US20100049014A1 - Sensor Inserter Assembly - Google Patents

Abstract

An analyte monitor includes a sensor, a sensor control unit, and a display unit. The sensor control unit typically has a housing adapted for placement on skin and is adapted to receive a portion of an electrochemical sensor. The sensor control unit also includes two or more conductive contacts disposed on the housing and configured for coupling to two or more contact pads on the sensor. A transmitter is disposed in the housing and coupled to the plurality of conductive contacts for transmitting data obtained using the sensor. The display unit has a receiver for receiving data transmitted by the transmitter of the sensor control unit and a display coupled to the receiver for displaying an indication of a level of an analyte, such as blood glucose. An inserter having a retractable introducer is provided for subcutaneously implanting the sensor in a predictable and reliable fashion.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• This non-provisional application is related to and claims priority based on U.S. Provisional Application No. 60/424,099, entitled “Sensor Inserter Device and Methods of Use,” filed on Nov. 5, 2002, which is incorporated herein in its entirety by this reference.
FIELD OF THE INVENTION
• The present invention is, in general, directed to devices and methods for the in vivo monitoring of an analyte, such as glucose or lactate, using a sensor to provide information to a patient about the level of the analyte. More particularly, the present invention relates to devices and methods for inserting a subcutaneously implantable electrochemical sensor in a patient for such monitoring.
BACKGROUND OF THE INVENTION
• The monitoring of the level of glucose or other analytes, such as lactate or oxygen, in certain individuals is vitally important to their health. High or low levels of glucose or other analytes may have detrimental effects. The monitoring of glucose is particularly important to individuals with diabetes, as they must determine when insulin is needed to reduce glucose levels in their bodies or when additional glucose is needed to raise the level of glucose in their bodies.
• A conventional technique used by many diabetics for personally monitoring their blood glucose level includes the periodic drawing of blood, the application of that blood to a test strip, and the determination of the blood glucose level using colorimetric, electrochemical, or photometric detection. This technique does not permit continuous or automatic monitoring of glucose levels in the body, but typically must be performed manually on a periodic basis. Unfortunately, the consistency with which the level of glucose is checked varies widely among individuals. Many diabetics find the periodic testing inconvenient and they sometimes forget to test their glucose level or do not have time for a proper test. In addition, some individuals wish to avoid the pain associated with the test. These situations may result in hyperglycemic or hypoglycemic episodes. An in vivo glucose sensor that continuously or automatically monitors the individual's glucose level would enable individuals to more easily monitor their glucose, or other analyte, levels.
• A variety of devices have been developed for continuous or automatic monitoring of analytes, such as glucose, in the blood stream or interstitial fluid. A number of these devices use electrochemical sensors which are directly implanted into a blood vessel or in the subcutaneous tissue of a patient. However, these devices are often difficult to reproducibly and inexpensively manufacture in large numbers. In addition, these devices are typically large, bulky, and/or inflexible, and many can not be used effectively outside of a controlled medical facility, such as a hospital or a doctor's office, unless the patient is restricted in his activities.
• Some devices include a sensor guide which rests on or near the skin of the patient and may be attached to the patient to hold the sensor in place. These sensor guides are typically bulky and do not allow for freedom of movement. In addition, the sensor guides or the sensors include cables or wires for connecting the sensor to other equipment to direct the signals from the sensors to an analyzer. The size of the sensor guides and presence of cables and wires hinders the convenient use of these devices for everyday applications. The patient's comfort and the range of activities that can be performed while the sensor is implanted are important considerations in designing extended-use sensors for continuous or automatic in vivo monitoring of the level of an analyte, such as glucose. There is a need for a small, comfortable device which can continuously monitor the level of an analyte, such as glucose, while still permitting the patient to engage in normal activities. Continuous and/or automatic monitoring of the analyte can provide a warning to the patient when the level of the analyte is at or near a threshold level. For example, if glucose is the analyte, then the monitoring device might be configured to warn the patient of current or impending hyperglycemia or hypoglycemia. The patient can then take appropriate actions.
SUMMARY OF THE INVENTION
• Generally, the present invention relates to methods and devices for the continuous and/or automatic in vivo monitoring of the level of an analyte using a subcutaneously implantable sensor. Many of these devices are small and comfortable when used, thereby allowing a wide range of activities. One embodiment includes a sensor control unit having a housing adapted for placement on skin. The housing is also adapted to receive a portion of an electrochemical sensor. The sensor control unit includes two or more conductive contacts disposed on the housing and configured for coupling to two or more contact pads on the sensor. A transmitter is disposed in the housing and coupled to the plurality of conductive contacts for transmitting data obtained using the sensor. The sensor control unit may also include a variety of optional components, such as, for example, adhesive for adhering to the skin, a mounting unit, a receiver, a processing circuit, a power supply (e.g., a battery), an alarm system, a data storage unit, a watchdog circuit, and a measurement circuit. The sensor itself has at least one working electrode and at least one contact pad coupled to the working electrode or electrodes. The sensor may also include optional components, such as, for example, a counter electrode, a counter/reference electrode, a reference electrode, and a temperature probe. The analyte monitoring system also includes a display unit that has a receiver for receiving data from the sensor control unit and a display coupled to the receiver for displaying an indication of the level of an analyte. The display unit may optionally include a variety of components, such as, for example, a transmitter, an analyzer, a data storage unit, a watchdog circuit, an input device, a power supply, a clock, a lamp, a pager, a telephone interface, a computer interface, an alarm or alarm system, a radio, and a calibration unit. In addition, the analyte monitoring system or a component of the analyte monitoring system may optionally include a processor capable of determining a drug or treatment protocol and/or a drug delivery system.
• According to one aspect of the invention, an insertion kit is disclosed for inserting an electrochemical sensor into a patient. The insertion kit includes an introducer. A portion of the introducer has a sharp, rigid, planer structure adapted to support the sensor during insertion of the electrochemical sensor. The insertion kit also includes an insertion gun having a port configured to accept the electrochemical sensor and the introducer. The insertion gun has a driving mechanism for driving the introducer and electrochemical sensor into the patient, and a retraction mechanism for removing the introducer while leaving the sensor within the patient.
• According to another aspect of the invention, a method of using an electrochemical sensor is disclosed. A mounting unit is adhered to skin of a patient. An insertion gun is aligned with a port on the mounting unit. The electrochemical sensor is disposed within the insertion gun and then the electrochemical sensor is inserted into the skin of the patient using the insertion gun. The insertion gun is removed and a housing of the sensor control unit is mounted on the mounting base. A plurality of conductive contacts disposed on the housing is coupled to a plurality of contact pads disposed on the electrochemical sensor to prepare the sensor for use.
• The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and the detailed description which follow more particularly exemplify these embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
• The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:
• FIG. 1 is a block diagram of one embodiment of a subcutaneous analyte monitor using a subcutaneously implantable analyte sensor, according to the invention.
• FIG. 2 is a top view of one embodiment of an analyte sensor, according to the invention.
• FIG. 3 is an expanded side view of one embodiment of a sensor and an introducer, according to the invention.
• FIGS. 4A,4B,4C are cross-sectional views of three embodiments of the introducer ofFIG. 3.
• FIG. 5 is a cross-sectional view of one embodiment of a on-skin sensor control unit, according to the invention.
• FIG. 6 is a top view of a base of the on-skin sensor control unit ofFIG. 5.
• FIG. 7 is a bottom view of a cover of the on-skin sensor control unit ofFIG. 5.
• FIG. 8 is a perspective view of the on-skin sensor control unit ofFIG. 5 on the skin of a patient.
• FIG. 9 is a perspective view of the internal structure of an insertion gun, according to the invention.
• FIG. 10A is a top view of one embodiment of an on-skin sensor control unit, according to the invention.
• FIG. 10B is a top view of one embodiment of a mounting unit of the on-skin sensor control unit ofFIG. 10A.
• FIG. 11A is a top view of another embodiment of an on-skin sensor control unit after insertion of an introducer and a sensor, according to the invention.
• FIG. 11B is a top view of one embodiment of a mounting unit of the on-skin sensor control unit ofFIG. 11A.
• FIG. 11C is a top view of one embodiment of a housing for at least a portion of the electronics of the on-skin sensor control unit ofFIG. 11A.
• FIG. 11D is a bottom view of the housing ofFIG. 11C.
• FIG. 11E is a top view of the on-skin sensor control unit ofFIG. 11A with a cover of the housing removed.
• FIG. 12 depicts an introducer, sensor, insertion gun and mounting unit, which can be assembled and sold together in an insertion kit.
• FIG. 13 is a perspective view showing a preferred commercial embodiment of a sensor inserter and adhesive mount constructed according to the invention.
• FIG. 14 is a perspective view of the adhesive mount and sensor attached to the patient's skin.
• FIG. 15 is a perspective view of the transmitter attached to the adhesive mount.
• FIG. 16 is an exploded perspective view of the preferred commercial embodiment ofFIG. 13.
• FIG. 17 is a side elevation view of the preferred commercial embodiment ofFIG. 13.
• FIG. 18 is an end elevation view of the preferred commercial embodiment ofFIG. 13.
• FIG. 19 is a cross-sectional view taken along line19-19 inFIG. 18.
• FIG. 20 is a cross-sectional view taken along line20-20 inFIG. 17.
• FIG. 21 is a broken away view similar toFIG. 20, showing the shuttle in the neutral position.
• FIG. 22 is a broken away view similar toFIG. 20, showing the shuttle in the cocked position.
• FIG. 23 is a broken away view similar toFIG. 20, showing the shuttle in the insertion position.
• FIG. 24 is a cross-sectional view taken along line24-24 inFIG. 17.
• FIG. 25 is a perspective view of a transcutaneously implantable sensor.
• FIG. 26A is a perspective view of a sensor introducer.
• FIG. 26B is a bottom view of the introducer shown inFIG. 26A.
• FIG. 27 is a perspective view of a shuttle member.
• FIG. 28 is a top plan view of an oversized adhesive tape.
• FIG. 29 is a perspective view of the transmitter attached to the adhesive mount and showing the sensor sandwiched therebetween.
• FIG. 30 is a perspective view of the interconnect on one end of the transmitter.
• FIG. 31 is an enlarged perspective view of the interconnect ofFIG. 30 with the seal and one spring removed for clarity.
• FIG. 32 is an enlarged perspective view of the interconnect seal.
• FIG. 33A is a perspective view of an alternative embodiment of a sensor inserter kit.
• FIG. 33B is an exploded view of some of the components shown assembled inFIG. 33A.
• While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
DETAILED DESCRIPTION OF THE INVENTION
• The present invention is applicable to an analyte monitoring system using an implantable sensor for the in vivo determination of a concentration of an analyte, such as glucose or lactate, in a fluid. The sensor can be, for example, subcutaneously implanted in a patient for the continuous or periodic monitoring an analyte in a patient's interstitial fluid. This can then be used to infer the glucose level in the patient's bloodstream. Other in vivo analyte sensors can be made, according to the invention, for insertion into a vein, artery, or other portion of the body containing fluid. The analyte monitoring system is typically configured for monitoring the level of the analyte over a time period which may range from days to weeks or longer.
• The analyte monitoring systems of the present invention can be utilized under a variety of conditions. The particular configuration of a sensor and other units used in the analyte monitoring system may depend on the use for which the analyte monitoring system is intended and the conditions under which the analyte monitoring system will operate. One embodiment of the analyte monitoring system includes a sensor configured for implantation into a patient or user. For example, implantation of the sensor may be made in the arterial or venous systems for direct testing of analyte levels in blood. Alternatively, a sensor may be implanted in the interstitial tissue for determining the analyte level in interstitial fluid. This level may be correlated and/or converted to analyte levels in blood or other fluids. The site and depth of implantation may affect the particular shape, components, and configuration of the sensor. Subcutaneous implantation may be preferred, in some cases, to limit the depth of implantation of the sensor. Sensors may also be implanted in other regions of the body to determine analyte levels in other fluids. Examples of suitable sensor for use in the analyte monitoring systems of the invention are described in U.S. patent application Ser. No. 09/034,372 and Ser. No. 09/753,746 (the complete parent application to this CIP), both incorporated herein by reference.
• One embodiment of theanalyte monitoring system40 for use with animplantable sensor42, and particularly for use with a subcutaneously implantable sensor, is illustrated in block diagram form inFIG. 1. Theanalyte monitoring system40 includes, at minimum, asensor42, a portion of which is configured for implantation (e.g., subcutaneous, venous, or arterial implantation) into a patient, and asensor control unit44. Thesensor42 is coupled to thesensor control unit44 which is typically attached to the skin of a patient. Thesensor control unit44 operates thesensor42, including, for example, providing a voltage across the electrodes of thesensor42 and collecting signals from thesensor42. Thesensor control unit44 may evaluate the signals from thesensor42 and/or transmit the signals to one or more optional receiver/display units46,48 for evaluation. Thesensor control unit44 and/or the receiver/display units46,48 may display or otherwise communicate the current level of the analyte. Furthermore, thesensor control unit44 and/or the receiver/display units46,48 may indicate to the patient, via, for example, an audible, visual, or other sensory-stimulating alarm, when the level of the analyte is at or near a threshold level. In some embodiments, a electrical shock can be delivered to the patient as a warning through one of the electrodes or the optional temperature probe of the sensor. For example, if glucose is monitored then an alarm may be used to alert the patient to a hypoglycemic or hyperglycemic glucose level and/or to impending hypoglycemia or hyperglycemia.
• Asensor42 includes at least one workingelectrode58 formed on asubstrate50, as shown inFIG. 2. Thesensor42 may also include at least one counter electrode60 (or counter/reference electrode) and/or at least one reference electrode62. Thesubstrate50 of the sensor may be formed using a variety of non-conducting materials, including, for example, polymeric or plastic materials and ceramic materials. Suitable materials for aparticular sensor42 may be determined, at least in part, based on the desired use of thesensor42 and properties of the materials.
• In some embodiments, the substrate is flexible. For example, if thesensor42 is configured for implantation into a patient, then thesensor42 may be made flexible (although rigid sensors may also be used for implantable sensors) to reduce pain to the patient and damage to the tissue caused by the implantation of and/or the wearing of thesensor42. Aflexible substrate50 often increases the patient's comfort and allows a wider range of activities. Suitable materials for aflexible substrate50 include, for example, non-conducting plastic or polymeric materials and other non-conducting, flexible, deformable materials. Examples of useful plastic or polymeric materials include thermoplastics such as polycarbonates, polyesters (e.g., Mylar™ and polyethylene terephthalate (PET)), polyvinyl chloride (PVC), polyurethanes, polyethers, polyamides, polyimides, or copolymers of these thermoplastics, such as PETG (glycol-modified polyethylene terephthalate).
• In other embodiments, thesensors42 are made using a relativelyrigid substrate50 to, for example, provide structural support against bending or breaking. Examples of rigid materials that may be used as thesubstrate50 include poorly conducting ceramics, such as aluminum oxide and silicon dioxide. One advantage of animplantable sensor42 having a rigid substrate is that thesensor42 may have a sharp point and/or a sharp edge to aid in implantation of asensor42 without an additional introducer.
• It will be appreciated that formany sensors42 and sensor applications, both rigid and flexible sensors will operate adequately. The flexibility of thesensor42 may also be controlled and varied along a continuum by changing, for example, the composition and/or thickness of thesubstrate50.
• In addition to considerations regarding flexibility, it is often desirable thatimplantable sensors42 should have asubstrate50 which is non-toxic. Preferably, thesubstrate50 is approved by one or more appropriate governmental agencies or private groups for in vivo use.
• Although thesubstrate50 in at least some embodiments has uniform dimensions along the entire length of thesensor42, in other embodiments, thesubstrate50 has adistal end67 and aproximal end65 withdifferent widths53,55, respectively, as illustrated inFIG. 2. In these embodiments, thedistal end67 of thesubstrate50 may have a relativelynarrow width53. Forsensors42 which are implantable into the subcutaneous tissue or another portion of a patient's body, thenarrow width53 of thedistal end67 of thesubstrate50 may facilitate the implantation of thesensor42. Often, the narrower the width of thesensor42, the less pain the patient will feel during implantation of the sensor and afterwards. Thesensor42 is designed to be a replaceable component in an implantable analyte monitor. Typically, thesensor42 is capable of operation over a period of days. Preferably, the period of operation is at least three days. Thesensor42 can then be removed and replaced with a new sensor.
• Anintroducer120 can be used to subcutaneously insert thesensor42 into the patient, as illustrated inFIG. 3. Theintroducer120 is typically formed using structurally rigid materials, such as metal or rigid plastic. Preferred materials include stainless steel and ABS (acrylonitrile-butadiene-styrene) plastic. In some embodiments, theintroducer120 is pointed and/or sharp at thetip121 to facilitate penetration of the skin of the patient. A sharp, thin introducer may reduce pain felt by the patient upon insertion of thesensor42. In other embodiments, thetip121 of theintroducer120 has other shapes, including a blunt or flat shape. These embodiments may be particularly useful when theintroducer120 does not penetrate the skin but rather serves as a structural support for thesensor42 as thesensor42 is pushed into the skin.
• Theintroducer120 may have a variety of cross-sectional shapes, as shown inFIGS. 4A,4B, and4C. Theintroducer120 illustrated inFIG. 4A is a flat, planar, pointed strip of rigid material which may be attached or otherwise coupled to thesensor42 to ease insertion of thesensor42 into the skin of the patient, as well as to provide structural support to thesensor42 during insertion. Theintroducers120 ofFIGS. 4B and 4C are U- or V-shaped implements that support thesensor42 to limit the amount that thesensor42 may bend or bow during insertion. Thecross-sectional width124 of theintroducers120 illustrated inFIGS. 4B and 4C is typically 1 mm or less, preferably 700 μm or less, more preferably 500 μm or less, and most preferably 300 μm or less. Thecross-sectional height126 of theintroducer120 illustrated inFIGS. 4B and 4C is typically about 1 mm or less, preferably about 700 μM or less, and more preferably about 500 μm or less.
• Thesensor42 itself may include optional features to facilitate insertion. For example, thesensor42 may be pointed at thetip123 to ease insertion, as illustrated inFIG. 3. In addition, thesensor42 may include abarb125 which helps retain thesensor42 in the subcutaneous tissue of the patient. Thebarb125 may also assist in anchoring thesensor42 within the subcutaneous tissue of the patient during operation of thesensor42. However, thebarb125 is typically small enough that little damage is caused to the subcutaneous tissue when thesensor42 is removed for replacement. Thesensor42 may also include anotch127 that can be used in cooperation with a corresponding structure (not shown) in the introducer to apply pressure against thesensor42 during insertion, but disengage as theintroducer120 is removed. One example of such a structure in the insertion device is a rod (not shown) between two opposing sides of anintroducer120 and at an appropriate height of theintroducer120.
• In operation, thesensor42 is placed within or next to theintroducer120 and then a force is provided against theintroducer120 and/orsensor42 to carry thesensor42 into the skin of the patient. In one embodiment, the force is applied to thesensor42 to push the sensor into the skin, while theintroducer120 remains stationary and provides structural support to thesensor42. Alternatively, the force is applied to theintroducer120 and optionally to thesensor42 to push a portion of both thesensor42 and theintroducer120 through the ski of the patient and into the subcutaneous tissue. Theintroducer120 is optionally pulled out of the skin and subcutaneous tissue with thesensor42 remaining in the subcutaneous tissue due to frictional forces between thesensor42 and the patient's tissue. If thesensor42 includes theoptional barb125, then this structure may also facilitate the retention of thesensor42 within the interstitial tissue as the barb catches in the tissue.
• The force applied to theintroducer120 and/or thesensor42 may be applied manually or mechanically. Preferably, thesensor42 is reproducibly inserted through the skin of the patient. In one embodiment, an insertion gun is used to insert the sensor. One example of aninsertion gun200 for inserting asensor42 is shown inFIG. 9. Theinsertion gun200 includes ahousing202 and acarrier204. Theintroducer120 is typically mounted on thecarrier204 and thesensor42 is pre-loaded into theintroducer120. Thecarrier204 drives thesensor42 and, optionally, theintroducer120 into the skin of the patient using, for example, a cocked or wound spring, a burst of compressed gas, an electromagnet repelled by a second magnet, or the like, within theinsertion gun200. In some instances, for example, when using a spring, thecarrier204 andintroducer120 may be moved, cocked, or otherwise prepared to be directed towards the skin of the patient.
• After thesensor42 is inserted, theinsertion gun200 may contain a mechanism which pulls theintroducer120 out of the skin of the patient. Such a mechanism may use a spring, electromagnet, or the like to remove theintroducer120.
• The insertion gun may be reusable. Theintroducer120 is often disposable to avoid the possibility of contamination. Alternatively, theintroducer120 may be sterilized and reused. In addition, theintroducer120 and/or thesensor42 may be coated with an anticlotting agent to prevent fouling of thesensor42.
• In one embodiment, thesensor42 is injected between 2 to 12 mm into the interstitial tissue of the patient for subcutaneous implantation. Preferably, the sensor is injected 3 to 9 mm, and more preferably 5 to 7 mm, into the interstitial tissue. Other embodiments of the invention, may include sensors implanted in other portions of the patient, including, for example, in an artery, vein, or organ. The depth of implantation varies depending on the desired implantation target.
• Although thesensor42 may be inserted anywhere in the body, it is often desirable that the insertion site be positioned so that the on-skinsensor control unit44 can be concealed. In addition, it is often desirable that the insertion site be at a place on the body with a low density of nerve endings to reduce the pain to the patient. Examples of preferred sites for insertion of thesensor42 and positioning of the on-skinsensor control unit44 include the abdomen, thigh, leg, upper arm, and shoulder.
• An insertion angle is measured from the plane of the skin (i.e., inserting the sensor perpendicular to the skin would be a 90° insertion angle). Insertion angles usually range from 10 to 90°, typically from 15 to 60°, and often from 30 to 45°.
On-Skin Sensor Control Unit
• The on-skinsensor control unit44 is configured to be placed on the skin of a patient. The on-skinsensor control unit44 is optionally formed in a shape that is comfortable to the patient and which may permit concealment, for example, under a patient's clothing. The thigh, leg, upper arm, shoulder, or abdomen are convenient parts of the patient's body for placement of the on-skinsensor control unit44 to maintain concealment. However, the on-skinsensor control unit44 may be positioned on other portions of the patient's body. One embodiment of the on-skinsensor control unit44 has a thin, oval shape to enhance concealment, as illustrated inFIGS. 5-7. However, other shapes and sizes may be used.
• The particular profile, as well as the height, width, length, weight, and volume of the on-skinsensor control unit44 may vary and depends, at least in part, on the components and associated functions included in the on-skinsensor control unit44, as discussed below. For example, in some embodiments, the on-skinsensor control unit44 has a height of 1.3 cm or less, and preferably 0.7 cm or less. In some embodiments, the on-skinsensor control unit44 has a weight of 90 grams or less, preferably 45 grams or less, and more preferably 25 grams or less. In some embodiments, the on-skinsensor control unit44 has a volume of about 15 cm³or less, preferably about 10 cm³or less, more preferably about 5 cm³or less, and most preferably about 2.5 cm³or less.
• The on-skinsensor control unit44 includes ahousing45, as illustrated inFIGS. 5-7. Thehousing45 is typically formed as a single integral unit that rests on the skin of the patient. Thehousing45 typically contains most or all of the electronic components, described below, of the on-skinsensor control unit44. The on-skinsensor control unit44 usually includes no additional cables or wires to other electronic components or other devices. If the housing includes two or more parts, then those parts typically fit together to form a single integral unit.
• In some embodiments,conductive contacts80 are provided on the exterior of thehousing45. In other embodiments, theconductive contacts80 are provided on the interior of thehousing45, for example, within a hollow or recessed region.
• In some embodiments, thehousing45 of the on-skinsensor control unit44 is a single piece. Theconductive contacts80 may be formed on the exterior of thehousing45 or on the interior of thehousing45 provided there is aport78 in thehousing45 through which thesensor42 can be directed to access theconductive contacts80.
• In other embodiments, thehousing45 of the on-skinsensor control unit44 is formed in at least two separate portions that fit together to form thehousing45, for example, abase74 and acover76, as illustrated inFIGS. 5-7. The two or more portions of thehousing45 may be entirely separate from each other. Alternatively, at least some of the two or more portions of thehousing45 may be connected together, for example, by a hinge, to facilitate the coupling of the portions to form thehousing45 of the on-skinsensor control unit44.
• These two or more separate portions of thehousing45 of the on-skinsensor control unit44 may have complementary, interlocking structures, such as, for example, interlocking ridges or a ridge on one component and a complementary groove on another component, so that the two or more separate components may be easily and/or firmly coupled together. This may be useful, particularly if the components are taken apart and fit together occasionally, for example, when a battery orsensor42 is replaced. However, other fasteners may also be used to couple the two or more components together, including, for example, screws, nuts and bolts, nails, staples, rivets, or the like. In addition, adhesives, both permanent or temporary, may be used including, for example, contact adhesives, pressure sensitive adhesives, glues, epoxies, adhesive resins, and the like.
• Typically, thehousing45 is at least water resistant to prevent the flow of fluids into contact with the components in the housing, including, for example, theconductive contacts80. Preferably, the housing is waterproof. In one embodiment, two or more components of thehousing45, for example, thebase74 and thecover76, fit together tightly to form a hermetic, waterproof, or water resistant seal so that fluids can not flow into the interior of the on-skinsensor control unit44. This may be useful to avoid corrosion currents and/or degradation of items within the on-skinsensor control unit44, such as the conductive contacts, the battery, or the electronic components, particularly when the patient engages in such activities as showering, bathing, or swimming.
• Water resistant, as used herein, means that there is no penetration of water through a water resistant seal or housing when immersed in water at a depth of one meter at sea level. Waterproof, as used herein, means that there is no penetration of water through the waterproof seal or housing when immersed in water at a depth of ten meters, and preferably fifty meters, at sea level. It is often desirable that the electronic circuitry, power supply (e.g., battery), and conductive contacts of the on-skin sensor control unit, as well as the contact pads of the sensor, are contained in a water resistant, and preferably, a waterproof, environment.
• The on-skinsensor control unit44 is typically attached to theskin75 of the patient, as illustrated inFIG. 8. The on-skinsensor control unit44 may be attached by a variety of techniques including, for example, by adhering the on-skinsensor control unit44 directly to theskin75 of the patient with an adhesive provided on at least a portion of thehousing45 of the on-skinsensor control unit44 which contacts theskin75, by suturing the on-skinsensor control unit44 to theskin75 through suture openings (not shown) in thesensor control unit44, or by strapping the on-skinsensor control unit44 to theskin75.
• Another method of attaching thehousing45 of the on-skinsensor control unit44 to theskin75 includes using a mounting unit,77. The mountingunit77 is often a part of the on-skinsensor control unit44. One example of a suitable mountingunit77 is a double-sided adhesive strip, one side of which is adhered to a surface of the skin of the patient and the other side is adhered to the on-skinsensor control unit44. In this embodiment, the mountingunit77 may have anoptional opening79 which is large enough to allow insertion of thesensor42 through theopening79. Alternatively, the sensor may be inserted through a thin adhesive and into the skin.
• A variety of adhesives may be used to adhere the on-skinsensor control unit44 to theskin75 of the patient, either directly or using the mountingunit77, including, for example, pressure sensitive adhesives (PSA) or contact adhesives. Preferably, an adhesive is chosen which is not irritating to all or a majority of patients for at least the period of time that aparticular sensor42 is implanted in the patient. Alternatively, a second adhesive or other skin-protecting compound may be included with the mounting unit so that a patient, whose skin is irritated by the adhesive on the mountingunit77, can cover his skin with the second adhesive or other skin-protecting compound and then place the mountingunit77 over the second adhesive or other skin-protecting compound. This should substantially prevent the irritation of the skin of the patient because the adhesive on the mountingunit77 is no longer in contact with the skin, but is instead in contact with the second adhesive or other skin-protecting compound.
• Returning toFIG. 8, when thesensor42 is changed, the on-skinsensor control unit44 may be moved to a different position on theskin75 of the patient, for example, to avoid excessive irritation. Alternatively, the on-skinsensor control unit44 may remain at the same place on the skin of the patient until it is determined that theunit44 should be moved.
• Another embodiment of a mountingunit77 used in an on-skinsensor control unit44 is illustrated inFIGS. 10A and 10B. The mountingunit77 and ahousing45 of an on-skinsensor control unit44 are mounted together in, for example, an interlocking manner, as shown inFIG. 10A. The mountingunit77 is formed, for example, using plastic or polymer materials, including, for example, polyvinyl chloride, polyethylene, polypropylene, polystyrene, ABS polymers, and copolymers thereof. The mountingunit77 may be formed using a variety of techniques including, for example, injection molding, compression molding, casting, and other molding methods.
• The mountingunit77 typically includes an adhesive on a bottom surface of the mountingunit77 to adhere to the skin of the patient or the mountingunit77 is used in conjunction with, for example, double-sided adhesive tape or the like. The mountingunit77 typically includes anopening79 through which thesensor42 is inserted, as shown inFIG. 10B. The mountingunit77 may also include asupport structure220 for holding thesensor42 in place and against theconductive contacts80 on the on-skinsensor control unit42. The mountingunit77, also, optionally, includes apositioning structure222, such as an extension of material from the mountingunit77, that corresponds to a structure (not shown), such as an opening, on thesensor42 to facilitate proper positioning of thesensor42, for example, by aligning the two complementary structures.
• In another embodiment, a coupled mountingunit77 andhousing45 of an on-skinsensor control unit44 is provided on anadhesive patch204 with anoptional cover206 to protect and/or confine thehousing45 of the on-skinsensor control unit44, as illustrated inFIG. 11A. The optional cover may contain an adhesive or other mechanism for attachment to thehousing45 and/or mountingunit77. The mountingunit77 typically includes anopening49 through which asensor42 is disposed, as shown inFIG. 11B. Theopening49 may optionally be configured to allow insertion of thesensor42 through theopening49 using anintroducer120 or insertion gun200 (seeFIG. 9). Thehousing45 of the on-skinsensor control unit44 has abase74 and acover76, as illustrated inFIG. 11C. A bottom view of thehousing45, as shown inFIG. 11D, illustratesports230 through which conductive contacts (not shown) extend to connect with contact pads on thesensor42. Aboard232 for attachment of circuit components may optionally be provided within the on-skinsensor control unit44, as illustrated inFIG. 11E.
• In some embodiments, the adhesive on the on-skinsensor control unit44 and/or on any of the embodiments of the mountingunit77 is water resistant or waterproof to permit activities such as showering and/or bathing while maintaining adherence of the on-skinsensor control unit44 to theskin75 of the patient and, at least in some embodiments, preventing water from penetrating into thesensor control unit44. The use of a water resistant or waterproof adhesive combined with a water resistant orwaterproof housing45 protects the components in thesensor control unit44 and the contact between theconductive contacts80 and thesensor42 from damage or corrosion. An example of a non-irritating adhesive that repels water is Tegaderm (3M, St. Paul, Minn.).
• In one embodiment, the on-skinsensor control unit44 includes asensor port78 through which thesensor42 enters the subcutaneous tissue of the patient, as shown inFIGS. 5 to 7. Thesensor42 may be inserted into the subcutaneous tissue of the patient through thesensor port78. The on-skinsensor control unit44 may then be placed on the skin of the patient with thesensor42 being threaded through thesensor port78. If thehousing45 of thesensor42 has, for example, abase74 and acover76, then thecover76 may be removed to allow the patient to guide thesensor42 into the proper position for contact with theconductive contacts80.
• Alternatively, if theconductive contacts80 are within thehousing45 the patient may slide thesensor42 into thehousing45 until contact is made between thecontact pads49 and theconductive contacts80. Thesensor control unit44 may have a structure which obstructs the sliding of thesensor42 further into the housing once thesensor42 is properly positioned with thecontact pads49 in contact with theconductive contacts80.
• In other embodiments, theconductive contacts80 are on the exterior of the housing45 (see e.g.,FIGS. 10A-10B and11A-11E). In these embodiments, the patient guides thecontacts pads49 of thesensor42 into contact with theconductive contacts80. In some cases, a guiding structure may be provided on thehousing45 which guides thesensor42 into the proper position. An example of such a structure includes a set of guiding rails extending from thehousing45 and having the shape of thesensor42.
• In some embodiments, when thesensor42 is inserted using an introducer120 (seeFIG. 3), the tip of theintroducer120 or optional insertion gun200 (seeFIG. 9) is positioned against the skin or the mountingunit77 at the desired insertion point. In some embodiments, theintroducer120 is positioned on the skin without any guide. In other embodiments, theintroducer120 orinsertion gun200 is positioned using guides (not shown) in the mountingunit77 or other portion of the on-skinsensor control unit44. In some embodiments, the guides, opening79 in the mountingunit77 and/orsensor port78 in thehousing45 of the on-skinsensor control unit44 have a shape which is complementary to the shape of the tip of theintroducer120 and/orinsertion gun200 to limit the orientation of theintroducer120 and/orinsertion gun200 relative to theopening79 and/orsensor port78. The sensor can then be subcutaneously inserted into the patient by matching the complementary shape of theopening79 orsensor port78 with theintroducer120 and/orinsertion gun200.
• In some embodiments, the shapes of a) the guides, opening79, orsensor port78, and (b) theintroducer120 orinsertion gun200 are configured such that the two shapes can only be matched in a single orientation. This aids in inserting thesensor42 in the same orientation each time a new sensor is inserted into the patient. This uniformity in insertion orientation may be required in some embodiments to ensure that thecontact pads49 on thesensor42 are correctly aligned with appropriateconductive contacts80 on the on-skinsensor control unit44. In addition, the use of the insertion gun, as described above, may ensure that thesensor42 is inserted at a uniform, reproducible depth.
• An exemplary on-skinsensor control unit44 can be prepared and used in the following manner. A mountingunit77 having adhesive on the bottom is applied to the skin. An insertion gun200 (seeFIG. 9) carrying thesensor42 and theintroducer120 is positioned against the mountingunit77. Theinsertion gun200 and mountingunit77 are optionally designed such that there is only one position in which the two properly mate. Theinsertion gun200 is activated and a portion of thesensor42 and optionally a portion of theintroducer120 are driven through the skin into, for example, the subcutaneous tissue. Theinsertion gun200 withdraws theintroducer120, leaving the portion of thesensor42 inserted through the skin. Thehousing45 of the on-skin control unit44 is then coupled to the mountingunit77. Optionally, thehousing45 and the mountingunit77 are formed such that there is only one position in which the two properly mate. The mating of thehousing45 and the mountingunit77 establishes contact between the contact pads49 (see e.g.,FIG. 2) on thesensor42 and theconductive contacts80 on the on-skinsensor control unit44. Optionally, this action activates the on-skinsensor control unit44 to begin operation.
• The introducer, sensor, insertion gun and mounting unit can be manufactured, marketed, or sold as a unit. For example,FIG. 12 depicts anintroducer270,sensor272,insertion gun274 and mountingunit276, which can be assembled (as indicated by the arrows) and sold together in an insertion kit. In such an embodiment of an insertion kit, theinsertion gun274 can be packaged in a pre-loaded fashion, with anintroducer270 andsensor272 mated or otherwise coupled, the matedsensor272 andintroducer270 loaded upon thecarrier278 of the insertion gun, and with a mountingunit276 already mated with the end of theinsertion gun274.
• In one embodiment, theinsertion gun274 is packaged in a state where it is ready to thrust the sensor272 (and perhaps introducer270) into subcutaneous tissue. For example, theinsertion gun274 can be packaged in a “cocked” state, such that the thrusting force used to introduce thesensor272 into the subcutaneous tissue is stored in the device as potential energy (in the case of the embodiment depicted inFIG. 12, theinsertion gun274 would be “cocked” by compressing its spring280, thus storing potential energy within the coils of the spring). Preferably, aninsertion gun274 packaged in such a manner employs a “safety”, a barrier to prevent the release of the stored potential energy. The barrier is removed in order to permit the potential energy to be released. Within the context of the embodiment presented inFIG. 12, an example of a safety is a pin (not pictured) that impedes the spring from expanding, once compressed. Thus, an insertion kit so embodied can be obtained at a place of purchase, removed from its package, and used after removal of the safety, without necessitating additional steps. Alternatively, theinsertion gun274 can be packaged in the above-described pre-loaded configuration, but without being “cocked”. Thus, an insertion kit with an “uncocked”insertion gun274 can be obtained at a place of purchase, removed from its package, cocked, and used. To facilitate the insertion kit being ready to use with minimal user-exercised steps, the insertion kit can be sterilized prior to packaging. Examples of acceptable sterilizing techniques include exposing the elements of the insertion kit to gamma radiation or an e-beam.
• Referring toFIGS. 13-33, preferred commercial embodiments of a sensor inserter constructed according to the invention will now be described.FIG. 13 shows an overall perspective view of asensor inserter kit300 comprising a single-use sensor inserter310 and a single-useadhesive mount312 removably attached to the bottom thereof.
• As an overview of the operation ofinserter kit300, the kit comes packaged generally as shown inFIG. 13 with a sensor314 (best seen inFIGS. 16 and 25) preloaded withininserter310 and withinserter310 in a “cocked” state. After preparing an insertion site on the skin, typically in the abdominal region, the patient removesupper liner316 andlower liner318 fromadhesive mount312 to expose the bottom surface and a portion of the top surface of an adhesive tape320 (best seen inFIG. 16) located beneathmount312.Mount312, withinserter310 attached, is then applied to the patient's skin at the insertion site.Safety lock tabs322 are squeezed together to allowactuator button324 to be pressed causinginserter310 to fire, thereby insertingsensor314 into the patient's skin with a predetermined velocity and force. Oncesensor314 has been inserted into the skin, the patient removes inserter310 frommount312 by pressingrelease tabs326 on opposite sides ofinserter310 and liftinginserter310 away frommount312.
• Referring toFIG. 14,mount312 is shown adhered to a patient'sskin328 withsensor314 already inserted. Onceinserter310 is removed frommount312,transmitter330 can be slid into place. The circuitry oftransmitter330 makes electrical contact with the contact pads onsensor314 aftertransmitter330 is fully seated onmount312. Once initialization and synchronization procedures are completed, electrochemical measurements fromsensor314 can be sent wirelessly fromtransmitter330 to aportable receiver332, as shown inFIG. 15.Sensor314,mount312 andtransmitter330 remain in place on the patient for a predetermined period, currently envisioned to be three days. These components are then removed so thatsensor314 and mount312 can be properly discarded. The entire procedure above can then be repeated with anew inserter310,sensor314 and mount312, reusingtransmitter330 andreceiver332.
• Referring toFIG. 16, thepreferred inserter kit300 is assembled as shown from the following components:housing334,actuator button324,drive spring336,shuttle338, introducer sharp340,sensor314,retraction spring342,inserter base344,upper liner316,adhesive mount312,adhesive tape320, andlower liner318.
• Sensor314 has amain surface346 slidably mounted betweenU-shaped rails348 of introducer sharp340 and releasably retained there bysensor dimple350 which engagesintroducer dimple352. Introducer sharp340 is mounted to face354 ofshuttle338, such as with adhesive, heat stake or ultrasonic weld.Sensor314 also has asurface356 that extends orthogonally frommain surface346 and just beneath a drivingsurface358 ofshuttle338 when mounted thereon (details of these features are better shown in FIGS.19 and25-27.)
• Shuttle338 is slidably and non-rotabably constrained onbase344 byarcuate guides360. As best seen inFIGS. 19,24 and27,shuttle338 is generally formed by anouter ring362 and an inner cup-shapedpost364 connected by twobridges366.Bridges366 slide between the twoslots368 formed betweenguides360 and allowshuttle338 to travel alongguides360 without rotating.Retraction spring342 is captivated at its outer circumference byguides360, at its bottom by thefloor370 ofbase344, at its top bybridges366, and at its inner circumference by the outer surface ofshuttle post364.Drive spring336 is captivated at its bottom and outer circumference by the inside surface ofshuttle post364, at its top by theceiling372 insideactuator button324, and at its inner circumference bystem374 depending fromceiling372. Whendrive spring336 is compressed betweenactuator button324 andshuttle338 it urgesshuttle338 towardsbase344. Whenretraction spring342 is compressed betweenshuttle338 andbase344, it urgesshuttle338 towardsactuator button324.
• Actuator button324 is slidably received withinhousing334 from below and resides in opening376 at the top ofhousing334 with limited longitudinal movement.Arms378 on each side ofactuator button324 travel inchannels380 along the inside walls ofhousing334, as best seen inFIG. 20. Longitudinal movement ofactuator button324 is limited in one direction by thebase378 ofarms378 contacting the edge of opening376 at the top ofhousing334, and in the other direction by the distal ends384 ofarms378 contactingstops386 inchannels380.Slots388 are preferably provided in the top ofhousing334 for ease of housing manufacture and so tools can be inserted to inwardly compressarms378 beyondstops386 to allowactuator button324 to be removed fromhousing334 if needed.
• Whensensor314,introducer340,shuttle338,retraction spring342,drive spring336 andactuator button324 are assembled betweenbase344 andhousing334 as shown inFIG. 16 and described above,housing334 is snapped into place onbase344.Base344 is held ontohousing334 byupper base barbs390 that engageupper openings392 inhousing334, and lower base barbs394 (best seen inFIG. 17) that engagelower openings396 inhousing334.Slots398 and400 are provided for ease of manufacture ofhousing334, andbase344 is preferably removable fromhousing334 with tools if needed.
• Referring toFIG. 19,actuator button324 is preferably provided withsafety lock tabs322 hingedly formed on opposite ends.Tabs322 can be urged from a relaxed outward position to a flexed inward position. When in the normal outward position, shoulders402 on the outer surfaces oftabs322 engage therim404 of opening376 to prevent theactuator button324 from being depressed, thereby avoiding accidental firing ofinserter310.Tabs322 can be squeezed inward just enough to clear therim404 of opening376 while pressing theactuator button324 down to fire the inserter. Alternatively,tabs322 can be squeezed further inward so thatbarbs406 on the inside edges can engagecatches408 located on a center portion ofactuator button324, thereby defeating the safety lock to allow later firing by simply pressing down on theactuator button324. Preferably, upwardly extendinggrips410 are provided ontabs322 for better visual indication of safety lock status and actuation control.
• Referring toFIG. 20,shuttle338 is provided with laterally extendingbarbed fingers412 which travel inchannels380 along the inside walls ofhousing334. Whenshuttle338 is inserted up intohousing334 far enough,barbed fingers412 momentarily deflect inward and then snap outward again to catch on stops386. In this “cocked” position as shown,drive spring336 is compressed and urgingshuttle338 towardsbase344, butbarbed fingers412 catching onstops386 prevent such travel.
• Referring toFIGS. 21-23, the sequence of loading, cocking, arming, firing, and automatic retraction ofinserter310 will be described. It is envisioned that in production,inserters310 will be fabricated and fully assembled by one vender except forsensor314, which will be supplied and installed by a second vendor in a sterile environment. Accordingly,inserter310 will be manufactured and shipped to the sensor vendor in a neutral state, as shown inFIG. 21. Ahole414 provided through the center ofactuator button324 allows the sensor vendor to insert a pin (manually or by automated machinery, not shown) throughhole414 to driveshuttle338 towardsbase344 in a controlled fashion and hold it there against the force ofretraction spring342. This will cause introducer sharp340 to be extended through base344 (as shown inFIG. 23) so thatsensor314 can be loaded intointroducer340. When the pin is removed,shuttle338,introducer340 andsensor314 will retract to the neutral position. The sensor vendor can then cock the loadedinserter310 before shipment by pushing another pin (not shown) from the opposite direction through acentral hole416 in base344 (withmount312 removed) until the pin contacts dimple418 formed in the bottom ofshuttle338. By pushingshuttle338 towardsactuator button324 untilbarbed fingers412clear stops386, theinserter310 is cocked (as shown inFIG. 22.)
• Referring toFIG. 22,inserter310 is preferably received by the patient in the cocked position as shown. To useinserter310, the patient appliesmount312 to the mounting site and disables the safety mechanism as previously described, and then pushesactuator button324 against the force ofdrive spring336. Asactuator button324 travels towardbase344, drive cam surfaces420 onarms378 contact rampedsurfaces422 ofbarbed fingers412 and urge them inward. Whenfingers412 are driven inward enough to clearstops386,shuttle338 is driven bydrive spring336 with a predetermined speed and force to an insertion position, as shown inFIG. 23.
• Referring toFIG. 23,inserter310 is shown in the insertion position with thetail424 of introducer sharp340 extending throughbase344 and mount312 into the skin of the patient.FIG. 23 shows shuttle338 in a fully extended position with itslower surface426 bottomed out onbase344. However, the lowerorthogonal surface356 ofsensor314 will contact an exposed sensor contact portion428 (best seen inFIGS. 14 and 16) on top ofadhesive tape320 supported from below by the patient's skin, and therefore will typically stop traveling before reaching the fully bottomed out position shown.Tail424 of introducer sharp340 provides rigidity and askin piercing edge430 for allowing theflexible tail431 ofsensor314 to be implanted in the patient's skin. After providing this function, introducer sharp340 is immediately removed from the patient and retracted into a safe position insidehousing334 as retraction spring342 (which has been compressed by the travel of the shuttle) pushesshuttle338 back towards actuator cap.Sensor314 is pulled fromintroducer340 and held in place by thesensor contact portion428 on top ofadhesive tape320 adhering toorthogonal surface356 ofsensor314. The geometries ofsensor dimple350 andmating introducer dimple352 are chosen to create a separation force between them that is less than the adhesion force oftape320 onorthogonal surface356, but great enough to retainsensor314 inintroducer340 during typical shipping and product handling shock loads. Drivingsurface358 beneathshuttle338 presses down on top oforthogonal surface356 to ensure good contact withadhesive tape320 beforeshuttle338 retracts withintroducer340. As discussed above with previous embodiments, barb(s) onsensor tail431 can be employed to further anchor the sensor in its operating position.
• Referring again toFIG. 21,retraction spring342 will returnshuttle338 to the neutral position as shown after firing, but withoutsensor314 which remains inserted in patient's skin (not still inintroducer340 as shown here.)Drive spring336 is preferably designed to be stiffer thanretraction spring342 so thatshuttle338 oscillations are quickly dampened out, and so introducer sharp340 does not return tosensor314 or the patient to cause injury. Withsensor314 now inserted in the patient's skin,inserter310 can be removed frommount312 by inwardly flexingrelease tabs326 on opposite sides ofinserter310 to remove latch hooks432 frommount channels434 and then liftinginserter310 away frommount312. Introducer sharp340 remains protected insidehousing334 during disposal ofinserter310.Transmitter330 can now be slid into place onmount312 as previously described.
• Referring toFIG. 28, an alternative embodiment ofadhesive tape320′ is shown. Thisoversized tape320′ has the advantage of holdingtransmitter330 in place even when fairly large forces are placed on it. In this embodimentadhesive tape320′ has a double-sided portion436 (adhesive on both top and bottom sides) residing betweenmount312 and the patient's skin, and a single-sided portion438 outwardly extending from the double-sided portion436, preferably in all directions, for adhering just to the patient's skin. In the previous embodiment, it is difficult toseparate mount312 from the skin merely with tension forces, but applying a force to just one side ofmount312 results in a high peeling force being applied to that edge of theadhesive tape320 which causestape320 to peel off of the skin. In contrast, any force applied totransmitter330 in this alternative embodiment results in a tension force rather than a peeling force being applied totape320′, inhibiting inadvertent removal until an edge oftape320′ is intentionally peeled up. Preferably, single-sided portion438 has a width roughly double the width of double-sided portion436. In the preferred embodiment, theses widths are 2.14 and 1.14 inches, respectively. Preferably, the length that single-sided portion438 extends beyond double-sided portion436 is roughly equivalent to the combined height oftransmitter330 attached to mount312, in this case about 0.5 inches.
• In the preferred embodiment,sensor314 is made from a 0.005 inch thick Mylar substrate, such as Dupont Melinex ST-505, print treated both sides, heat stabilized and bi-axially oriented.Main surface346 is 0.315 tall by 0.512 wide, andorthogonal surface356 is 0.374 wide by 0.202 deep.Sensor tail431 is 0.230 long by 0.023 wide.Semispherical sensor dimple350 is 0.050 inches wide and 0.026 inches deep.Introducer340 is made from SUS 301 medical grade stainless steel, 0.004 inches thick, having a surface roughness less than or equal to 0.5 micrometers. The height of the main portion ofintroducer340 is 0.614 inches, and the inside width is 0.513 inches. The overall thickness of rolledrails348 is 0.026 inches. The length and width ofintroducer tail424 are 0.354 and 0.036 inches, respectively. The preferred angle of the sharp340 is 21 degrees. Preferably,semispherical introducer dimple352 has a radius of 0.024 inches. In the preferred embodiment,shuttle338 has an average speed of at least 1 meter/second, and has a momentum at its end of travel of about 2.65 lb-m/sec.
• Preferably,housing334,button324,shuttle338,base344 and mount312 are all injection molded from G.E. Lexan PC. Inside and outside working surfaces ofarms378 onbutton324 are preferably lubricated withDow Corning 360 Medical Fluid.Drive spring336 has a free length of 1.25 inches, a working length of 1.00 inch, and a rate between 20 and 30 pounds per inch.Retraction spring342 has a free length of 1.5 inches, a working length of 0.35 inches, and a rate between 0.15 and 0.35 pounds per inch.Adhesive tape320 preferably is medical grade acrylic adhesive on polyester film (such as Acutek 0396013) with a semi-bleached kraft liner having silicon release.
• Referring toFIG. 29, aninterconnect440 is shown for providing waterproof electrical connections betweensensor314 andtransmitter330.Interconnect440 includes aseal442 mounted on an end oftransmitter330 that contacts one side ofsensor314 whentransmitter330 is slid ontomount312. Whentransmitter330 is locked into place onmount312,seal442 is compressed betweentransmitter330 andsensor314 and urgessensor314 against raisedend stop444 ofmount312.
• Referring toFIG. 30, further details ofinterconnect440 are shown.Seal442 has anexterior wall446 for surrounding electrical contacts448 (in this case four), andinterior walls450 for isolatingelectrical contacts448 from each other.Rim452 formed on thetransmitter housing330 surrounds thebase454 ofseal442 to prevent it from collapsing outward when compressed.
• Referring toFIG. 31, an enlarged partial view ofFIG. 30 is shown withseal442 and one spring removed for clarity.Electrical contacts448 are preferably constructed from compression springs456 mounted on connector lugs458.Lugs458 are stamped rearward on their edges to form protrusions460 that retain springs456. Alternately or in conjunction with this stamping, plastic rings (not shown) can be melted over the base of eachspring456 for attaching it to itsrespective lug458. Connector lugs458 can protrude through slots intransmitter housing330, or be insert molded integral with theplastic housing330 when it is molded.
• Referring toFIG. 32, and enlarged perspective view of theseal442 is shown. It has been discovered through experimentation that twolips462 of equal height along the distal edge ofexterior wall446 provide the best seal from exterior elements. Good isolation betweenelectrical contacts448 is best achieved by havinginterior walls450 with a height equal to that oflips462.Recesses464 should be sized large enough so thatseal442 does not interfere with the movement ofsprings456 whenseal442 and springs456 are compressed. In the preferred embodiment, the distal face ofseal442 defined bylips462 is formed at a 1 degree angle to match the draft angle ofmount end stop444.
• Seal442 is preferably made of shore A 30 durometer compression molded silicone. It is envisioned thatseal442 can be shortened in the axial direction (parallel to springs456) to reduce the force required to compress it when attachingtransmitter330 to mount312. Best results forfastening seal442 totransmitter housing330 have been achieved with double sidedadhesive tape320, silicone adhesive on one side and acrylic adhesive on the other for sticking to the PC-ABS blend of thetransmitter housing330, such as product number 9731 manufactured by 3M Company of St. Paul, Minn.Springs456 are preferably made from gold-plated beryllium copper so as to deter galvanic current effects. Preferably,main surface346 ofsensor314 that contacts seal442 has a uniform thickness dielectric coating with a window in it (i.e. no dielectric) wheresprings456contact sensor314. Aninterconnect440 constructed as described above remains water proof when submerged to a depth of at least 1 meter for 45 minutes.
• To increase the reliability of sensor insertion, the following enhancements can be added to theinserter kit300 described above. First, a sensor flap466, as shown inFIG. 25, can be formed along the top edge ofsensor314. Whensensor314 reaches the extended, delivered position as shown inFIG. 23, flap466 catches on bottom edge468 ofbase344, shown inFIG. 19, to ensure thatsensor314 separates fromintroducer340 asshuttle338 returns upward to the retracted position. Adhesive can also be located on the bottom oforthogonal sensor surface356 to ensure thatsensor314 adheres to thesensor contact portion428 on the top ofadhesive mount tape320, as shown inFIG. 16.
• Referring toFIGS. 33A and 33B,actuator button324′ can be made easier for elderly patients to push by anchoring the upper end ofdrive spring336 on ahousing bridge470 instead ofbutton324. This change also makes the insertion force ofinserter310 more consistent, and allows stronger spring forces to be used if desired.Bridge470 spans across opening376′ and divides it into twoopenings472 in the top ofhousing334′. The top portion ofbutton324′ is bifurcated into twoprotrusions474 that each extend through anopening472. A clearance hole (not shown) is provided through the center ofbutton324′ to allowdrive spring336 to pass through and secure around a post (not shown) depending from the bottom center ofbridge470.
• Safety lock key476 can be provided to preventactuator button324′ from being pressed untilkey476 is removed.Aperture478 is provided in the top center ofbridge470 for receivingboss480 located at the bottom ofkey476, thereby allowing key476 to rotate. Whenkey handle482 is rotated perpendicular tobutton protrusions474 as shown, two opposingperpendicular fins484 onkey476 swing into inwardly facing slots (not shown) on the inside ofprotrusions474 and preventbutton324′ from being actuated. Whenkey handle482 andfins484 are rotated parallel tobutton protrusions474 such thatfins484 disengage therefrom, key476 can be removed andbutton324′ can then be actuated. Other than these modifications, thisinserter kit300′ functions the same as the embodiment previous described.
• To provide an easier and more consistent release ofshuttle338 byactuator button324 or324′, it is envisioned that less aggressive finger engagement withstops386 can be employed, or the above designs can be modified to have a single, more centrally located shuttle release finger (not shown) instead of the twooutboard fingers412 shown.
• The present invention should not be considered limited to the particular examples described above. Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable and which fall within the general scope of the invention will be readily apparent to those of skill in the art to which the present invention is directed upon review of the instant specification.

Claims (16)

1. (canceled)

2. An insertion kit, comprising:

a sensor and an introducer needle, wherein the sensor and the introducer needle are configured and arranged with a shape, such that the sensor is retained in the introducer needle by a friction fit such that motion of the sensor with respect to the introducer needle is minimized prior to sensor insertion; and

an applicator configured to cause the needle to be inserted through a skin of a host, wherein the applicator is further configured to position at least a portion of the sensor in contact with a biological fluid of the host.

3. The kit ofclaim 2 wherein the sensor is retained in a lumen of the introducer needle.

4. The kit ofclaim 3 wherein the sensor is retained within the lumen.

5. The kit ofclaim 2 wherein the sensor is retained within the introducer needle.

6. The kit ofclaim 2 wherein the sensor is retained in the introducer needle by the friction fit of a contact point between the sensor and the introducer needle.

7. The kit ofclaim 2 wherein the motion is longitudinal motion.

8. The insertion kit ofclaim 2, wherein the applicator is further configured to substantially completely withdraw the introducer needle from the host after the sensor is transcutaneously positioned in fluid contact with the biological fluid of the host.

9. The insertion kit ofclaim 2, wherein the applicator includes a spring biased mechanism.

10. The insertion kit ofclaim 2, wherein the shape is a bend.

11. An insertion kit, comprising:

a sensor and an introducer needle, wherein the sensor and the introducer needle are configured and arranged with a shape, such that the sensor is retained within a lumen of the introducer needle by a friction fit of multiple contact points separated by non-contact points between the sensor and the lumen of the introducer needle, such that longitudinal motion of the sensor with respect to the introducer needle is minimized prior to sensor insertion; and

an applicator configured to cause the needle to be inserted through a skin of a host, wherein the applicator is further configured to position at least a portion of the sensor in contact with a biological fluid of the host.

12. An analyte sensor system, comprising:

an analyte sensor and an applicator comprising an introducer needle, wherein the applicator is configured to position at least a portion of the sensor in contact with a biological fluid of a host by insertion of, and subsequent withdrawal of, the introducer needle through the skin of the host, wherein the analyte sensor is configured and arranged to be held by a friction fit of the surface of the sensor with the introducer needle in order to maintain the sensor longitudinally within the introducer needle prior to withdrawal of the introducer needle from the host and minimize motion of the sensor during withdrawal of the introducer needle from the host.

13. The system ofclaim 12 wherein the analyte sensor is configured and arranged to be held by the friction fit of the surface of the sensor with an inner lumen of the introducer needle.

14. The sensor ofclaim 12, wherein the sensor has a slight bend when the sensor is held within the introducer needle.

15. A method, comprising the steps of:

longitudinally maintaining an analyte sensor in a first configuration of the sensor within an introducer needle during insertion of the introducer needle into a host, wherein the first configuration uses a frictional force caused by the shape of the sensor against a surface of the introducer needle to maintain the sensor within the introducer needle; and

withdrawing the introducer needle from the host, wherein the step of withdrawing comprises releasing the sensor from the first configuration to a second configuration of the sensor that is different from the first configuration after release of the sensor from the introducer needle.

16. The method ofclaim 15, wherein the step of withdrawing comprises positioning the sensor to be in fluid contact with a biological fluid of a host.

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