US20060287672A1 - Tourniquet cuff with improved pneumatic passageway - Google Patents

Abstract

A tourniquet cuff has minimal flow restrictions within its pneumatic passageway under normal operating conditions, has a substantially reduced likelihood of partial or complete obstructions or interruptions of the pneumatic passageway under foreseeable operating conditions, can indicate exposure of the cuff to external agents that are capable of affecting the integrity of the pneumatic passageway before use, and can be manufactured economically.

Description

FIELD OF THE INVENTION
• This invention pertains to pneumatic tourniquet cuffs commonly used for stopping arterial blood flow into a portion of a surgical patient's limb to facilitate the performance of a surgical procedure, and for facilitating intravenous regional anesthesia.
BACKGROUND OF THE INVENTION
• A typical surgical tourniquet system of the prior art includes a tourniquet cuff for encircling a patient's limb at a desired location and a tourniquet instrument that includes flexible instrument tubing for connecting to the tourniquet cuff. The tourniquet cuff typically includes an inflatable portion, and the inflatable portion of the cuff is typically connected through a cuff port having a port connector to the flexible instrument tubing of the tourniquet instrument, thereby establishing a pneumatic passageway from the tourniquet instrument through the instrument tubing and the cuff port into the inflatable portion of the cuff. In some prior-art systems, the tourniquet instrument includes a pressure transducer to sense the pressure of gas at the instrument end of the pneumatic passageway and to enable the sensed pressure to be displayed for surgical staff. Some prior-art tourniquet instruments include a pressure regulator to increase and decrease the pressure of gas in the pneumatic passageway, and to maintain the pressure in the inflatable portion of the cuff at a pressure above a minimum pressure required to stop arterial blood flow past the cuff during a time period suitably long for the performance of a surgical procedure. Many types of pneumatic surgical tourniquet systems, including tourniquet cuffs and tourniquet instruments, have been described in the prior art, such as those described by McEwen in U.S. Pat. No. 4,469,099, U.S. Pat. No. 4,479,494, U.S. Pat. No. 5,439,477 and by McEwen and Jameson in U.S. Pat. No. 5,556,415 and No. 5,855,589.
• Some tourniquet cuffs of the prior art have only a single port for connection to the tourniquet instrument and thus establish only a single pneumatic passageway between a tourniquet instrument and the inflatable portion of such cuffs. The pressure in the inflatable portion of such single-port tourniquet cuffs must be sensed indirectly from the tourniquet instrument, through the same pneumatic passageway that is used by the tourniquet instrument to increase, decrease and regulate cuff pressure during surgery. The flow resistance of the pneumatic passageway affects the accuracy and speed of regulation of pressure within the inflatable portion of such single-port tourniquet cuffs as well as the accuracy of the indirectly sensed tourniquet cuff pressure.
• Other tourniquet cuffs of the prior art have dual ports to establish two separate pneumatic passageways between the tourniquet instrument and the inflatable portion of the cuff, to achieve increased safety and performance by enabling the tourniquet instrument to provide surgical staff with a more accurate indication of cuff pressure and by enabling the tourniquet instrument to increase the speed and accuracy of cuff pressure regulation. Representative dual-port tourniquet cuffs of the prior are described in U.S. Pat. No. 4,635,635, U.S. Pat. No. 5,454,831, U.S. Pat. No. 5,439,477, U.S. Pat. No. 5,741,295 and U.S. Pat. No. 5,649,954. In one dual-port tourniquet system of the prior art, described in U.S. Pat. No. 4,469,099, the pneumatic pressure regulation elements within the tourniquet instrument communicate with the inflatable portion of the tourniquet cuff through one pneumatic passageway of the tourniquet cuff, and a pressure sensor within the tourniquet instrument communicates pneumatically with the inflatable portion of the cuff through a separate pneumatic passageway of the cuff.
• With both single and dual-port tourniquet systems, the speed and accuracy of pressure regulation and indication are improved if flow restrictions in the pneumatic passageway are minimized. Typical port connectors of the prior art have a male barbed connection portion which fits inside the pneumatic passageway of the port, creating a region of reduced pneumatic flow area and increasing flow resistance between the cuff and the tourniquet instrument.
• One hazard associated with all pneumatic tourniquet cuffs of the prior art is the obstruction of the pneumatic passageway within the cuff. For example, in a single-port tourniquet cuff, a complete obstruction within the pneumatic passageway may allow the actual pressure in the inflatable portion of the cuff to decrease substantially below the desired tourniquet pressure to a level where the cuff may be completely depressurized, or to increase substantially above the desired tourniquet pressure, without any indication to the surgical staff. In effect, the monitoring and regulation of cuff pressure by a prior-art tourniquet instrument stops at the location of the obstruction. As another example, a complete obstruction within a region of the inflatable portion of the cuff may isolate all or part of the inflatable portion and thus may prevent the pressure throughout the entire inflatable portion of the cuff from being sensed and regulated near the desired pressure by the tourniquet instrument. Any isolated region may be hazardous, either by permitting arterial blood to flow into the limb past a region of lower cuff pressure or by requiring surgical staff to set the tourniquet instrument to an unnecessarily high pressure to stop blood flow past the cuff. Also, any complete obstruction of the pneumatic passageway within a tourniquet cuff of the prior art may render ineffective any audio-visual safety alarms of a connected prior-art tourniquet instrument intended to warn of hazardous over-pressurization or under-pressurization of the cuff, such as the safety alarms described by McEwen in U.S. Pat. No. 4,469,099.
• Another hazard associated with tourniquet cuffs of the prior art is partial obstruction of the pneumatic passageway. A partial obstruction of the pneumatic passageway at the port connector, or elsewhere within the port or inflatable portion of a prior-art cuff may increase the pneumatic flow resistance at the partial obstruction, and thus may affect the ability of a connected tourniquet instrument to rapidly and accurately regulate pressure past the partial obstruction and throughout the inflatable portion of the tourniquet cuff. Increased flow resistance from a partial obstruction may also reduce the ability of a connected tourniquet instrument to accurately and rapidly indicate changes of the pressure in the tourniquet cuff to surgical staff. Further, a partial obstruction of the pneumatic passageway within a region of the inflatable portion of the cuff may affect the ability of the tourniquet instrument to uniformly regulate pressure throughout the entire inflatable portion of the cuff.
• In addition to the hazards of complete and partial obstructions that may affect the integrity of the pneumatic passageway, another hazard associated with prior-art cuffs is the interruption of the passageway due to unanticipated detachment of the port connector from the tourniquet instrument, or detachment of the port connector from the port, thus separating the inflatable portion of the tourniquet cuff from the tourniquet instrument. A related hazard is a leak at the port connector that is sufficiently large to prevent a connected tourniquet instrument from maintaining cuff pressure near the desired pressure. Such a large leak may result, for example, from deterioration or deformation of the connector of a single-use disposable tourniquet cuff as a result of reprocessing and reuse of the disposable tourniquet cuff in multiple surgical procedures in a manner neither intended nor anticipated by the manufacturer.
• Many disposable tourniquet cuffs of the prior art are designed to be used in only one single surgical procedure and then discarded. Many such disposable tourniquet cuffs are sterilized at time of manufacture and supplied to users as sterile products, because such cuffs are typically intended to be suitable for use within sterile surgical fields. As a result, the design characteristics of such prior-art cuffs are intended to allow them to be applied and used safely and reliably within a sterile surgical field during one surgical procedure, and to be discarded cost-effectively after that procedure. For example, some disposable tourniquet cuffs of the prior art have a port that includes a very flexible thermoplastic tubing portion having a length sufficient to allow a user to easily bend the port away from the surgical site and position the port connector beyond the sterile surgical field. Although such-long and flexible port tubing facilitates connection of the port to non-sterile instrument tubing away from the sterile surgical field, it may also increase the possibility of partial or complete obstruction of the pneumatic passageway within the port, for example by accidental kinking, bending, or pinching of the tubing. The various materials and components from which such prior-art disposable tourniquet cuffs are assembled are chosen to be sufficiently inexpensive to allow the cuff to be economically discarded after a single use, and also to be capable of sterilization by exposure to a specific sterilizing agent within a specific sterilizing process determined by the manufacturer, with no significant deterioration or change of properties that would impair the safety or performance of the cuffs after such sterilization.
• Efforts have been made to reprocess and reuse tourniquet cuffs of the prior art that were originally supplied by their manufacturers as sterile, single-use products. Reprocessing efforts typically involve saving rather than discarding a disposable tourniquet cuff after surgery, visually examining the cuff to identify any obvious deterioration that might suggest reprocessing is not appropriate, attempting to remove any blood and other surgical debris by washing the cuffs with water combined with any of a variety of detergents or other cleaning liquids, in some cases conducting some functional tests of the cuff, re-packaging the cuff and then sterilizing the re-packaged cuff by exposing it to a sterilization agent within a sterilization process that may be different from that determined by the original manufacturer to be safe and effective. Reprocessing of disposable tourniquet cuffs may be carried out within hospitals or surgery centers or by third-party reprocessors, and the quality and methods of reprocessing are highly variable.
• Reprocessing, cleaning and re-sterilizing of disposable tourniquet cuffs may result in hazards for the surgical patients on whom such cuffs are subsequently used. The hazard arises from the use of any of a variety of chemical or physical agents that are attendant with the reprocessing, cleaning or re-sterilizing processes. For example, exposure of a cuff to liquids during cleaning may allow the liquids to enter the pneumatic passageway of the cuff, where they may remain to partially or complete obstruct the pneumatic passageway of the cuff within the port or inflatable portion. Water remaining within the pneumatic passageway after cleaning may subsequently react chemically with ethylene oxide, a sterilizing agent commonly used in reprocessing, to form ethylene glycol, a sticky substance that may completely or partially block the pneumatic passageway. Exposure of prior-art cuffs to sterilizing agents different than the sterilizing agent employed at the time of manufacture may produce a change and deterioration in the properties of some cuff materials and components, for example due to a chemical reaction or exposure to radiation. Exposure of a prior-art cuff containing flexible thermoplastic materials to an elevated temperature during cleaning or sterilization by known prior-art processes may soften thermoplastic materials and components, increasing the likelihood of hazardous deformation of some components. For example, an elevated temperature during reprocessing may result in substantial deformation of the thermoplastic stiffener included in some prior-art cuffs, thus impairing the application of pressure by such a cuff to an underlying limb upon subsequent use in surgery. Also, an elevated temperature during reprocessing may deform the thermoplastic connectors of some prior-art cuffs, or may weaken the retention force of typical thermoplastic barb-type port connectors, so that such connectors cannot establish or reliably maintain a gas-tight passageway between the tourniquet cuff and tourniquet instrument upon reuse. An elevated temperature associated with cleaning or re-sterilization increases the likelihood that the pneumatic passageway within the cuff may become partially or completely obstructed, as described above, as a result of such reprocessing. Repeated cleaning, re-sterilization and reuse of a disposable tourniquet cuff in multiple surgical procedures may progressively increase the hazard for the surgical patients on whom the cuff is used.
• There is a need for a tourniquet cuff that has minimal flow restrictions within its pneumatic passageway under normal operating conditions, that has a substantially reduced likelihood of partial or complete obstructions or interruptions of the pneumatic passageway under foreseeable operating conditions, that can indicate exposure of the cuff to one or more external agents that are capable of affecting the integrity of the pneumatic passageway before use, and that can be manufactured economically. The present invention addresses this need.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a pictorial representation of the preferred embodiment in a surgical application.
• FIG. 2 shows the cuff portion of the preferred embodiment.
• 3ais a section taken fromFIG. 2, with the uninflated cuff applied to the patient's limb as shown inFIG. 1.
• FIG. 3bis a section taken fromFIG. 2, with the cuff applied to the patient's limb and inflated.
• FIG. 4 is a view looking on the bottom surface of the bladder sealing flange.
• FIG. 5 is a section taken fromFIG. 4.
• FIG. 6ais a section taken fromFIG. 2, showing the preferred embodiment.
• FIG. 7ais a detail view of the areas indicated inFIG. 3aandFIG. 3b, showing the preferred embodiment.
• FIG. 7bis a detail view of the areas indicated inFIG. 3aandFIG. 3b, showing an alternate embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
• FIG. 1 is a pictorial representation of the preferred embodiment in a surgical application, showing thetourniquet cuff10 applied topatient limb12 and pneumatically connectable totourniquet instrument14.Cuff10 includescuff port16, which comprisesbladder sealing flange18,port tubing20, andport connector22. In the preferred embodiment shown,cuff10 is a single port cuff, wherecuff port16 provides a single pneumatic passageway to the inflatable portion ofcuff10. Those skilled in the art will appreciate that the features described in the preferred embodiment may also be applied to tourniquet cuffs having more than one port, such as those described by U.S. Pat. No. 4,469,099, U.S. Pat. No. 4,479,494, and U.S. Pat. No. 5,254,087.Cuff port16 is pneumatically connected to tourniquetinstrument14 viainstrument connector24 andinstrument tubing26. In the preferredembodiment cuff port16 is of sufficient length to allow pneumatic connection betweencuff10 andinstrument14 to be made outside a sterile surgical field.Port connector22 is a locking connector (based on the connector of the tourniquet cuff described by McEwen in U.S. Pat. No. 5,649,954 and similar in some design aspects to connector DSM2202, Colder Products Company, St. Paul, Minn.) which allowscuff port16 to form a releasable pneumatic connection withinstrument connector24.
• As described below,cuff10 is constructed of materials that are appropriate for a single-use sterile disposable tourniquet cuff. To permitcuff10 to be used in a sterile surgical field,cuff10 is sterilized at time of manufacture by exposure to a sterilizing agent within a sterilizing process determined to be safe and effective. To prevent deterioration of the cuff, and to maintain the integrity of the pneumatic passageways withincuff10, a sterilization agent and process that will not harm the materials or components ofcuff10 is selected by the manufacturer. In thepreferred embodiment cuff10 is sterilized by exposure to gamma radiation or electron beam radiation.
• The cost of materials is an important consideration in the manufacture of tourniquet cuffs intended for a single use and then disposal. To minimize the cost of materials and assembly ofcuff10, materials are selected which are not intended to withstand exposure to subsequent sterilization and cleaning processes. The subsequent sterilization or cleaning ofcuff10 by agents and processes commonly used in health care facilities, such as ethylene oxide gas sterilization, hydrogen peroxide gas sterilization, high temperature and pressure steam sterilization, sterilization by other chemical agents, and pasteurization, are all capable of adversely affecting the integrity of the pneumatic passageways ofcuff10. As described further below,cuff10 includes one or more components that act as visual indicators to warn a user thatcuff10 has been subjected to a subsequent sterilization or cleaning process capable of adversely affectingcuff10 and thatcuff10 may no longer be safe to use.
• FIG. 2 shows thecuff10 of the preferred embodiment, which is similar in design and construction to the cuffs described by McEwen in U.S. Pat. No. 5,741,295, U.S. Pat. No. 5,649,954, U.S. Pat. No. 5,484,831 and by Robinette-Lehman in U.S. Pat. No. 4,635,635. In the preferred embodiment shown,cuff10 is rectangular with a length sufficient to encircle an adult arm as shown inFIG. 1. Those skilled in the art will appreciate that the features described in the preferred embodiment may also be incorporated in cuffs of various sizes and shapes, such as those described by McEwen in U.S. Pat. No. 5,649,954. In addition tocuff port16,cuff10 comprisestie ribbon28,loop material30, edge trim32, sewn joint34, andhook material36. In use,cuff10 is wrapped snugly around the limb12 (seeFIG. 1) and secured circumferentially around the limb when the user engageshook material36 toloop material30.Tie ribbon28 is a soft fabric ribbon material (Grosgrain ⅝″ wide, Dynatex Textiles Inc., Toronto, Ontario, Canada) and allows the user to pullcuff10 snug around the limb. Whencuff10 is in position and secured circumferentially around the limb, the user ties tieribbon28 as shown inFIG. 1 to help prevent the cuff from sliding proximally or distally on the limb when inflated. Edge trim32 is made of similar material to tieribbon28 and helps prevent chafing of the patient's limb by the edges ofcuff10.
• FIG. 3ais a section taken fromFIG. 2, however withcuff10 applied to the limb12 (as shown inFIG. 1) andcuff10 uninflated.Top layer38 andbottom layer40 are made of woven nylon cloth coated with thermoplastic material (for example, 200 Denier nylon cloth coated in thermoplastic polyurethane 0.006″ thick) on the surfaces that facemiddle layer42.Middle layer42 is made of thermoplastic sheet material (for example, 0.020″ thick polyurethane).Stiffener44 is made of plastic sheet cut to a rectangular shape fitting within the perimeter ofcuff10. Thestiffener44 has greater stiffness thanlayers38,40, and42 but is flexible enough to be wrapped around the limb (for example 0.020″ thick polyethylene sheet).Top layer38,middle layer42, andbottom layer40 are joined around a continuous perimeter within the perimeter ofcuff10 atbladder seal46, thereby forminginflatable bladder48 betweenmiddle layer42 andbottom layer40 and enclosingthermoplastic stiffener44 betweentop layer38 andmiddle layer42.Bladder48 therefore has a width at the port location as shown inFIG. 3a, a typical value being 3.5 inches, and a length extending along the length of the cuff (seeFIG. 2) and sufficient to encircle the limb. When secured circumferentially around the limb as shown inFIG. 1,stiffener44 helps direct the expansion ofinflatable bladder48 radially inwards towards the limb upon inflation of the cuff. The stiffener thus provides uniformly distributed pressure ontolimb12.
• Bladder seal46 is formed by a heat and pressure joining process, typically radio-frequency welding using a selected sealing die. The heat of the joining process is selected to temporarily melt a portion of the thermoplastic materials inlayers38,40, and42, causing them to fuse together in the area ofbladder seal46. The pressure of the joining process in combination with the shape of the sealing die is selected to squeeze a predetermined portion of the melted thermoplastic materials inlayers38,40, and42 out of the area ofbladder seal46, forming acontinuous bead50 along the perimeter ofinflatable bladder48. When the joining process is complete,bead50 solidifies back to the original rigidity of the thermoplastic materials inlayers38,40, and42 and has thickness51 (shown inFIG. 3bonly for clarity).Thickness51 is proportional to the selected amount of thermoplastic material squeezed out during the formation ofbladder seal46, and is selected to be large enough to form and maintain bladderpneumatic passageway52 whenbottom layer40 is compressed againstmiddle layer42 during certain conditions of use, which are described in more detail below.
• Cuff port16 ofcuff10 comprisesport connector22,port tubing20, andbladder sealing flange18, which are permanently joined together with pneumatically sealed joints to form port tubingpneumatic passageway54 and port connector pneumatic passageway55 (seeFIG. 7a) which form a continuous pneumatic passageway extending fromdistal port end53 toinflatable bladder48.Bladder sealing flange18 has flangetop surface56 which is permanently joined tomiddle layer42 by a heat sealing process similar to that used to form bladder seal46 (as described above).Bladder sealing flange18 also hasbottom surface58.Port tubing20 has a length betweenbladder end59 andport connector22, which is at minimum greater than the bladder width at the port location, and preferably30 inches, which is sufficient to extend outside the sterile surgical field.Bladder sealing flange18 forms a portion ofpneumatic passageway54 extending from porttubing bladder end59 and formed to enterinflatable bladder48 in a direction normal totop surface56 andbottom surface58 ofbladder sealing flange18, and thereby normal to the area ofmiddle layer42 aroundbladder sealing flange18.
• FIG. 3bis a section taken fromFIG. 2, however withcuff10 applied to the limb12 (as shown inFIG. 1) andcuff10 inflated.Inflatable bladder48 is shown expanded radially inwards towards the limb.
• FIG. 4 is a view looking onbottom surface58 ofbladder sealing flange18.Bladder sealing flange18 is made of thermoplastic polyurethane by injection molding (in a similar manner to existing sealing flanges such as 167ACU-BK, Halkey Roberts Corp., St. Petersburg, Fla. which are currently used in tourniquet cuffs). A plurality ofchannels60 are formed insurface58 extending from the outer perimeter offlange18 to portpneumatic passageway54.
• FIG. 5 is a section taken fromFIG. 4, showing atypical channel60 formed in the area between flangebottom surface58 and flangetop surface56. Becausebladder sealing flange18 must be heat sealed tomiddle layer42,channels60 may be formed in to surface58 by correspondingly shaped ridges on the sealing die and therefore are formed during the heat sealing process ofbladder sealing flange18 tomiddle layer42 with no additional per item cost compared to the typical prior-art tourniquet cuffs.
• Referring toFIGS. 1, 3a,4, and5, whenport connector22 is connected toinstrument14, a pneumatic passageway is established frominstrument14 through port pneumatic passageway54 (formed by the openings inport connector22,port tubing20, and bladder sealing flange18),channels60 in bladder sealingflange bottom surface58 intoinflatable bladder48.Bead50 acts to hold open thebladder48 near thebladder seal46 thereby establishing abladder pneumatic passageway52 around the perimeter ofinflatable bladder48, allowing pneumatic communication throughout the bladder.
• Ifbladder sealing flange18 is compressed against limb12 (for example if the flange area of the cuff is lying between the limb and the operating room table or bolster on which the limb is resting, orcuff10 is applied tolimb12 too tightly),bottom layer40 may be pressed againstflange bottom surface58 as shown inFIG. 3a. On bladder sealing flanges typically used in tourniquet cuffs of the prior art (for example see 167ACU-BK, Halkey Roberts Corp., St. Petersburg, Fla.),surface58 is flat and smooth. Using prior-art flanges in the condition shown inFIG. 3a, pneumatic communication betweeninflatable bladder48 and portpneumatic passageway54 is closed off or restricted. In the current invention, however,channels60 form a plurality of pneumatic passageways betweeninflatable bladder48 and portpneumatic passageway54 in the area between flangebottom surface58 and flangetop surface56, which remain open whenbottom layer40 is compressed againstflange bottom surface58.
• Furthermore, if any area of the cuff containinginflatable bladder48 is compressed against the limb,bottom layer40 may be pressed againstmiddle layer42 in some areas (as shown inFIG. 3a) which may restrict or close pneumatic communication between different regions ofinflatable bladder48.Bead50 separatesmiddle layer42 andbottom layer40, thereby establishing bladderpneumatic passageway52 extending around the entire perimeter ofinflatable bladder48 as noted above. The size ofbead50 is selected such that bladderpneumatic passageway52 is maintained under the compression forces betweenbottom layer40 andmiddle layer42 expected in surgical use, thereby maintaining pneumatic communication among all regions ofbladder48.
• In addition to the conditions described above which may occur during the normal use ofcuff10, exposure ofcuff10 to an elevated temperature or pressure, or exposure ofcuff10 to certain chemicals, or a combination of these conditions may occur during storage, shipping, or subsequent cleaning and sterilization processes and may causebottom layer40 to adhere to flangebottom surface58 or areas ofmiddle layer42 by softening the thermoplastic materials. If the materials adhere, pneumatic passageways will nonetheless be maintained bybead50 andchannels60.
• FIG. 6ais a section taken fromFIG. 2, showing the cross-sectional profile ofport tubing20 ofcuff port16, extending from bladder end59 (seeFIGS. 3aand3b) to port tubing end61 (seeFIG. 7a).Port tubing20 is formed by an extrusion process and is made of a blend of thermoplastic polyurethane and sterilization indicator formulated to change color when exposed to certain agents that, as noted above, may have a deleterious effect on the integrity of the pneumatic passageway. In this embodiment, the sterilization indicator does not react to change color during the initial sterilization ofcuff10 by gamma or electron beam radiation at time of manufacture. In the preferred embodiment, the thermoplastic material is formulated to undergo a distinct and permanent color change upon exposure to predetermined minimum levels of one or more selected sterilizing agents different than the agent employed at time of manufacture and typical of those commonly used within health care facilities and by reprocessors. Ethylene oxide gas is one such secondary sterilizing agent that may be used in a reprocessing sterilization process. Other agents are hydrogen peroxide gas, high temperature steam, and other chemical sterilizing agents. This color change occurs over the length ofport tubing20 and is visually perceptible by the user to indicate thatcuff10 has undergone a subsequent sterilization capable of affecting the pneumatic communication described above and shown inFIG. 3a. To enhance the appearance of the color change that takes place withinport tubing20 upon exposure to a subsequent sterilizing process, a portion ofport tubing20 may be marked with a substance that does not change color upon exposure to the sterilization process. For example,port tubing20 may be formed from a thermoplastic material that normally has a clear color and changes to a brown color upon exposure to the ethylene oxide sterilization process.Port tubing20 may also be marked with a white stripe which runs the length ofport tubing20. Whenport tubing20 is exposed to the sterilization process the printed white stripe provides visual contrast to the underlying, brown-colored tubing.
• In the preferred embodiment the secondary sterilization indicator described above is formulated from a color-forming compound pre-selected to react with a predetermined minimum level of ethylene oxide in a secondary sterilization process. Color-forming compounds such as 4-(hydrazinocarbonyl) pyridine, 4-nitrobenzylpyridine, or other pyridines that react with ethylene oxide may be used alone or in combination to produce a non-reversible color change reaction upon exposure to ethylene oxide gas. The color-forming compound may also include catalysts that further promote the color change reaction. To increase utility, the secondary sterilization indicator of the preferred embodiment may be mixed with additional color-forming compounds known in the art that react to change color in the presence of hydrogen peroxide gas or high temperature steam. The sterilization indicator may also include other non-reactive pigments pre-selected to enhance the visibility of the color-forming compound in its reacted state, thereby making a color change more visually perceptible by a user.
• To further indicate to a user thatcuff10 has been exposed to a second sterilization agent within a sterilization process different than that used at time of manufacture, the secondary sterilization indicator may be carried on another component ofcuff10, such as a label attached tocuff10, or the surface ofport tubing20 or the surface oftie ribbon28. For example,tie ribbon28 may be selected to be initially white in color and upon the subsequent sterilization ofcuff10 by ethylene oxide sterilization change color to brown.
• To indicate exposure ofcuff10 to a physical agent such as heat at a temperature that is capable of deforming, obstructing or otherwise adversely affecting the integrity ofpneumatic passageways54 or55 or portions ofinflatable bladder48, an irreversible thermochromic indicator compound is carried on a selected surface ofcuff10, for example a surface ofport tubing20. Thermochromic indicators are known in the art and may be formulated to react by irreversibly changing color at a predetermined temperature to indicate that exposure to the predetermined temperature has taken place. The preferred thermochromic indicator is unaffected by the initial sterilization ofcuff10 at time of manufacture. By carrying the preferred thermochromic indicator on a selected surface ofcuff10, an indication perceptible by a user ofcuff10 is produced whencuff10 has been exposed to a potentially damaging and hazardous temperature. Alternately, exposure ofcuff10 to an elevated temperature that is potentially damaging and hazardous may be indicated by a temperature-indicating compound that liquefies at the predetermined temperature. For example, a temperature-indicating compound (Tempilaq G TL0175, Tempil Inc., South Plainfield, N.J., which is applied like paint, re-liquifies upon reaching the predetermined temperature, then re-solidifies upon cooling below the predetermined temperature) may be carried onport tubing20.Port tubing20 of the preferred embodiment is made of a transparent thermoplastic polyurethane having a clear color and thus a distinct pattern of temperature-indicating compound having a different color may be applied or printed in a particular pattern alonginner surface64 so that, ifinner surface64 reaches or exceeds the predetermined temperature, the compound reacts by liquefying and, causing the pattern to spread out and change to a colored smear. This distinct change of the printed pattern carried oninner surface64 provides a visual indication perceptible by auser cuff10 has been exposed to an elevated temperature at least equal to the predetermined temperature and thatcuff10 thus may be unsafe to use.
• A water-indicating compound (such as a water-soluble ink) may be formed into a printed pattern carried on a selected surface ofcuff10, as described in the preceding paragraph for an elevated temperature-indicating compound. Introduction of water or other liquid agents intopneumatic passageway54 during any reprocessing could partially or completely obstructpneumatic passageway54. Moreover, the water could indirectly obstruct the passageway by reacting chemically with secondary sterilizing agents such as ethylene oxide. A water-soluble pattern of colored ink carried oninner surface64 ofport tubing20 would react to and indicate the introduction of water intopneumatic passageway54 by changing the pattern, and the change would be readily perceptible by a user.
• It will be appreciated that the indicating compounds described above for water, temperature and secondary sterilizing agents may be used alone or in combination, and carried on selected surfaces ofcuff10 or combined when forming components ofcuff10, to indicate to a user thatcuff10 has been subjected to a subsequent sterilization or cleaning process capable of adversely affectingcuff10 and thatcuff10 may no longer be safe to use.
• Referring again to the cross-sectional profile ofport tubing20 shown inFIG. 6a,port tubing20 hasouter surface62 having a circular cross-sectional shape,inner surface64, andridge66.Outer surface62,inner surface64, andridge66 together formwall68 having a non-uniform thickness, andpneumatic passageway54 which has a non-circular cross-sectional shape.Ridge66 protrudes intopneumatic passageway54 and thereby prevents complete occlusion ofpneumatic passageway54 ifport tubing20 is kinked or flattened. In contrast, existing flexible tubing typically used in tourniquet cuffs has inner and outer surfaces of a circular cross-sectional shape, and do not haveridge66. Due to the stiffening properties of the cross-sectional shape shown inFIG. 6athe cross-sectional area ofwall68 is selected to be similar or less than that of existing flexible tubing currently used in disposable tourniquet cuffs, resulting in an equivalent volume of material per unit length, and the constant cross-sectional shape ofport tubing20 allows manufacture by well proven and cost -effective extrusion methods as used for prior-art tubing, resulting in a cost of manufacture ofport tubing20 that is similar to that of the prior-art tubing.
• FIG. 6bis a section taken fromFIG. 2, showing an alternate cross-sectional profile ofport tubing20 ofcuff port16, having a plurality ofridges66 providing increased resistance to occlusion compared to the cross section shown inFIG. 6a. Those skilled in the art will recognize that the size, shape, and number ofridges66 may be selected to provide an anti-occlusive effect for a particular overall size and stiffness ofport tubing20, and selected to minimize the required cross-sectional area ofwall68 and thereby minimize the cost ofport tubing20.
• FIG. 7ais a detail view taken fromFIGS. 3aand3b, showing the preferred embodiment.Port connector22 is formed by an injection molding process, like the process used to form connectors of type DSM2202 (Colder Products Company, St. Paul, Minn.) that are used in commercial tourniquet cuffs derived from the cuff described by McEwen in U.S. Pat. No. 5,649,954. However, unlike these prior-art connectors,port connector22 is made of a blend of thermoplastic polyethylene and sterilization indicator formulated to change color when exposed to the predetermined conditions described above forport tubing20. The polyethylene component of the material used to makeport connector22 is selected to have similar stiffness, strength, sliding, and sealing properties to the polyethylene material of the connectors in the McEwen '954 cuff and of the DSM2202 connectors in related commercial cuffs of the prior art, thereby ensuring compatibility with female connectors intended for use with the DSM2202 connector. The secondary sterilization indicator of unauthorized reprocessing is as described above forport tubing20. Alternatively or in addition,port connector22 may carry a temperature indicating compound on one or more selected surfaces as described above forport tubing20.Port connector22 may also carry a water-indicating compound on one or more selected surfaces, as described above forport tubing20.
• A change in the color ofport connector22 from a first predetermined color to a second predetermined color as described above provides an indication that is visually perceptible by a user ofcuff10. Further, the above-described change of color ofport connector22 can be remotely and automatically detected by connectedtourniquet instrument14, for example by incorporating the apparatus described by McEwen in U.S. Pat. No. 6,682,547 and U.S. Patent Application No. 20030167070, both of which documents are hereby incorporated by reference. In this regard, the instrument is provided with a light emitter and light detector (such as a photodiode) arranged so that changes in the color of the port connector (or the color change of other part of the cuff that is in the optic path between the emitter and detector) will corresponding alter the light intensity reaching the detector so that the output signal associated with the detector is indicative of the color change, hence automatically indicating the exposure to the agent that caused the color change.
• Port connector22 includes actuatingflange70,annular groove72, anddeformable ring74 as described by McEwen in U.S. Pat. No.5,649,954 and similar in design to the existing DSM2202 connector, thereby makingport connector22 compatible with female connectors intended for use with the DSM2202 connector. However while the prior-art connectors typically have a male barbed portion that fits inside flexible plastic tubing having a circular inner cross section,port connector22 is adapted for easy assembly to porttubing20 that hasinner surface64 of a non-circular cross section (seeFIGS. 6aand6b).Port connector22 is joined toport tubing20 by sliding femalecylindrical flange76 overouter surface62 and bonding at the mating surface. This arrangement forms port connectorpneumatic passageway55 extending fromport tubing end61 todistal port end53 and provides greater pneumatic flow area compared to the existing DSM2202 connector by eliminating the male barbed portion of the connector insidepneumatic passageway54 and allowing the cross-sectional area of the port connectorpneumatic passageway55 to be equal to or greater than that port tubingpneumatic passageway54 ofport tubing20. This greater flow area improves the speed of inflation and deflation ofcuff10 and makespneumatic passageways54 and55 less likely to become occluded by kinking, compression, or debris. Furthermore bondingport connector22 toport tubing20 onouter surface62 increases bond area compared to the typical arrangement seen in the prior art (inserting a male connection portion of the port connector into the inner surface of the flexible plastic tubing), which improves the strength and pneumatic sealing properties of the bond. The volume of material in femalecylindrical flange76 is similar to that of the male barbed portion of the existing DSM2202 connector, and the mold required to form femalecylindrical flange76 is simpler, so the cost of manufacture ofport connector22 is similar to or less than that of the prior-art connector.
• FIG. 7bis a detail view taken fromFIGS. 3aand3b, showing an alternate embodiment in which port connector22 (seeFIG. 7a) is integrated withport tubing20 to reduce manufacturing cost. In this embodiment, the end ofport tubing20 is formed to create actuatingflange70,annular groove72, anddeformable ring74. The thermoplastic material is as described above forport connector22 and undergoes a distinct color change upon exposure to predetermined conditions. This alternate embodiment eliminates the assembly and bonding ofport connector22 toport tubing20 as described in the preferred embodiment.

Claims (21)

1. A tourniquet cuff comprising:

an inflatable bladder having a width dimension at a port location and a length dimension sufficient for encircling a patient's limb at a desired location;

a port attached to the bladder at the port location and releasably connectable to a tourniquet instrument, wherein the port includes a pneumatic passageway that enables the inflatable bladder to communicate pneumatically with the connected tourniquet instrument; and

an indicator applied to the cuff and reactive to an agent that is capable of affecting the integrity of the pneumatic passageway and for producing an indication if the agent reaches a predetermined level.

2. The apparatus as described inclaim 1 wherein the agent to which the indicator reacts is a predetermined sterilizing agent and wherein the indication is a change of color.

3. The apparatus as described inclaim 1 wherein the indication is remotely detectable by a tourniquet instrument.

4. The apparatus as described inclaim 1 wherein the indicator is carried on the port.

5. The apparatus as described inclaim 1 wherein the port is formed from a blend of thermoplastic material and the indicator.

6. The apparatus as described inclaim 1 wherein the indication is perceptible by a user.

7. The apparatus as described inclaim 1 wherein the agent to which the indicator reacts is water.

8. The apparatus as described inclaim 1 wherein the agent to which the indicator reacts is exposure to a temperature above a predetermined level.

9. The apparatus as described inclaim 1 wherein the agent is capable of affecting the integrity of the inflatable bladder.

10. A tourniquet cuff having an improved pneumatic passageway, comprising:

an inflatable bladder having a bladder length sufficient for encircling a patient's limb at a desired location,

port tubing communicating pneumatically with the inflatable bladder and having a port tubing end, a port tubing length and a substantially cylindrical outer surface that contains a pneumatic passageway of predetermined cross-sectional area along the port tubing length and through the port tubing-end, and

a port connector configured for establishing a pneumatic connection between the port tubing and a tourniquet instrument, wherein the pneumatic connection established by the port connector has a cross-sectional area that is not less than the predetermined cross-sectional area of the pneumatic passageway.

11. The apparatus as described inclaim 10 wherein the port connector receives the port tubing end and wherein the connector is attached to the outer surface of the port tubing near the port tubing end by an attachment means having a strength sufficient to maintain the attachment to the outer surface in the presence of a force along the port tubing length in a direction away from the connector that is greater than a maximum force anticipated during surgical use.

12. The apparatus as described inclaim 10 wherein the port connector is a predetermined shape formed on the outer surface of the port tubing near the port tubing end and wherein the shape is adapted to be received by a tourniquet instrument connector of the tourniquet instrument to establish the pneumatic connection.

13. A tourniquet cuff having an improved pneumatic passageway, comprising:

an inflatable bladder having a bladder width and having a bladder length sufficient for encircling a patient's limb at a desired location,

a port communicating pneumatically with the bladder and including port tubing, wherein the port tubing is formed of thermoplastic material having a substantially cylindrical outer surface, a port tubing length greater than the bladder width, a bladder end and a port tubing end, wherein the port tubing contains a pneumatic passageway between the bladder end and the port tubing end, and wherein the passageway has a predetermined non-circular cross-sectional shape.

14. The apparatus as described inclaim 13 wherein the port tubing includes a ridge adjacent to the pneumatic passageway that extends from the bladder end to the port tubing end.

15. The apparatus as described inclaim 13 wherein the port tubing includes a plurality of ridges adjacent to the pneumatic passageway that extend from the bladder end to the port tubing end.

16. The apparatus as described inclaim 13 and including a port connector that is non-releasably bonded to the outer surface of the port tubing near the port tubing end and wherein the connector is adapted for connection to a tourniquet instrument to establish a gas-tight passageway between the bladder and the instrument.

17. A tourniquet cuff having an improved pneumatic passageway, comprising:

a first layer having a width dimension, a length dimension and a sealing surface,

a second layer having a width dimension, a length dimension and a sealing surface positioned against the sealing surface of the first layer and sealed around a perimeter to form an inflatable bladder within the perimeter,

a port having a bladder sealing flange sealed to the first layer sealing surface around the flange to establish a pneumatic passageway from a distal port end outside the first layer through the port and into the bladder along a channel formed in the flange.

18. The apparatus as described inclaim 17 and including a plurality of parallel channels formed in the flange to establish a plurality of pneumatic passageways through the flange.

19. The apparatus as described inclaim 17 wherein the port further contains a normal channel of predetermined cross-sectional area extending through the flange and into the bladder in a direction normal to the first layer and wherein the pneumatic passageway into the bladder further includes the normal channel when the second layer is not in contact with the flange.

20. A tourniquet cuff having an improved pneumatic passageway, comprising:

a first layer of flexible thermoplastic material having a first layer sealing surface,

a second layer of flexible thermoplastic material having a second layer sealing surface facing the first layer sealing surface,

a perimeter seal establishing a gas-tight seal between the first layer sealing surface and the second layer sealing surface around a predetermined perimeter to form an inflatable bladder within the perimeter seal, wherein the perimeter seal includes a bead protruding into the inflatable bladder and having a bead thickness greater than a predetermined bead thickness to separate the first sealing surface from the second sealing surface, thereby establishing a bladder pneumatic passageway near the bead.

21. The apparatus as described inclaim 20 and including a port having a bladder sealing flange of predetermined thickness and predetermined circumference sealed to the first layer sealing surface around the circumference and passing through the first layer to establish a port passageway from a distal port end outside the first layer through the port and into the bladder near the edge of the bladder sealing flange along a channel formed in the port seal flange.

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