration. For example, the device may be placed in the fully inserted configuration while the patient is resting in the neutral position (i.e., the patient will be lying on their back and the patient's nose will be the part of the patient's head that is furthest from the ground). Once the laryngeal mask airway device is so located, it may be desirable to rotate the patient's head. For example, if the patient's ear is being operated on, it may be desirable to rotate the patient's head approximately ninety degrees so that instead of the patient's nose, the patient's ear is now the part of the patient's head that is furthest from the ground. It will be appreciated that this exposes the ear and makes it easier to operate on the ear. Ideally, rotating the patient's head in this manner while the laryngeal mask airway device is located in the fully inserted configuration (1) will not disturb the seal between the inflated cuff and the tissues surrounding the patient's glottic opening and (2) will not cause a collapse of the internal passage provided by the airway tube. Weakening the walls of the airway tube near the junction of thebackplate portion419 and thecurved portion418 allows the distal part of the laryngeal mask airway device (i.e., the mask portion and the backplate portion) to rotate with respect to the remainder of the airway tube without placing undue force on the inflated cuff, and this tends to preserve the seal between the cuff and the tissues surrounding the glottic opening when the patient's head is so rotated.Ridge1020 tends to prevent the internal passage provided by the airway tube from collapsing when the patient's head is so rotated and the airway tube is correspondingly twisted.
• FIGS. 21 and 22 show another embodiment of a laryngeal mask airway device constructed according to the invention. In this embodiment, anair inlet tube10 will be understood to provide air (or other gas) service to a patient's lungs viamask structure11 and the patient's trachea. As best seen inFIG. 22, base structure of themask11 comprises a relatively stiffly pliantskeletal base12 of generally elliptical configuration, a portion of this base being viewable directly through a draftsman's break through a collapsed thin-filminflatable envelope13, which will be understood to be inflatable by external supply of inflation air via aflexible inflation line15;line15 will be understood to include a conventional two-way check valve (not shown) for purposes of holding an inflated condition of the envelope13 (as inFIG. 21) or for holding a deflated condition of the envelope (as inFIG. 22). Theenvelope13 is merely an inflatable portion of a single-part, integrally formed, total enclosure served by the inflation/deflation line15, being the product of a so-called rotational-molding process, wherein a single plastic material in liquid state is caused to progressively build a thin layer or film of cured plastic material against and throughout the internal surface area of a given annular mould cavity, the gravitationally drained remained of the liquid-phase plastic being allowed to cure in situ as the relatively stiff skeletal annular member of the laryngeal mask airway device, at the bottom of the mould. The cured product of such moulding not only provides the indicated skeletal-base function but also, between the inner and outer peripheries of the skeletal annulus provides the additional function of completing, as a skeletal annulus, the inflatable and peripherally yieldable enclosure of envelope provided by the moulded film. For the case of the described integrally formed component (12/13) when formed of suitable plastic such as polyvinylchloride, the thin film at13 is typically of thickness in the order of 0.1 to 0.3 mm, while theskeletal base12 may be typically 10 to 20 times the moulded thickness of thefilm13. Such film will be understood to collapse and flatter or mat itself at random in response to deflation action vialine15. It is to be understood that while it is possible to form theskeletal base12 as flat and of relatively uniform thickness, it is also possible to use the described moulding process to develop a skeletal-base thickness which varies as a function of longitudinal progression, as from a relatively thick proximal location (e.g., 2-3 mm thick) to a much reduced distal-end thickness (e.g., 1-mm), thereby according a desired distal-end bendability which can usefully serve the process of installing the laryngeal mask airway device in the patient. Such a proximal-to-distal thickness variation is later indicated inFIG. 25 (at12′) as a feature of the device ofFIGS. 23 and 24.
• To complete a description of the laryngeal mask airway device ofFIGS. 21 and 22, theairway tube10 is shown to be supported on and by its overlap with posterior surface of the proximal region of the annulus ofskeletal base12, the distallyopen end16 of the airway tube having preferably an angularly truncated configuration, which is open within the generallyelliptical lumen17 of theskeletal base12. Finally, closure of the posterior side of the mask structure is effected by a tent-like roof18 of flexible plastic sheet material, wherein the lapped distal portion of the airway tube is analogous to a ridge pole, so that the tent-like roof sheeting slopes away from its longitudinally central support by the distal end of the airway tube, to its peripherally sealed engagement to the rim of the skeletal base, as seen inFIG. 21, it being understood that sheeting18 is also suitably draped and sealed at its proximal-end closure around theairway tube10.
• FIGS. 23 and 24 are recognizable for their resemblance toFIGS. 21 and 22, except for the additional provision of a gastric-drainage tube20, in side-by-side bonded relation to anairway tube21, which may in all respects be as described forairway tube10 ofFIGS. 21 and 22, except for the fact thattubes20/21 are symmetrically and oppositely offset from the longitudinal sagittal plane of the generally elliptical configuration ofmask structure22. This symmetrical relation is seen to continue until the distallyopen end23 of theairway tube21 is positioned to vent over thelumen24 of the generally elliptical annularskeletal base25 of the mask structure. As with the laryngeal mask airway device ofFIGS. 21 and 22, the baseskeletal member25 may be a product of a rotational moulding operation wherein a thin-film inflatable/deflatableannular envelope26 is integrally formed therewith, with provision for selective inflation/deflation action via aflexible line15, as also inFIGS. 21 and 22.
• For gastric-drainage purposes, and as better seen in FIGS.25 to29, thedrainage tube20 is seen inFIG. 26 to undergo a mild zig-zag course change, from lateral offset adjacency toairway tube21 to its distal-end alignment of symmetry with respect to the sagittal plane of the mask. Within the distal half of theskeletal base25, and the distal end ofdrainage tube20 passes through thebase25 and projects its angularly truncatedopen end27 slightly beyond the distal end ofbase25.
• As previously noted, the longitudinal progression of reducing thickness ofskeletal base25 in the distal direction enables a more pliant action to be inherently imparted to the distal half of the mask.FIG. 25 also illustrates that the inflated sectional area of the inflated thin-film envelope26 is similarly and progressively decreased in the distal direction, so thattubes20,21 may be oriented at proximal departure from the mask to incorporate a preferred angle α in therange 20° to 30°, at commencement of their proximal course over the tongue, for air (gas) and gastric servicing connections (not shown), as necessary outside the patient's mouth.
• As with the laryngeal mask airway device ofFIGS. 21 and 22, the structure ofFIGS. 23 and 24 may be completed with a tent-like closure28 of the posterior side of the mask. Again, such closure is realized by pliant sheet material which inFIG. 28 is seen to derive “ridge-pole” support fromtube20, centered on the distal-half ofskeletal base25. InFIG. 29, the section shows thetent closure28 to be supported over theadjacent tubes20,21 at passage over thelumen24 of the mask, with the skirt of tent sheeting peripherally secured toskeletal base25, it being again understood that at its proximal end, the tent sheeting is also conformed and sealed to bothtubes20,21 to complete closure of the posterior side of the mask.
• InFIG. 28, a bulging profile inphantom outline30 on the anterior side of the mask will be understood to suggest film-envelope inflation away from the anterior surface ofskeletal base25, and afurther inflation profile31 in phantom outline on the posterior surface of the mask will be understood to suggest aninflatable cuff31 over the periphery ofbase25, to provide cushioned reference of the mask to the back wall of the patient's pharynx. As shown, the back-cushion material is shown for its further connection totent28 along the sagittal-plane intercept withtent28.
• It is desired that for ease of installation of the mask in a patient, that the deflated condition should offer a minimum thickness dimension. this will be clear fromFIGS. 28 and 29 where the respective minimum dimensions D1, D2 are to be compared with maximum available inflation dimensions D3, D4 without theback cushion31, and D5, D6 with theback cushion31.
• In the embodiment of FIGS.30 to32, the simplest difference to note is that theskeletal base40 is flat and its integrally formed thin-filminflatable envelope portion41 is otherwise as described for theinflatable film26 ofFIG. 25. Also, thedistal portion42 of thedrainage tube43 is locally bent for straight but inclined passage through a similarly inclined orientingopening44 in the distal-end region ofbase40. At remaining overlap with the proximal-end region ofbase40, thedrainage tube43 is laterally offset to the extent that it can symmetrically pair withairway tube44, and bothtubes43,44 can be bonded to the supporting flat posterior surface ofbase40. Tentlike sheet material described for closure of the posterior side of the mask can be as described for FIGS.25 to29, it being noted that at section a-a ofFIG. 30, the local section bears an almost identically similar appearance to that depicted inFIG. 28 for the mask ofFIG. 27.
• According to one technique of manufacture of theunitary base40 with integrally moulded thin-film envelope portion41, this single component is depicted in the longitudinal section ofFIG. 21 and in the plan view ofFIG. 22, it being understood that such passages as at43′ (for drainage-tube passage as at43′, for drainage-tube orientation), at45 (for inflation-air access), and at46 (for lumen definition) are the product of known core-pin and other mould-feature defining structures of the mould as an entirety. The preassembly oftubes43,44 in side-by-side adjacency, together with the pre-bent and truncated open distal end ofdrainage tube43 are later assembled for adhesively or otherwise sealed passage of the distal end of thedrainage tube43 and for film-pierced and peripherally sealed passage of the truncated distal end oftube43 into the relationship depicted inFIG. 30.
• In an alternative mode of structural assembly, depicted inFIG. 31A, a preformed and suitably bent distal-end fitting50, for later assembly to the remainder of the drainage tube (not shown) is an insert part which in the process of rotation-moulding becomes theFIG. 31A part to be later assembled to mask parts that become a laryngeal mask airway device with the gastric-drainage feature. To this end, the preassembled drainage andairway tubes43,44 will be understood to terminate over thelumen46 and that the distally projecting end of the drainage-tube portion (43) of this tube (43,44) preassembly may be suitably fitted to the open proximal end of fitting50, to establish continuity of the full drainage-tube function. Such continuity may be provided by known techniques of telescoping fit, as to the extent denoted by dottedline51 inFIG. 31A, or by a short sleeve of heat-shrink plastic material (not shown) which laps the abutting ends of equal diameter tubular ends, namely the proximal end of fitting50 to the distal end of the two-tube preassembly (43,44).
• The plan view ofskeletal base40′ ofFIG. 33 will be recognized as identical to that ofFIG. 32, except that two spaced elongateparallel bars55,56 Symmetrically straddle the longitudinal sagittal plane of the mask (not shown) into which this component can be integrated. The purpose served bybars55,56 is to provide a measure of support for thedrainage tube43 as it passes over the lumen and as it alters course for distal-end symmetrical orientation with respect to the sagittal plane.
• FIG. 34A shows a side view of another embodiment of a laryngealmask airway device3400 constructed according to the invention.FIGS. 34B and 34C show perspective views ofdevice3400.Device3400 is similar to the above-discussed device400 (shown for example inFIGS. 4A-4C).Device3400 includes anairway tube3410, amask portion3430, and aninflation tube3490. Reference characters for describing components ofdevice3400 have been generally selected to correspond to those used above to describe device400 (e.g., the mask portion indevice3400 has been designated3430 whereas the mask portion ofdevice400, shown for example inFIG. 4A, has been designated430).
• FIG. 35A shows a side view ofmask portion3430 when the cuff is inflated.FIG. 35B shows a view of the anterior side ofmask portion3430 taken in the direction ofline35B-35B as shown inFIG. 35A.FIG. 35C shows a perspective view of the anterior side ofmask portion3430.FIG. 35D shows a view of the posterior side ofmask portion3430 taken in the direction ofline35D-35D as shown inFIG. 35A.FIG. 35E shows a sectional view ofmask portion3430 taken in the direction ofline35E-35E as shown inFIG. 35A.
• As with mask portion430 (shown, for example, inFIG. 5A),mask portion3430 includes aplate3440, aninflatable cuff3460, and aninflation line3490. However, as shown best inFIGS. 35A, 35D, and35E,mask portion3430 also includes asupport3470. As will be discussed in greater detail below,support3470 advantageously (1) increases the structural integrity ofmask portion3430 without detrimentally affecting the ease of insertion ofdevice3400 and (2) prevents the epiglottis from obstructing the airway provided bydevice3400.
• One method of formingmask portion3430 so that it includessupport3470 will now be discussed. As discussed above, mask portion430 (shown, for example, inFIG. 5D) is preferably constructed using a rotational molding technique, andmask portion430 is formed so that theplate440 defines acentral aperture442.Mask portion3430 is also preferably formed using the same rotational molding technique described above in connection withmask portion430, however, the rotational molds may be altered so thatplate3440 is solid and does not define a central aperture. With reference toFIG. 35D, after themask portion3430 has cured and has been removed from the rotational mold,support3470 may be defined by cutting a horseshoe shapednotch3472 intoplate3440.Apertures3478 are also provided insupport3470. At itsdistal end3474,support3470 is contiguous with, and an integral part of,plate3440. However, the horseshoe shapednotch3472 permits theproximal end3476 ofsupport3470, as well as all portions ofsupport3470 that are detached fromplate3470 bynotch3472, to flap up and down with respect to the rest ofplate3440. Once horseshoe shapednotch3472 has been cut inplate3440, thecuff3460 is preferably inflated and then theproximal end3476 ofsupport3470 is pushed into the bowl shaped aperture defined by theinflated cuff3460. Once thesupport3470 has been located within the aperture defined by the inflated cuff as shown inFIGS. 35A and 35E, theouter periphery3480 ofsupport3470 is preferably bonded (e.g., by ultrasonic welding or use of adhesives), to the inner periphery, or inner wall,3462 ofcuff3460.
• As shown inFIG. 35E, theinflated cuff3460 may be thought of as defining aninner wall3462 and anouter wall3464. Theinner wall3462 andouter wall3464 are separated by an elliptical cylinder indicated inFIG. 35E by dashedlines3468. This elliptical cylinder is also indicated by the dashedline3468 inFIG. 35B. It will be appreciated that while cylinders are characterized by a circular cross section, the elliptical cylinder indicated by dashedlines3468 is characterized by a generally elliptical, or oblong, cross section. Returning toFIG. 35E, it will be appreciated that the central opening defined by the generally toroidalinflated cuff3460 is bounded by theinner wall3462 of thecuff3460.Support3470 is preferably bonded to thecuff3460 at some points along the cuff'sinner wall3462.
• Since thesupport3470 is bonded to thecuff3460, deflation of thecuff3460 causes thecuff3460 to draw thesupport3470 in the laryngeal-to-pharyngeal direction so that thesupport3470 is nearly parallel toplate3440. In practice, whencuff3460 is fully deflated,support3470 tends to be slightly offset in the pharyngeal-to-laryngeal direction from plate3440 (or aboveplate3440 whenmask portion3430 is in the orientation shown inFIG. 35A). Conversely, inflation of thecuff3460 causes thecuff3460 to pull thesupport3470 in the pharyngeal-to-laryngeal direction so thatsupport3470 is angled with respect toplate3440 as shown inFIG. 35A.
• When a laryngeal mask airway device is in the fully inserted configuration, muscular contraction in the region of the larynx can generate forces in the direction of arrows F as shown inFIG. 35B. These forces bias the inflated cuff towards themidline3431 of the mask portion. If these forces become strong enough, movement of the inflated cuff towards themidline3431 and can reduce the size of, or obstruct, the airway provided by the laryngeal mask airway device. Indevice3400,support3470 advantageously resists movement of the inflated cuff in the direction of the arrows F and thereby acts as a counterbalance to these forces.
• Another way to make the mask portion resist forces in the direction of arrows F that does not involve use ofsupport3470 is simply to make the mask portion out of a stiffer material. However, although making the mask portion stiffer would have the beneficial effect of resisting those forces, it would also make the mask portion less pliable and therefore would disadvantageously make the mask portion less amenable to insertion into the airway of a patient. As discussed above in connection withFIG. 17, the mask portion of a laryngeal mask airway device is preferably capable of bending around an axis extending in the left-to-right direction to facilitate insertion into a patient without damaging the structures that define the patient's anatomical airway. Presence ofsupport3470 does not appreciably increase the amount of force required to make themask portion3430 bend around an axis extending in the left-to-right direction (as shown inFIG. 17). So,support3470 increases the structural integrity of mask portion3430 (by increasing the mask portion's resistance to forces applied in the direction of the arrows F shown inFIG. 35B) without making it more difficult to insertdevice3400 into a patient.
• Another function ofsupport3470 relates to obstruction of the airway by the epiglottis. As is known, one potential drawback to laryngeal mask airway devices is that, when the patient is reclining on their back, the epiglottis sometimes drops down into the aperture defined by the inflated cuff and blocks the airway provided by the device. U.S. Pat. No. 5,297,547 is one example of a patent that discloses using an apertured sheet to prevent the epiglottis from obstructing the airway of a laryngeal mask airway device. Indevice3400, if the epiglottis drops down, rather than falling into the passage defined by airway tube3410 (shown for example inFIG. 34A), the epiglottis will come to rest onsupport3470. Theapertures3478 are sufficiently long so that, although the epiglottis may obstruct a portion of theapertures3478, it will not cover, or obstruct, all of theapertures3478, and theuncovered portions3478 effectively prevent the epiglottis from obstructing the airway provided bydevice3400.
• In contrast to prior art epiglottis supports,support3470 is attached to theinner wall3462 ofcuff3460. Due to this attachment, the cuff, when inflated, tends to holdsupport3470 in a desired location. If the epiglottis, or any other portion of the anatomy, biases support3470 in the laryngeal-to-pharyngeal direction, the cuff tends to holdsupport3470 in position and resists movement of the support. Thecuff3460 in effect provides an air cushioned support for thesupport3470.
• As discussed above, one method of formingmask portion3430 is to formplate3440 without a central aperture and to then definesupport3470 by cutting the horseshoe shapednotch3472 into theplate3440. In the preferred method of manufacture,mask portion3430 is formed by rotational molding andsupport3470 is formed during the rotational molding simultaneously with the rest ofmask portion3430.FIG. 36 shows a sectional view of amold800′ that may be used to formmask portion3430. Mold800′ is similar to the mold800 (shown inFIGS. 8A-8D), and includes atop piece810′ and abottom piece812′. Unlikemold800, inmold800′, thebottom piece812′ defines arecess814. Aftermold800′ has been moved or rotated so as to coat all interior walls with the liquid plastic material used to form the mask portion,mold800′ is held in the position shown inFIG. 36 until the liquid plastic material has cured. The presence ofrecess814 allows the liquid plastic material to simultaneously formplate3440 andsupport3470. Whenmask portion3430 is initially removed frommold800′, thesupport3470 is still connected to plate3440 by a thin layer of cured liquid plastic material. This thin layer ofmaterial connecting plate3440 andsupport3470 extends generally along the outline of horseshoe shapednotch3472 as shown inFIG. 35D.Support3470 can be easily separated fromplate3440 simply by pulling on thesupport3470 enough to tear this thin layer of cured material. This tearing effectively forms horseshoe shapednotch3472. It will be appreciated that such a procedure is simpler and less expensive than cutting horseshoe shapednotch3472 out of a substantially flat plate. It will also be appreciated thatmold800′ preferably includes features that define theapertures3478 ofsupport3470. Oncesupport3470 is so formed, it is then preferably attached to the inner wall3642 of the inflated cuff as described above.
• Airway tube3410 will now be discussed. As with airway tube410 (shown, e.g., inFIGS. 4A-4C),airway tube3410 preferably includes two components: aconnector section3411 and an integral tube andbackplate section3416.FIG. 37A shows a side view of tube andbackplate section3416.FIG. 37B shows a view of the anterior side of tube andbackplate section3416.FIGS. 37C and 37D show sectional views taken along thelines37C-37C and37D-37D, respectively, as shown inFIG. 37A.FIG. 38A shows a perspective view ofconnector section3411.FIGS. 38B and 38C show sectional views ofconnector section3411 taken in the direction oflines38B-38B and38C-38C, respectively, as shown inFIG. 38A.FIG. 38D shows an end view of the proximal end ofconnector section3411 taken in the direction indicated byline38D-38D as shown inFIG. 38A.
• It will be appreciated thatconnector section3411 is similar to connector section411 (shown, e.g., inFIG. 9B) and that integral tube andbackplate section3416 is similar to section416 (shown, e.g., inFIG. 9E). Some of the common features ofconnector sections3411,411 and integral tube andbackplate sections3416,416 will now be described. Referring toFIGS. 38A-38D,connector section3411 includes aproximal portion3412 and adistal portion3413.Proximal portion3412 is preferably cylindrical and configured to couple to standard ventilating or anaesthetic devices.Distal portion3413 is preferably oblong.Connector section3411 further includes a disk shaped plate, or flange,3414.Connector section3411 defines a sealedinternal airway passage3415 that extends entirely throughproximal portion3412 anddistal portion3413. In theproximal portion3412, the cross section ofpassage3415 is circular and indistal portion3413, the cross section ofpassage3415 is oblong.
• Referring toFIGS. 37A-37D, integral airway tube andbackplate section3416 includes aproximal portion3417, a central orcurved portion3418, and abackplate portion3419.Section3416 defines a hollowinternal passage3421 that extends entirely throughproximal portion3417,central portion3418, andbackplate portion3419.Section3416 defines a left side3410-land a right side3410-r(shown for example as shown inFIG. 37B).Section3416 also defines an inner side3410-iand an outer, or convex, side3410-o(shown for example as shown inFIG. 37A). As shown for example inFIGS. 34A and 37D, thecentral portion3418 of integral tube andbackplate section3416 definelongitudinal folds3425 that extend along the left and right sides of thecentral portion3418 and into thebackplate portion3419.
• Airway tube3410 is assembled by couplingconnector section3411 and integral tube andbackplate section3416 together. As shown inFIG. 34A, when the parts are so coupled,flange3414 of connector section abuts theproximal end3420 of integral tube andbackplate section3416. Also, thedistal portion3413 ofconnector section3411 telescopically extends into theinternal passage3421 defined by theproximal portion3417 of integral tube andbackplate section3416. Whenconnector section3411 andsection3416 are assembled, theinternal passage3415 ofconnector section3411 communicates with theinternal passage3421 of integral tube andbackplate section3416 so thatairway tube3410 defines a continuous sealed internal passage that extends from the tube's proximal end to the tube's distal end.
• Whenconnector section3411 is fully inserted intoproximal portion3417 to assembleairway tube3410, the distal end ofconnector section3411 is located at the point3411-das indicated inFIG. 37A. So, whenairway tube3410 is assembled, the airway tube's internal passage is defined by (1)passage3415 ofconnector section3411, which extends from the proximal end ofairway tube3410 to point3411-dand (2) the portion ofpassage3421 of integral tube andbackplate section3416, which extends from point3411-dto thebackplate portion3419. In other words, since thedistal portion3413 ofconnector section3411 is telescopically inserted intoproximal portion3417, the portion ofinternal passage3421 defined byproximal portion3417 extending from theproximal end3420 ofsection3416 to the point3411-d, does not define the internal airway passage ofairway tube3410 and instead defines a passage designed for receiving thedistal portion3413 ofconnector section3411. With reference toFIG. 34A, in one exemplary embodiment of a female adult size ofdevice3400, the thickness T30 of thecentral portion3418, as measured from the inner side3410-ito the outer side3410-o, is substantially equal to 12.75 millimeters and the thickness T31 of the bite block is substantially equal to 13.91 millimeters.
• Backplate portion3419 defines alaryngeal side3422 and apharyngeal side3423. Whendevice3400 is assembled, thelaryngeal side3422 ofbackplate portion3419 is attached or fixed to thepharyngeal side3444 ofmask portion3430. Also, whendevice3400 is assembled, the internal passage ofairway tube3410 communicates with theapertures3478 ofsupport3470 so thatdevice3400 defines a sealed airway passage that extends from the proximal end oftube3410 to theanterior side3448 of the bowl shaped opening defined by the inflated cuff.
• As noted above,connector section3411 and integral tube andbackplate section3416 are similar tosection411 and section416 (discussed above, for example, in connection withFIGS. 9A-9G). However,sections3411 and3416 additionally include features that facilitate guiding an endotracheal tube throughdevice3400 and thereby facilitate usingdevice3400 as an intubating laryngeal mask airway device. For example, as shown inFIG. 37D, in thecentral portion3418 of the integral tube andbackplate section3416, the cross section of theairway passage3421 is characterized by a notch, or recess,3424 that extends along the inner surface of convex (or outer) side3410-o. Thisnotch3424, the cross section of which is shaped like a circular arc, preferably extends along the length of thecentral portion3418. It will be appreciated if an endotracheal tube is inserted throughairway tube3410,notch3424 advantageously guides the endotracheal tube along the center of theairway passage3421. Holding the endotracheal tube in the center of the airway passage facilitates aligning the distal tip of the endotracheal tube with the glottic opening and thereby facilitates intubation. It will also be appreciated thatpassage3421 is sized so that if a cylindrical endotracheal tube is inserted into theairway tube3410, the endotracheal tube will not entirely fillpassage3421, and therefore will not obstruct the airway provided bydevice3400. Although the endotracheal tube will fill a cylindrical portion of the passage, defined partially bynotch3424, air will still be able to pass through theairway tube3410 along the left and right sides of the endotracheal tube.
• As shown inFIG. 38D, theairway passage3415 in thedistal portion3413 ofconnector section3411 is characterized by upper andlower notches3426 for guiding an endotracheal tube. The cross section of the internal passage defined bycentral portion3418 preferably smoothly transitions from the one shown inFIG. 37D to one that matches the cross section of the internal passage defined by thedistal portion3413 shown inFIG. 38D, so that there is not an abrupt transition in the shape of the airway passage at the point3411-d. It will be appreciated that in general a variety of shapes for notches or recesses intube3410 may be used for guiding a cylindrical endotracheal tube, however, the considerations for designing the notches are generally as follows. In the relatively straight proximal end ofairway tube3410, it is advantageous to have notches in both the inner and outer sides3410-i,3410-oof the airway tube for holding an inserted endotracheal tube in the center of the airway tube3410 (as shown inFIG. 38D). When an inserted endotracheal tube extends into thecentral portion3418 of integral tube andbackplate section3416, the curve defined by thecentral portion3418 will force the endotracheal tube towards the outer side3410-oofairway tube3410. Accordingly, in the region of the curvedcentral portion3418, it is advantageous to accentuate thenotch3424 that extends along the inner surface of the outer side3410-oof theairway tube3410. It will be appreciated though that notches for guiding an endotracheal tube could extend along the inner surfaces of both the inner and outer sides3410-i,3410-oof thecentral portion3418.
• FIG. 39A shows anendotracheal tube3900 that has been inserted intodevice3400. As shown, the distal tip oftube3900 has been inserted into the proximal end ofairway tube3410 and advanced throughairway tube3410 until the distal tip oftube3900 has extended throughcentral aperture3478 ofsupport3470. From this position, continued advancement ofendotracheal tube3900 will cause its distal tip to enter the patient's glottic opening.
• FIG. 39B shows an anterior view ofendotracheal tube3900 extending throughdevice3400. As shown, the distal tip ofendotracheal tube3900 has extended through thecentral aperture3478 ofsupport3470, thereby pushing thebars4012,4014 that define theapertures3478 laterally, and reducing the size of theapertures3478 on either side of the central aperture.
• FIG. 40A shows another embodiment ofmask portion3430 in which support3470 defines a fenestration, or cut, represented by dashedline4010.Support3470 generally defines twobars4012,4014. Thecentral aperture3478 ofsupport3470 is disposed between thebars4012 and4014. As shown inFIG. 40A, anotheraperture3478 of the support is disposed abovebar4012 and anotheraperture3478 of the support is disposed belowbar4014. Addingfenestration4010 to support3470 effectively detaches the distal end ofbars4012,4014 fromsupport3470 and allows the bars to flap up or down with respect to the rest ofsupport3470. Normally, thebars4012,4014 lie generally coplanar with the rest ofsupport3470. However, whensupport3470 includesfenestration4010, an advancing endotracheal tube can displace thebars4012,4014 in the pharyngeal-to-laryngeal direction with respect to the rest ofsupport3470. When the bars are so displaced, rather than defining threeseparate apertures3478, thesupport3470 can be thought of as defining a single enlarged aperture, and an advancing endotracheal tube can pass through this enlarged aperture.FIG. 40B illustrates anendotracheal tube3900 advancing through asupport3470 which definesfenestration4010. As shown,tube3900 has displaced thebars4012,4014 in the pharyngeal-to-laryngeal direction (i.e., downwards as shown inFIG. 40B) and thetube3900 advances throughsupport3470 without stretching the bars laterally as shown inFIG. 39B. It will be appreciated that the mold used to producemask portion3430 may also include features for definingfenestration4010.
• As noted above, to facilitate insertion of a laryngeal mask airway device into a patient, the deflated device is preferably as thin as possible. With reference toFIG. 16A, the thickest part ofdevice400, when deflated, is shown at T11 and is located at the proximal end of the mask portion. Indevice3400, theairway tube3410 advantageously defines a feature that allows this thickness to be reduced. As shown inFIG. 9E, thelaryngeal side422 of the backplate portion of theairway tube410 is substantially planar. However, as shown inFIG. 37A, thelaryngeal side3422 of the backplate portion of theairway tube3410 is not planar. In particular, the proximal end of thelaryngeal side3422 includes a recessedportion3401 that is angled with respect to the rest of the laryngeal side. As shown inFIG. 34D, during assembly ofdevice3400, when themask portion3430 is initially mated with theairway tube3410, the recessed portion of thelaryngeal side3422 of the backplate portion, causes agap3402 to be defined between the pharyngeal side of the mask portion and the laryngeal side of the backplate portion. This gap is eliminated when fabrication of thedevice3400 is complete (as shown inFIG. 34A) by adhering the proximal end ofpharyngeal side3444 of theplate3440 ofmask portion3430 to the recessedportion3401 of the laryngeal side of the backplate portion of theairway tube3410. It will be appreciated that whendevice3400 is deflated, the presence of the recessedportion3401 allows the thickness of the laryngeal mask airway device to be reduced as compared withdevice400 at the point shown inFIG. 16A at T11.
• When thedevice3400 is in the fully inserted configuration, presence of recessedportion3401 may reduce the pressure applied by the proximal end ofmask portion3430 to the patient's anatomy. However, this reduction in pressure does not appreciably degrade the quality of the seal around the glottic opening provided bydevice3400. The quality of this seal is affected less by pressure between the inflated cuff and the patient's anatomy than by the area of contact between the inflated cuff and the patient's anatomy.Device3400 advantageously increases this area of contact (and thereby improves the quality of the seal), by forming thecuff3460 out of a very thin layer of a very soft material. In exemplary embodiments, the material used to formmask portion3430 is characterized by a durometer of substantially fifty five on the Shore A scale and the thickness of the cuff wall is preferably substantially equal to 0.2 millimeters.Mask portion3430 may be formed from PVC. When thedevice3400 is located in the fully inserted configuration, the intra cuff pressure is preferably between twenty and eighty centimeters of water. Use of this relatively low intra cuff pressure in combination with the very soft and pliable cuff advantageously increases the area of contact between the cuff and the patient's anatomy and thereby provides a high quality seal around the glottic opening.
• The shape of the inflated cuff, and in particular the laryngeal side of the inflated cuff, may also be selectively tailored to increase or decrease the area of contact between the cuff and the patient's anatomy to thereby affect the quality of the seal as well as other parameters. For example,FIGS. 14 and 34C illustrate two different profiles of the laryngeal side of the inflated cuff. A cuff configured as shown inFIG. 14 provides less area of contact with the patient's anatomy than does the cuff shown inFIG. 34C. In particular, the distal tip of the cuff shown inFIG. 34C provides an increased area of contact. The increased area of contact in the cuff shown inFIG. 34C is provided by “rounding” or “softening” the relatively sharp apex of the distal tip of the central aperture of the cuff shown inFIG. 14. It will be appreciated that the profile of the laryngeal side of the cuff shown inFIG. 14 is similar to that of a well known product sold by LMA International SA of Henley, England known as the “Classic”. The distal tip of the cuff shown inFIG. 34C provides an increased area of contact with the patient's anatomy and may thereby increase the quality of seal provided by the device. However, the profile of the laryngeal side of the Classic's cuff (shown generally inFIG. 14), and in particular the relatively sharp apex at the distal end of the cuff's central aperture, may actually be preferred because of other factors. Clinical experience has shown that laryngeal mask airway devices with cuffs having the profile of the Classic may provide improved ventilation characteristics. Accordingly, the profile of the laryngeal side of the Classic's cuff may be the preferred profile for all laryngeal mask airway devices disclosed herein.
• As discussed above in connection withFIG. 20, it can be advantageous to provide the mask portion with arecess2010. Such arecess2010 facilitates placing the backplate portion of the integral tube and backplate section at a desired location on the mask portion during assembly of the laryngeal mask airway device. As indicated by line3510 (shown inFIG. 35D),mask portion3430 may also define a recess for locating the airway tube during assembly. Also, as shown inFIGS. 34A, 34B, and35D,mask portion3430 may also include locatingtabs3520. As shown inFIGS. 37A and 37B, thebackplate portion3419 of integral tube andbackplate section3416 may also definerecesses3530. During assembly ofdevice3400, locatingtabs3520 mate withrecesses3530 and thereby facilitate locating theairway tube3410 at a desired position relative to themask portion3430.
• As discussed above,support3470 advantageously (1) increases the structural integrity ofmask portion3430 without detrimentally affecting the ease of insertion ofdevice3400 and (2) prevents the epiglottis from obstructing the airway provided bydevice3400. Several embodiments ofsupport3470 have been discussed above. However, it will be appreciated that the invention embraces other embodiments of supports that provide similar functions.FIG. 41A shows a top view of anothersupport4170 constructed according to the invention.FIG. 41B shows a side view ofsupport4170 taken in the direction indicated byarrow41B-41B inFIG. 41A.
• As shown,support4170 includes a horseshoe shapedrim4172 and acentral bar4174.Rim4172 extends from aproximal end4176 to distal ends4178.Bar4174 is attached, or fixed, torim4172 at theproximal end4176 and extends along amidline4180 about two thirds of the way towards the distal ends4178.
• FIG. 35A generally depicts a side view of amask portion3430 in which asupport4170 has been installed. When viewed from the side,support4170 will generally follow the dotted lines used inFIG. 35A to denote the location ofsupport3470.Support4170 is preferably adhered to theinner wall3462 of the cuff, as wassupport3470.
• It will be appreciated that likesupport3470,support4170 also resists compression of the mask portion due to forces exerted in the direction of the arrows F shown inFIG. 35B. Also,support4170 does not significantly increase the force required to bend the mask portion around an axis extending in the left-to-right direction as shown inFIG. 17. Also, thecentral bar4174 provides the function of lifting the epiglottis, or preventing the epiglottis from blocking the airway provided by the laryngeal mask airway device. So,support4170 provides similar functions as the above-described embodiment ofsupport3470.
• FIGS. 42 and 43 show other embodiments ofsupports4270,4370 constructed according to the invention. Support4270 (FIG. 42) is similar tosupport4170, however,support4270 does not include a central bar. Support4370 (FIG. 43) is similar tosupport4270 in that it does not define a central bar. However,support4370 is generally elliptical rather than being horse shoe shaped as in the case ofsupports4170 and4270. So, althoughsupports4270,4370 may be used to enhance the structural integrity of the mask portion, and resist collapse of the mask portion in the presence of forces exerted in the direction of the arrows F as shown inFIG. 35B, supports4270,4370 do not assist with preventing the epiglottis from blocking the airway provided by the laryngeal mask airway device. It will be appreciated thatsupport4370 could be modified to include a central bar and thereby also assist with preventing the epiglottis from blocking the airway provided by the laryngeal mask airway device. Supports such as4170 and4270 may be adhered to theinner wall3462 of the cuff of the mask portion. Preferred materials for constructingsupports4170,4270,4370 are PVC. Preferably, the material used to construct these supports is characterized by a durometer of about ninety on the Shore A scale of hardness. These supports may be about 0.7 millimeters thick.
• An advantage to using supports like4170 and4270 is that they may be fabricated from material that is generally stiffer, or harder, than the material used to form the mask portion of the laryngeal mask airway device. In fact, one potential disadvantage to support3470 (as shown in FIGS.35A-E), is that since it is generally made from the same material used to form the rest of the mask portion, thesupport3470 may be softer than desired for sufficiently strengthening the mask portion.FIG. 44 illustrates amask portion3430, which includes asupport3470, being squeezed between two fingers. The pressure applied by the illustrated fingers is in the direction of the arrows F as shown inFIG. 35B, and illustrates how the mask portion may react to pressure applied by anatomical structures of a patient when the mask portion is inserted within a patient. As shown inFIG. 44, the pressure causes the mask portion to partially collapse. More specifically, as a result of the applied pressure, the central aperture defined by the inflated cuff is reduced and theapertures3478 defined by thesupport3470 are also reduced in size. These size reductions, which can occur even if thesupport3470 is thicker than theplate3440 of the mask portion, disadvantageously reduce the size of the airway provided by a laryngeal mask airway device usingmask portion3430.
• One way to overcome these difficulties is to fashion a support using a combination of the plate-like support3470 (as shown, e.g., in FIGS.35A-E) and the ring-like support4370 shown inFIG. 43.FIG. 45A shows a sectional view of amask portion4430 including such asupport4470.FIG. 45A is a sectional view ofmask portion4430 taken in the same direction asFIG. 35E (i.e., in the direction ofline35E-35E as shown inFIG. 35A).FIG. 45B shows an exploded sectional view ofsupport4470 taken from the same perspective asFIG. 45A.FIG. 45C shows a view of a posterior aspect ofmask portion4430.Support4470 includes a plate-like support3470 and a ring-like support4370. Referring toFIG. 45C, horse shoe shaped dashedline4410 represents the places at which plate-like support3470 is detached from theplate3440 ofmask portion4430, and the location of ring-like support4370 is shown by the cross-hatched generally elliptical ring. Plate-like support3470 defines a ring-like notch4414 for receiving ring-like support4370. Ring-like support4370 is preferably adhered to plate-like support3470 so that ring-like support4370 fits into thenotch4414.
• In operation of laryngeal mask airway devices constructed usingmask portion4430, (1) theapertures3478 of plate-like support3470 prevent the epiglottis from blocking the airway provided by the device and (2) the ring-like support4370 tends to prevent theapertures3478 from being closed even when pressure is applied to themask portion4430 in the direction of the arrows F.FIG. 46 shows a view of an anterior aspect of amask portion4430 being squeezed between two fingers. As shown, although the central aperture defined by the inflated cuff is reduced in size by the pressure applied by the fingers, the ring-like support has resisted compression of the plate-like support and thereby resisted compression of theapertures3478.
• As discussed above,support3470 is preferably formed by rotational molding simultaneously with the rest of the mask portion. However, it will be appreciated thatsupport3470 could also be formed of a separate material and incorporated into the laryngeal mask airway device after the mask portion has been formed. For example, a mask portion such as the ones shown inFIGS. 5A-5E could be formed by rotational molding and thesupport3470 could then subsequently be incorporated into the mask portion. Such a support could be formed, for example, from the same material used to form the airway tube of the laryngeal mask airway device.
• FIGS. 47A-47C illustrate another modification that may be made to the airway tube of a laryngeal mask airway device constructed according to the invention useful for guiding an endotracheal tube. The airway tube shown inFIGS. 47A and 47B has been modified to include abar4710. Thebar4710 is disposed in the backplate portion of the airway tube. More specifically, thebar4710 extends in the left-to-right direction across the inner surface of the outer, or convex, side3410-oof the backplate portion of the airway tube.FIG. 47C shows a sectional view ofbar4710 taken in the direction ofline47C-47C as shown inFIG. 47A. As shown inFIG. 47C,bar4710 defines a v-shaped notch4720. The v-shaped notch4720 extends in the proximal-to-distal direction and is positioned for guiding an endotracheal tube. More specifically, the v-shaped notch4720 helps to hold an endotracheal tube in the mid-line during insertion and also guides the distal tip of the endotracheal tube towards the glottic opening.FIG. 47D shows a sectional side view of anendotracheal tube3900 being inserted through a laryngeal mask airway device constructed according to the invention so as to include abar4710.
• FIG. 48A shows a perspective anterior view of thebackplate portion4819 of another embodiment of anairway tube4810 constructed according to the invention.FIG. 48B shows a side view of theairway tube4810 shown inFIG. 48A.Airway tube4810 is similar to airway tubes discussed above (e.g.,airway tube3410 as shown inFIG. 34A). However,airway tube4810 additionally includes two tabs, or ridges,4870 disposed in thebackplate portion4819 of the airway tube.Tabs4870 extend from thelaryngeal side4822 in the pharyngeal-to-laryngeal direction. Referring toFIG. 48B, in an example embodiment, in an adult female size the height H of the tabs4870 (or the amount that the tabs extend away from thelaryngeal side4822 in the pharyngeal-to-laryngeal direction) is substantially equal to 5.8 millimeters.Airway tube4810 may also include a bar, or lateral reinforcement,4870A, which extends in the left to right direction between the twotabs4870.Airway tube4810 is preferably formed by molding a single monolithicpiece including tabs4870 and bar4870A.
• FIG. 48C shows a view of the anterior side of a laryngealmask airway device4800 constructed according to the invention using theairway tube4810 shown inFIGS. 48A and 48B.FIG. 48D shows a side view of thedevice4800.Device4800 is similar to the above-discussed device400 (shown for example inFIGS. 4A-4C) and is made by attaching amask portion4830 to theairway tube4810. As shown inFIG. 48C, thetabs4870 are spaced away from theinner wall4862 of theinflated cuff4860 and thetabs4870 are generally located within the hollow bowl shaped aperture defined by the inflated cuff. Thetabs4870 are preferably shaped to generally match the negative imprint of the pyriform fossae so that, when thedevice4800 is in the fully inserted configuration the tabs rest within spaces defined by the patient's anatomy.
• As discussed above, when a laryngeal mask airway device is in the fully inserted configuration, muscular contraction in the region of the larynx can generate forces in the direction of arrows F as shown inFIG. 35B. These forces bias the inflated cuff towards themidline3431 of the mask portion. If these forces become strong enough, movement of the inflated cuff towards themidline3431 and can reduce the size of, or obstruct, the airway provided by the laryngeal mask airway device. Indevice4800, thetabs4870 on theairway tube4810 advantageously resist movement of theinflated cuff4860 in the direction of the arrows F (FIG. 35B) and thereby act as a counterbalance to these forces. Also, the presence oftabs4870 advantageously does not appreciably increase the difficulty of inserting thedevice4810 into a patient. It will be appreciated thattabs4870 are an alternative to thesupports3470,4170,4270,4370 discussed above, and thattabs4870 may be used alone or in combination with such supports. Also, while the preferred embodiment includes twotabs4870, additional tabs may also be included on the airway tube.
• Since the airway tube is generally made of stiffer material than the mask portion, the airway tube is generally more capable than the mask portion of resisting compressive forces. Thetabs4870, which are part of theairway tube4810, advantageously use the natural stiffness of the airway tube to support the morepliable mask portion4830 so as to maintain an open airway passage even in the presence of compressive forces generated in the patient. Also, since portions of thetabs4870 can rest in the patient's pyriform fossae, the patient's anatomy can assist with holding the tabs in place and resisting compression of the mask portion towards the midline. Finally,bar4870A increases the stiffness of the tube in the left-to-right direction thereby helping to hold thetabs4870 apart.
• The amount by which thetabs4870 extend into the bowl shaped aperture defined by theinflated cuff4860 depends on the thickness of theplate4840 of themask portion4830. In one embodiment in which the thickness ofplate4840 is about 4 millimeters, thetabs4870 extend into the bowl shaped aperture defined by theinflated cuff4860 only by about 2 millimeters. Although thetabs4860 extend into the aperture defined by thecuff4860 by only a small amount, thetabs4860 still advantageously resist compressive forces generated inside the patient and tend to resist obstruction of the airway provided by the laryngeal mask airway device. However, it may be advantageous to make theplate4840 even thinner and have thetabs4870 extend further into the bowl shaped aperture defined by theinflated cuff4860. The height of theinflated mask portion4830 in the region of thetabs4870, shown by the arrow T inFIG. 48D, may affect the ability of thetabs4870 to hold the cuff in an open position. The height of theinflated mask portion4830 may for example be selected so that the distance T, as shown inFIG. 48D, is between about 15 and 18 millimeters when the cuff is not inserted into a patient and when it is inflated to an intra cuff pressure of about 60 cm H₂O.
• As explained above, when a laryngeal mask airway device is in the fully inserted configuration and the patient is reclining on his or her back, the epiglottis sometimes drops down into the aperture defined by the inflated cuff and blocks the airway provided by the device. Indevice4800, if the epiglottis drops down, rather than falling into the passage defined byairway tube4810, the epiglottis is supported bybar4805.Bar4805 is preferably formed as an integral part ofmask portion4830 during the rotational molding process.
• FIGS. 49A and 49B show perspective anterior and side views, respectively, of yet another embodiment of a laryngealmask airway device4900 constructed according to the invention.Device4900 includes anairway tube4810, of the type shown inFIGS. 48A and 48B, and aninflatable cuff4960. In this embodiment, the mask portion of the device is thecuff4960.FIGS. 49C and 49D show side and anterior views, respectively, ofcuff4960.FIG. 49E shows a sectional view ofcuff4960 taken in the direction ofarrow49E-49E as shown inFIG. 49C. Finally,FIG. 49F shows a sectional view ofdevice4900 taken in the direction ofarrow49F-49F as shown inFIG. 49B.
• As shown,cuff4960 is characterized by an elliptical torus shape. The shape is that of a torus, or is toroidal, because the cross section ofcuff4960 at any point is generally circular (e.g., as shown inFIG. 49E). The shape is an elliptical torus because rather than being a perfect ring, or donut shape, the cuff is elongated so that the length of the cuff as measured in the proximal-to-distal direction (or the distance between the cuff'sproximal end4932 and its distal end4934) is greater than the width of the cuff as measured in the left-to-right direction (e.g., as shown generally by the distance W1 as illustrated inFIG. 5E).
• Cuff4960 includes aninflation plug4901 generally located at the cuff'sproximal end4932. In use,plug4901 is coupled to an inflation line (not shown) for controlling inflation and deflation ofcuff4960.
• Unlike the majority of cuffs and mask portions discussed above,cuff4960 is normally not formed by rotational molding. Rather,cuff4960 is normally formed by injection molding or blow molding a plastic such as PVC into the desired elliptical torus shape. The thickness T of the cuff wall, as shown inFIG. 49E, is preferably about 0.5-0.65 millimeters, and the material used to form the cuff is preferably characterized by a durometer of about 55 Shore A. It will be appreciated that many conventional laryngeal mask airway devices include an inflatable cuff similar tocuff4960. It will also be appreciated that the preferred profile of the laryngeal side ofcuff4960 may be different than what is illustrated inFIGS. 49A and 49D. In particular, as discussed above, the preferred profile for the laryngeal side ofcuff4960 may be that of the “Classic” as shown generally inFIG. 14.
• Generally, conventional laryngeal mask airway devices including a cuff similar to that ofcuff4960 also include a thin dome-shaped plastic skin arising from the inner perimeter of the torus. The skin is normally perforated to form three apertures separated by two aperture bars, and the aperture bars support the epiglottis and prevent the epiglottis from blocking the airway provided by the device. Such laryngeal mask airway devices generally also include a relatively stiff backplate which is attached to this dome-shape skin.Device4900 includes neither the skin nor the separate backplate component generally used in those conventional laryngeal mask airway devices. Indevice4900, the airway tube itself in effect forms a backplate by its prolongation adjacent to the pharyngeal surface of the cuff.
• As shown best inFIG. 49F, indevice4900 the laryngeal side of the backplate portion of theairway tube4810 is attached tocuff4960 at thepharyngeal side4944 of the cuff. Attaching theairway tube4810 to thepharyngeal side4944 of the cuff rather than at an equatorial location (i.e., at the midpoint of the cuff as measured in the pharyngeal-to-laryngeal direction) effectively increases the depth of the bowl shaped aperture4942 (as shown inFIG. 49A) defined by the cuff. The arrow A inFIG. 49F illustrates the depth of the bowl shapedaperture4942 indevice4900. The arrow B inFIG. 49G illustrates how much shallower the bowl shaped aperture is in a conventional laryngeal mask airway device in which the backplate is attached to the cuff an equatorial location. Increasing the depth of bowl shapedaperture4942 allows the anatomy of the larynx to extend further into thebowl4942 when thedevice4900 is in the fully inserted configuration and thereby increases the seal provided by the device.
• One potential disadvantage of attaching theairway tube4810 to thepharyngeal side4944 of the cuff rather than at an equatorial location, is that structural support provided to the cuff is reduced and the cuff can become more susceptible to collapse in the presence of forces generated by the patient's anatomy in the direction of the arrows F as shown inFIG. 35B. However, this potential problem is circumvented by the use oftabs4870 in theairway tube4810. As with device4800 (e.g., as shown inFIGS. 48C and 48D), indevice4900 thetabs4870 extend into the bowl shaped aperture defined by thecuff4960 and tend to prevent thecuff4960 from collapsing in the presence of forces in the direction of the arrows F as shown inFIG. 35B. Also as withdevice4800,airway tube4810 may also include a reinforcing strut, or bar,4870A which extends between and connects to bothtabs4870 for further increasing the resistance to collapse. It will be appreciated thatdevice4900 is relatively simple and inexpensive to construct and is another embodiment of a disposable laryngeal mask airway device.
• Since certain changes may be made in the above apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted in an illustrative and not a limiting sense.

Claims (15)

1. A laryngeal mask airway device, comprising:

(A) an inflatable cuff, the cuff defining a central opening at least when inflated;

(B) an airway tube extending from a proximal end to a distal end, the airway tube defining an internal passage, the airway tube defining two or more tabs disposed near the distal end of the airway tube, the cuff being coupled to the airway tube near the distal end of the airway tube, the internal passage extending from the proximal end of the tube to the central opening defined by the cuff, the tabs extending from the airway tube into the central opening defined by the cuff when inflated.

2. A device according toclaim 1, the airway tube including a backplate portion disposed near the distal end of the airway tube, the backplate portion defining a laryngeal side, the tabs extending from the laryngeal side of the airway tube.

3. A device according toclaim 2, the cuff being attached to the laryngeal side of the airway tube.

4. A device according toclaim 1, the cuff defining a pharyngeal side and a laryngeal side, the pharyngeal side being closer than the laryngeal side to a pharynx of a patient when the device is in an inserted location within the patient, the airway tube being attached to the pharyngeal side of the cuff.

5. A device according toclaim 1, the device further including a generally elliptically shaped plate, the cuff being attached to the plate.

6. A device according toclaim 5, the airway tube being attached to the plate.

7. A device according toclaim 1, the cuff being characterized by a circular cross section.

8. A device according toclaim 1, the cuff comprising PVC.

9. A laryngeal mask airway device, comprising:

(A) a mask portion including an inflatable cuff, the mask portion defining a central opening at least when the cuff is inflated;

(B) an airway tube extending from a proximal end to a distal end, the airway tube defining an internal passage, the airway tube defining two or more tabs disposed near the distal end of the airway tube, the mask portion being coupled to the airway tube near the distal end of the airway tube, the internal passage extending from the proximal end of the tube to the central opening defined by the mask portion, the tabs extending from the airway tube into the central opening defined by the mask portion.

10. A device according toclaim 9, the airway tube including a backplate portion disposed near the distal end of the airway tube, the backplate portion defining a laryngeal side, the tabs extending from the laryngeal side of the airway tube.

11. A device according toclaim 10, the mask portion being attached to the laryngeal side of the airway tube.

12. A device according toclaim 9, the mask portion defining a pharyngeal side and a laryngeal side, the pharyngeal side being closer than the laryngeal side to a pharynx of a patient when the device is in an inserted location within the patient, the airway tube being attached to the pharyngeal side of the mask portion.

13. A device according toclaim 12, the mask portion including a generally elliptically shaped plate, the cuff being attached to the plate.

14. A device according toclaim 9, the cuff being characterized by a circular cross section.

15. A device according toclaim 9, the mask portion comprising PVC.

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