(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2004/0133164 A1
`(43) Pub. Date:
`Jul. 8, 2004
`Funderburk et al.
`
`US 2004O1331.64A1
`
`(54) SENSOR INSERTER DEVICE AND
`METHODS OF USE
`
`(76) Inventors: Jeffery V. Funderburk, Fremont, CA
`(US); Duane O. Yamasaki, El Cerrito,
`CA (US); Brian Van Hiel, Marietta, GA
`(US); Stephen J. Flynn, Peachtree City,
`GA (US); Bradley D. Kelemen,
`Longmont, CO (US)
`Correspondence Address:
`PARSONS HSUE & DE RUNTZ, LLP
`SUTE1800
`655 MONTGOMERY STREET
`SAN FRANCISCO, CA 94111 (US)
`(21) Appl. No.:
`10/703,214
`(22) Filed:
`Nov. 5, 2003
`Related U.S. Application Data
`(60) Provisional application No. 60/424,099, filed on Nov.
`5, 2002.
`
`
`
`Publication Classification
`
`(51) Int. Cl." ...................................................... A61M 5/20
`(52) U.S. Cl. .............................................................. 604/134
`
`(57)
`
`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.
`
`Page 1 of 39
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`Patent Application Publication
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`Jul. 8, 2004 Sheet 1 of 27
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`US 2004/0133164 A1
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`40
`
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`SMALL RECEIVER
`AND
`DISPLAY UNIT
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`CONTROL
`UNIT
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`FIG. 1
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`Patent Application Publication Jul. 8, 2004 Sheet 2 of 27
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`57
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`Patent Application Publication Jul. 8, 2004 Sheet 3 of 27
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`US 2004/0133164 A1
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`Patent Application Publication Jul. 8, 2004 Sheet 4 of 27
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`US 2004/0133164 A1
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`Patent Application Publication Jul. 8, 2004 Sheet 5 of 27
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`Patent Application Publication Jul. 8, 2004 Sheet 6 of 27
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`Patent Application Publication Jul. 8, 2004 Sheet 7 of 27
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`Patent Application Publication Jul. 8, 2004 Sheet 8 of 27
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`Patent Application Publication Jul. 8, 2004 Sheet 9 of 27
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`Patent Application Publication Jul. 8, 2004 Sheet 10 of 27
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`Patent Application Publication Jul. 8, 2004 Sheet 11 of 27
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`US 2004/0133164 A1
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`Patent Application Publication Jul. 8, 2004 Sheet 12 of 27
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`Jul. 8,2004 Sheet 14 of 27
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`Patent Application Publication Jul. 8, 2004 Sheet 15 of 27
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`Patent Application Publication Jul. 8, 2004 Sheet 16 of 27
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`US 2004/0133164 A1
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`Patent Application Publication Jul. 8, 2004 Sheet 17 of 27
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`Patent Application Publication Jul. 8, 2004 Sheet 18 of 27
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`Patent Application Publication Jul. 8, 2004
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`Patent Application Publication Jul. 8, 2004
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`Patent Application Publication Jul. 8, 2004 Sheet 22 of 27
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`Patent Application Publication Jul. 8, 2004 Sheet 23 of 27
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`Patent Application Publication Jul. 8, 2004 Sheet 24 of 27
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`Patent Application Publication Jul. 8, 2004 Sheet 25 of 27
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`Patent Application Publication
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`US 2004/0133164 Al
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`FIG._33A
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`Page 27 of 39
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`Page 27 of 39
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`Patent Application Publication Jul. 8, 2004 Sheet 27 of 27
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`US 2004/0133164 A1
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`FIG.33B
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`Page 28 of 39
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`

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`US 2004/O133164 A1
`
`Jul. 8, 2004
`
`SENSOR INSERTER DEVICE AND METHODS OF
`USE
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`0001. 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
`0002 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 electro
`chemical Sensor in a patient for Such monitoring.
`
`BACKGROUND OF THE INVENTION
`0003. 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 individu
`als 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.
`0004. 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 calorimetric, 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 indi
`viduals to more easily monitor their glucose, or other
`analyte, levels.
`0005) 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 num
`bers. 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 doctors office, unless the patient is restricted in his
`activities.
`
`0006 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 activi
`ties 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 hypogly
`cemia. The patient can then take appropriate actions.
`SUMMARY OF THE INVENTION
`0007 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 hous
`ing is also adapted to receive a portion of an electrochemical
`Sensor. The Sensor control unit includes two or more con
`ductive 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 refer
`ence electrode, and a temperature probe. The analyte moni
`toring 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 moni
`toring System or a component of the analyte monitoring
`System may optionally include a processor capable of deter
`mining a drug or treatment protocol and/or a drug delivery
`System.
`0008 According to one aspect of the invention, an inser
`tion kit is disclosed for inserting an electrochemical Sensor
`
`Page 29 of 39
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`US 2004/O133164 A1
`
`Jul. 8, 2004
`
`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 elec
`trochemical Sensor. The insertion kit also includes an inser
`tion gun having a port configured to accept the electrochemi
`cal 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.
`0009. 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.
`0.010 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
`0.011 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:
`0012 FIG. 1 is a block diagram of one embodiment of a
`Subcutaneous analyte monitor using a Subcutaneously
`implantable analyte Sensor, according to the invention.
`0013 FIG. 2 is a top view of one embodiment of an
`analyte Sensor, according to the invention.
`0.014
`FIG. 3 is an expanded side view of one embodi
`ment of a Sensor and an introducer, according to the inven
`tion.
`0015 FIGS. 4A, 4B, 4C are cross-sectional views of
`three embodiments of the introducer of FIG. 3.
`0016 FIG. 5 is a cross-sectional view of one embodi
`ment of a on-skin Sensor control unit, according to the
`invention.
`0017 FIG. 6 is a top view of a base of the on-skin sensor
`control unit of FIG. 5.
`0018 FIG. 7 is a bottom view of a cover of the on-skin
`sensor control unit of FIG. 5.
`0.019
`FIG. 8 is a perspective view of the on-skin sensor
`control unit of FIG. 5 on the skin of a patient.
`0020 FIG. 9 is a perspective view of the internal struc
`ture of an insertion gun, according to the invention.
`0021 FIG. 10A is a top view of one embodiment of an
`on-skin Sensor control unit, according to the invention.
`
`0022 FIG. 10B is a top view of one embodiment of a
`mounting unit of the on-skin sensor control unit of FIG.
`10A.
`0023 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.
`0024 FIG. 11B is a top view of one embodiment of a
`mounting unit of the on-skin sensor control unit of FIG.
`11A.
`0025 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 of FIG. 11A.
`0026 FIG. 11D is a bottom view of the housing of FIG.
`11C.
`0027 FIG. 11E is a top view of the on-skin sensor
`control unit of FIG. 11A with a cover of the housing
`removed.
`0028 FIG. 12 depicts an introducer, sensor, insertion gun
`and mounting unit, which can be assembled and Sold
`together in an insertion kit.
`0029 FIG. 13 is a perspective view showing a preferred
`commercial embodiment of a Sensor inserter and adhesive
`mount constructed according to the invention.
`0030 FIG. 14 is a perspective view of the adhesive
`mount and sensor attached to the patient’s skin.
`0031 FIG. 15 is a perspective view of the transmitter
`attached to the adhesive mount.
`0032 FIG. 16 is an exploded perspective view of the
`preferred commercial embodiment of FIG. 13.
`0033 FIG. 17 is a side elevation view of the preferred
`commercial embodiment of FIG. 13.
`0034 FIG. 18 is an end elevation view of the preferred
`commercial embodiment of FIG. 13.
`0035 FIG. 19 is a cross-sectional view taken along line
`19-19 in FIG. 18.
`0036 FIG. 20 is a cross-sectional view taken along line
`20-2O in FIG. 17.
`0037 FIG. 21 is a broken away view similar to FIG.20,
`showing the Shuttle in the neutral position.
`0038 FIG.22 is a broken away view similar to FIG.20,
`showing the Shuttle in the cocked position.
`0039 FIG. 23 is a broken away view similar to FIG.20,
`showing the Shuttle in the insertion position.
`0040 FIG. 24 is a cross-sectional view taken along line
`24-24 in FIG. 17.
`0041 FIG.25 is a perspective view of a transcutaneously
`implantable Sensor.
`0042 FIG. 26A is a perspective view of a sensor intro
`ducer.
`0043 FIG. 26B is a bottom view of the introducer shown
`in FIG. 26A.
`0044 FIG. 27 is a perspective view of a shuttle member.
`
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`Jul. 8, 2004
`
`004.5 FIG.28 is a top plan view of an oversized adhesive
`tape.
`0046 FIG. 29 is a perspective view of the transmitter
`attached to the adhesive mount and showing the Sensor
`Sandwiched therebetween.
`0047 FIG. 30 is a perspective view of the interconnect
`on one end of the transmitter.
`0.048
`FIG. 31 is an enlarged perspective view of the
`interconnect of FIG. 30 with the seal and one spring
`removed for clarity.
`0049 FIG. 32 is an enlarged perspective view of the
`interconnect Seal.
`0050 FIG. 33A is a perspective view of an alternative
`embodiment of a Sensor inserter kit.
`0051 FIG. 33B is an exploded view of some of the
`components shown assembled in FIG. 33A.
`0.052 While the invention is amenable to various modi
`fications 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
`0053. 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 moni
`toring the level of the analyte over a time period which may
`range from days to weeks or longer.
`0.054 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 ana
`lyte 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. Subcu
`taneous 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.
`0055 One embodiment of the analyte monitoring system
`40 for use with an implantable sensor 42, and particularly for
`use with a Subcutaneously implantable Sensor, is illustrated
`in block diagram form in FIG. 1. The analyte monitoring
`System 40 includes, at minimum, a Sensor 42, a portion of
`which is configured for implantation (e.g., Subcutaneous,
`venous, or arterial implantation) into a patient, and a Sensor
`control unit 44. The sensor 42 is coupled to the sensor
`control unit 44 which is typically attached to the skin of a
`patient. The Sensor control unit 44 operates the Sensor 42,
`including, for example, providing a Voltage acroSS the
`electrodes of the Sensor 42 and collecting Signals from the
`sensor 42. The sensor control unit 44 may evaluate the
`Signals from the Sensor 42 and/or transmit the Signals to one
`or more optional receiver/display units 46, 48 for evaluation.
`The sensor control unit 44 and/or the receiver/display units
`46, 48 may display or otherwise communicate the current
`level of the analyte. Furthermore, the sensor control unit 44
`and/or the receiver/display units 46, 48 may indicate to the
`patient, Via, for example, an audible, Visual, or other Sen
`Sory-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 hypogly
`cemia or hyperglycemia.
`0056. A sensor 42 includes at least one working electrode
`58 formed on a Substrate 50, as shown in FIG. 2. The sensor
`42 may also include at least one counter electrode 60 (or
`counter/reference electrode) and/or at least one reference
`electrode 62. The substrate 50 of the sensor may be formed
`using a variety of non-conducting materials, including, for
`example, polymeric or plastic materials and ceramic mate
`rials. Suitable materials for a particular Sensor 42 may be
`determined, at least in part, based on the desired use of the
`Sensor 42 and properties of the materials.
`0057. In some embodiments, the Substrate is flexible. For
`example, if the Sensor 42 is configured for implantation into
`a patient, then the Sensor 42 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 the Sensor 42. A
`flexible Substrate 50 often increases the patient’s comfort
`and allows a wider range of activities. Suitable materials for
`a flexible Substrate 50 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 polycar
`bonates, polyesters (e.g., Mylar' and polyethylene tereph
`thalate (PET)), polyvinyl chloride (PVC), polyurethanes,
`polyethers, polyamides, polyimides, or copolymers of these
`thermoplastics, such as PETG (glycol-modified polyethyl
`ene terephthalate).
`0058. In other embodiments, the sensors 42 are made
`using a relatively rigid Substrate 50 to, for example, provide
`Structural Support against bending or breaking. Examples of
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`rigid materials that may be used as the substrate 50 include
`poorly conducting ceramics, Such as aluminum oxide and
`Silicon dioxide. One advantage of an implantable Sensor 42
`having a rigid Substrate is that the Sensor 42 may have a
`Sharp point and/or a sharp edge to aid in implantation of a
`Sensor 42 without an additional introducer.
`0059. It will be appreciated that for many sensors 42 and
`Sensor applications, both rigid and flexible Sensors will
`operate adequately. The flexibility of the Sensor 42 may also
`be controlled and varied along a continuum by changing, for
`example, the composition and/or thickness of the Substrate
`50.
`0060. In addition to considerations regarding flexibility, it
`is often desirable that implantable sensors 42 should have a
`substrate 50 which is non-toxic. Preferably, the Substrate 50
`is approved by one or more appropriate governmental agen
`cies or private groups for in Vivo use.
`0061 Although the substrate 50 in at least some embodi
`ments has uniform dimensions along the entire length of the
`sensor 42, in other embodiments, the Substrate 50 has a distal
`end 67 and a proximal end 65 with different widths 53, 55,
`respectively, as illustrated in FIG. 2. In these embodiments,
`the distal end 67 of the substrate 50 may have a relatively
`narrow width 53. For sensors 42 which are implantable into
`the Subcutaneous tissue or another portion of a patient's
`body, the narrow width 53 of the distal end 67 of the
`substrate 50 may facilitate the implantation of the sensor 42.
`Often, the narrower the width of the sensor 42, the less pain
`the patient will feel during implantation of the Sensor and
`afterwards. The Sensor 42 is designed to be a replaceable
`component in an implantable analyte monitor. Typically, the
`Sensor 42 is capable of operation over a period of dayS.
`Preferably, the period of operation is at least three days. The
`Sensor 42 can then be removed and replaced with a new
`SCSO.
`0.062 An introducer 120 can be used to subcutaneously
`insert the sensor 42 into the patient, as illustrated in FIG. 3.
`The introducer 120 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, the intro
`ducer 120 is pointed and/or sharp at the tip 121 to facilitate
`penetration of the skin of the patient. Asharp, thin introducer
`may reduce pain felt by the patient upon insertion of the
`sensor 42. In other embodiments, the tip 121 of the intro
`ducer 120 has other shapes, including a blunt or flat shape.
`These embodiments may be particularly useful when the
`introducer 120 does not penetrate the skin but rather serves
`as a structural Support for the Sensor 42 as the Sensor 42 is
`pushed into the skin.
`0.063. The introducer 120 may have a variety of cross
`sectional shapes, as shown in FIGS. 4A, 4B, and 4C. The
`introducer 120 illustrated in FIG. 4A is a flat, planar, pointed
`Strip of rigid material which may be attached or otherwise
`coupled to the Sensor 42 to ease insertion of the Sensor 42
`into the Skin of the patient, as well as to provide Structural
`Support to the Sensor 42 during insertion. The introducers
`120 of FIGS. 4B and 4C are U- or V-shaped implements
`that Support the Sensor 42 to limit the amount that the Sensor
`42 may bend or bow during insertion. The cross-sectional
`width 124 of the introducers 120 illustrated in FIGS. 4B and
`4C is typically 1 mm or less, preferably 700 um or less, more
`
`preferably 500 um or less, and most preferably 300 um or
`less. The cross-sectional height 126 of the introducer 120
`illustrated in FIGS. 4B and 4C is typically about 1 mm or
`less, preferably about 700 um or less, and more preferably
`about 500 um or less.
`0064. The sensor 42 itself may include optional features
`to facilitate insertion. For example, the Sensor 42 may be
`pointed at the tip 123 to ease insertion, as illustrated in FIG.
`3. In addition, the sensor 42 may include a barb 125 which
`helps retain the Sensor 42 in the Subcutaneous tissue of the
`patient. The barb 125 may also assist in anchoring the Sensor
`42 within the Subcutaneous tissue of the patient during
`operation of the sensor 42. However, the barb 125 is
`typically Small enough that little damage is caused to the
`Subcutaneous tissue when the Sensor 42 is removed for
`replacement. The sensor 42 may also include a notch 127
`that can be used in cooperation with a corresponding Struc
`ture (not shown) in the introducer to apply pressure against
`the Sensor 42 during insertion, but disengage as the intro
`ducer 120 is removed. One example of such a structure in the
`insertion device is a rod (not shown) between two opposing
`Sides of an introducer 120 and at an appropriate height of the
`introducer 120.
`0065. In operation, the sensor 42 is placed within or next
`to the introducer 120 and then a force is provided against the
`introducer 120 and/or sensor 42 to carry the sensor 42 into
`the Skin of the patient. In one embodiment, the force is
`applied to the Sensor 42 to push the Sensor into the skin,
`while the introducer 120 remains stationary and provides
`Structural Support to the Sensor 42. Alternatively, the force is
`applied to the introducer 120 and optionally to the sensor 42
`to push a portion of both the sensor 42 and the introducer
`120 through the skin of the patient and into the subcutaneous
`tissue. The introducer 120 is optionally pulled out of the skin
`and Subcutaneous tissue with the Sensor 42 remaining in the
`Subcutaneous tissue due to frictional forces between the
`Sensor 42 and the patient's tissue. If the Sensor 42 includes
`the optional barb 125, then this structure may also facilitate
`the retention of the sensor 42 within the interstitial tissue as
`the barb catches in the tissue.
`0066. The force applied to the introducer 120 and/or the
`Sensor 42 may be applied manually or mechanically. Pref
`erably, the Sensor 42 is reproducibly inserted through the
`skin of the patient. In one embodiment, an insertion gun is
`used to insert the Sensor. One example of an insertion gun
`200 for inserting a sensor 42 is shown in FIG. 9. The
`insertion gun 200 includes a housing 202 and a carrier 204.
`The introducer 120 is typically mounted on the carrier 204
`and the sensor 42 is pre-loaded into the introducer 120. The
`carrier 204 drives the sensor 42 and, optionally, the intro
`ducer 120 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 the insertion gun 200. In Some instances, for example,
`when using a Spring, the carrier 204 and introducer 120 may
`be moved, cocked, or otherwise prepared to be directed
`towards the skin of the patient.
`0067. After the sensor 42 is inserted, the insertion gun
`200 may contain a mechanism which pulls the introducer
`120 out of the skin of the patient. Such a mechanism may use
`a Spring, electromagnet, or the like to remove the introducer
`120.
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`0068 The insertion gun may be reusable. The introducer
`120 is often disposable to avoid the possibility of contami
`nation. Alternatively, the introducer 120 may be sterilized
`and reused. In addition, the introducer 120 and/or the sensor
`42 may be coated with an anticlotting agent to prevent
`fouling of the Sensor 42.
`0069. In one embodiment, the sensor 42 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.
`0070 Although the sensor 42 may be inserted anywhere
`in the body, it is often desirable that the insertion site be
`positioned So that the on-skin Sensor control unit 44 can be
`concealed. In addition, it is often desirable that the insertion
`site be at a place on the b