Body fluid sampler

A sampling apparatus for sampling body fluid includes a sampler having an external geometry selected to mate with an internal geometry of a testing apparatus such that the sampler may be inserted within the testing apparatus in a predetermined alignment—and with a sampling location positioned accurately within a light path for detecting an amount of a desired constituent within fluid collected by the sampler.

II. BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to an apparatus for testing body fluid constituents. More particularly, this invention pertains to a sampler for use in collecting body fluids such as interstitial fluid.

2. Description of the Prior Art

In the prior art, there are numerous examples of apparatus for testing and determining the level of constituents in human blood. A great deal of attention has been directed to the development of techniques and apparatus for measuring blood glucose.

As noted in commonly assigned and co-pending U.S. patent application Ser. Nos. 08/321,305 and 08/136,304 (corresponding to PCT International Publication No. WO95/10223 published Apr. 20, 1995 on International Application No. PCT/US94/11580 and incorporated herein by reference), the determination of the level of a constituent of blood can be achieved by measuring the level of that constituent in other body fluids such as interstitial fluid. The aforementioned patent applications and international publication disclose a method and apparatus for a minimally invasive technique for collecting a sample of interstitial fluid through use of an extremely small needle which penetrates into the dermal layer of the skin in order to collect a low blood or blood-free sample of interstitial fluid. The collected interstitial fluid can then be analyzed for a determination of the level of constituents within the fluid. For example, the collected interstitial fluid can be analyzed for an amount of glucose with the determined amount being representative of the amount of glucose contained within the patient's blood.

The aforementioned applications and international publication disclose the use of a ring (item60inFIG. 6of the application) which surrounds the needle to create a pressure area on the patient's skin. It is believed this leads to an increase in the amount of interstitial fluid being collected.

In the collection of interstitial fluid, it is desirable to increase the speed at which a sample is collected. In the absence of mechanical or other assistance, the rate at which interstitial fluid is collected through a small diameter tube or needle is very slow. Preferably, patients utilizing such equipment for home use will be provided with a system which collects interstitial fluid at a rapid pace to ensure that a patient does not remove the needle too early in its application. Also, it is important to provide for techniques to increase a volume of interstitial fluid being collected through a needle.

When collecting any body fluid through use of a needle, it is important that the needle be a disposable item in order to prevent re-use of the needle. Such re-use can result in the transmission of disease. Where the apparatus is to be used in a patient's home by the patient, the apparatus should be simple to use and with the needle incorporated in a disposable item. Since the needle is incorporated in a disposable item, it is important that the disposable item be amenable to low-cost manufacture. Also, in order to test the interstitial fluid, the interstitial fluid collection mechanism must be coupled with an analytic mechanism for analyzing the collected fluid. Where such a device is to be used in home by low-skilled patients, it is important that the sampler and the analytic portion of the device be mutually configured to ensure that the sampler is coupled to the apparatus in a repeatable and reliable manner to minimize errors resulting from use of the apparatus by untrained patients.

III. SUMMARY OF THE INVENTION

According to a preferred embodiment of the present invention, a sampler is disclosed for use in a body fluid collection apparatus where the collection apparatus has a light source for generating a testing light and a light detector for detecting light. The light source and the detector are contained within the apparatus in a predetermined alignment to define a light path between the source and the detector. The apparatus further includes an opening of predetermined geometry to define an access to the light path. The sampler includes a main body having a handle and a sample end. The sample end has an external mating geometry which mates with the predetermined geometry of the opening of the apparatus. Therefore, the sample end can be inserted into the opening in a predetermined alignment such that the sampler may be repeatably inserted within the opening in the predetermined alignment with a sample location of the sample end positioned within the light path. A body fluid collection apparatus is carried on the sampler. The body fluid collection apparatus includes a needle sized to protrude beyond the housing. The needle protrudes a distance selected for the needle to penetrate into a body fluid-laden skin layer when the housing is urged against the skin layer by the user. An absorbent medium is carried on the sampler in fluid flow communication with the needle for body fluid to flow from the needle onto the medium. The medium is positioned at the sample location.

IV. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1is a cross-sectional elevation view of an interstitial fluid apparatus showing a sampler contained within the apparatus in a retracted position;

FIG. 2is the view ofFIG. 1with the apparatus shown in an extended position;

FIG. 3is a perspective exploded view of the apparatus ofFIG. 1;

FIG. 4is the view ofFIG. 3rotated 90° to the right of the view ofFIG. 3;

FIG. 7is a perspective view of an optics housing for use in the apparatus ofFIG. 1;

FIG. 8is a side elevation view of the housing ofFIG. 7;

FIG. 8Ais an enlarged view of a bottom portion of the view ofFIG. 8;

FIG. 9is a side elevation view of the housing ofFIG. 7rotated 90° from the vies ofFIG. 8;

FIG. 11is a bottom plan view of the housing ofFIG. 7;

FIG. 12is a perspective view of a shell for use in the apparatus ofFIG. 1;

FIG. 13is a sectional view of the shell ofFIG. 12;

FIG. 14is a perspective view of a collar for use in the apparatus ofFIG. 1;

FIG. 15is a sectional view of the collar ofFIG. 14;

FIG. 16is a perspective view of a base for use in the apparatus ofFIG. 1;

FIG. 17is a sectional view of the base ofFIG. 16;

FIG. 18is a top, left side and rear end exploded perspective view of a sampler for use in the apparatus ofFIG. 1;

FIG. 19is a top, left side and rear end perspective view of a sampler main body for the sampler ofFIG. 18;

FIG. 20is a left side elevation view of the sampler main body ofFIG. 18(with the opposite side being substantially identical);

FIG. 23is an enlarged bottom view of a front portion of the main body ofFIG. 20;

FIG. 24is a side elevation view of a piston for the sampler ofFIG. 18;

FIG. 26is a side elevation view of a catch pin for the sampler ofFIG. 18;

FIG. 28is a schematic representation showing the apparatus ofFIG. 1placed against a patient's skin;

FIG. 29is the view ofFIG. 28showing initial forcing of the apparatus against the patient's skin;

FIG. 30is the view ofFIG. 28showing urging of the apparatus against the, patient's skin with penetration of a needle into the patient's skin layer and with a piston aligned with a pressure ring;

FIG. 31is the view ofFIG. 28with the piston protruding beyond the pressure ring;

FIG. 32is a top, front, right side perspective view of an alternative embodiment of the present invention;

FIG. 33is an exploded view of the alternative embodiment ofFIG. 32;

FIG. 34is a cross-sectional view of the embodiment ofFIG. 32;

FIG. 35is a transverse cross-sectional view of the embodiment ofFIG. 32;

FIG. 36is a partial sectional view of the embodiment ofFIG. 32showing initial insertion of a sampler into the apparatus;

FIG. 37is the view ofFIG. 36showing further insertion of the sampler into the apparatus for a cam to engage a cam follower;

FIG. 38is the view ofFIG. 37showing still further insertion of the sampler with a sample end pivoted to a sample position and with the sampler not yet fully inserted;

FIG. 39is the view ofFIG. 38with the sampler fully inserted;

FIG. 40is the view ofFIG. 39with the sampler partially withdrawn and with the sample end partially pivoted to a storage position by reason of the cam acting against a second cam follower;

FIG. 41is an enlarged view of relative positioning of a needle on a sampler with a membrane not shown;

FIG. 42is a perspective view of a needle and membrane assembly; and

V. DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to the various drawing figures in which identical elements are numbered identically throughout, a description of the preferred embodiment of the present invention will be shown. While the invention will be described with reference to an apparatus for collecting interstitial fluid to test for glucose within the interstitial fluid, it will be appreciated that the apparatus can be used for testing any body constituent which may be contained within interstitial fluid.

In a preferred embodiment, the apparatus is disclosed with reference to use of a penetrating needle and an absorbing membrane such as that shown and described in U.S. patent application Ser. Nos. 08/321,305 and 08/136,304 (and corresponding PCT International Publication No. WP 95/10223, dated Apr. 20, 1995 on International Application No. PCT/US94/11580, incorporated herein by reference). With reference toFIGS. 16–20of that application (showing a representative embodiment of the invention shown in that application), a needle214′ is surrounded and maintained in fixed relative position by a ring202′. The ring is placed against a patient's skin in order to define a pressurized area on the patient's skin as the needle214′ penetrates into the skin. The needle is sized to be about 28 to 32 gauge (i.e., 0.36 mm outside diameter to 0.23 mm outside diameter) with an anticipated preferred size of about 30 gauge. The needle is made as small as possible to provide a minimally intrusive and painless insertion into the skin. The needle is sized to penetrate into the dermis for a variety of reasons as best disclosed in the aforementioned application including low pain and the collection of low blood interstitial fluid for subsequent testing. An absorbent membrane210′ is placed in fluid flow communication with the needle214′ such that interstitial fluid which flows through the needle214′ is deposited on the membrane210′ as a spot available for subsequent testing with light (visible or non-visible spectrum). The amount of absorption of various wavelengths of the light indicates the concentration of constituents for testing such as glucose or the like.

The present invention pertains to a testing apparatus which includes a needle10disposed in fluid flow communication with an absorbent membrane12both in accordance with the teachings of the aforementioned PCT International Publication No. WO95/10223.

A. First Described Embodiment

The present invention is directed to an apparatus1–6) for collecting and testing interstitial fluid. The apparatus20includes a main housing22(shown inFIGS. 1 and 2only) coupled to a base24. The apparatus20further includes a collar26secured to the base24. A shell28is contained within the collar26. An optics housing30is contained within the shell28. Finally, a sampler32is provided to be received within the optics housing30. Each of base24, collar26, shell28, optics housing30and sampler32will be separately described.

Main housing22is shown only in section inFIGS. 1 and 2. Main housing22is sized to be gripped by a patient such that the apparatus20may be urged against the patient's skin for purpose of collecting interstitial fluid as will be described. In addition to constituting a handle which can be grasped by the patient, the main housing22will contain electronics and the like for generating power for a light source as will be-described and for analyzing signals from a light detector (as will be described) in order to calculate the level of constituents, such as blood glucose, contained within a sample of interstitial fluid. Such electronics are not shown but it will be appreciated that such electronics are well within the skill of the art. Examples of circuits for analyzing sampling light are described in commonly assigned U.S. Pat. No. 5,115,133 to Knudson dated May 19, 1992 and the aforementioned International Publication No. WO95/10223.

The base24is separately shown inFIGS. 16 and 17. Base24is substantially cylindrical and is provided with an end plate36having holes38extending at least partially therethrough with the holes38sized to receive any suitable fastening means such as bolts or the like for fastening of the end plate36to the main housing22. The base24further includes an inner hollow cylinder40extending from plate36with the inner cylinder40being coaxial with an outer cylinder42of the base24. Outer cylinder42has a threaded inner surface44.

The collar26is separately shown inFIGS. 14 and 15. The collar26includes an enlarged cylindrical portion50sized to be received within base24and with an end51abutting the end plate36of base24. An outer wall52is threaded to mate with the internal threading44of base24. An inner wall53of cylindrical portion50remains spaced from inner cylinder40to define a void for receiving springs as will be described (and as shown inFIGS. 1–2). The collar26also includes a reduced diameter portion54with the reduced diameter portion54and the enlarged diameter portion50connected at an annular stop surface56shown inFIG. 15. For purposes that will become apparent, the reduced diameter portion54includes a slot58at an end59of portion54. Linearly aligned with slot58is a hole61.

The shell28is separately shown inFIGS. 12 and 13. The shell28includes a cylindrical body60sized to be slideably received in close tolerance within the reduced diameter cylindrical portion54of collar26. The cylindrical body60terminates at a flange62positioned to abut stop surface56of collar26. Accordingly, the shell28is slideable within the collar26with the flange62movable between the stop surface56of collar26and the end plate36of base24.

The cylindrical body60has at its end opposite flange62a reduced diameter portion64which is coaxial with the main cylindrical body60. The reduced diameter portion64terminates at a first pressure ring66with the plane of the opening of the pressure ring66being generally perpendicular to the cylindrical axis of body60. An elongated slot68extending generally in the direction of the axis of body60is provided extending through the shell28with the slot68extending substantially the length of the body60and substantially the length but not entirely through the sidewall of the reduced diameter portion64such that ring66is an uninterrupted ring. However, a segmented ring or other incomplete ring would be satisfactory.

The optics housing30is separately shown inFIGS. 7–11and includes a generally cylindrical main body70(with flat side walls71a,71b) having extending axially therefrom a reduced diameter cylinder72(surrounded by surface71) having an annular slot73. The reduced diameter cylinder72is sized to be slideably received within the inner cylinder40of base24as best shown inFIGS. 1 and 2.

The main body70includes a first axial slot74extending partially through a distal end75of the body70. Disposed axially spaced from slot74is a second slot76extending through the main body70. A pin receiving hole77extends through body70perpendicular to slot76. Ninety degrees offset from slots74,76are access holes78in communication with a hollow interior80of cylinder72. Ninety degrees offset from slot74are pockets82,83with axes of the pockets82,83in coaxial alignment with one another and in communication with the slot74. The base end75has a ramped ridge79extending parallel to hole77.

In the assembly, as best shown inFIGS. 1 and 2, a first biasing spring84is positioned to act between the base plate36of base24and the flange62of shell28urging the shell28away from the base plate36. A second biasing spring86is positioned to act against the base plate36of base24and an engaging surface71on cylinder70thereby urging the optics housing30axially away from the base plate36.

As shown inFIGS. 3–6, a light source90is contained within pocket82. A light detector92is contained within pocket83. Electrical leads (not shown) from both the light source90and light detector92may be passed between the opposing exterior surfaces71a,71bof cylinder70and the interior surface of shell cylinder60with the leads then passed through the holes78, into hollow interior80of cylinder72and directed thus into the circuitry (not shown) contained within the housing22. The light source90and light detector92are aligned to define a light path therebetween. The light source90generates a testing wavelength. The light detector92is selected to measure the intensity of wavelengths including the intensity of the testing wavelength.

A lock pin94(shown separately inFIGS. 26–27) is contained within optics housing30in hole77with the lock pin94positioned at a 90° angle to the plane of the slot74. The pin94has a ramp95disposed in slot76. In the assembly shown inFIGS. 1–6, the slots74,76of the optics housing30are in alignment with the slot68of the shell28.

As shown inFIGS. 18–25, the sampler32includes a body100formed of injection molded plastic. The body100includes a rear handle portion101and a forward sampling portion102. The handle portion101is sized to be gripped by the fingers of a user. At the sampling end102, the body100is provided with a hub or piston104. The piston104is cylindrical and sized to be received in close sliding tolerance within the reduced diameter cylinder64of shell28. The piston terminates at a flat second pressure surface106which is generally perpendicular to the axis of the needle10. While a flat surface106is preferred, other shapes (e.g., concave) could be used.

The needle10protrudes beyond the surface106a distance equal to a desired penetration of the needle10into a patient's skin layer. As disclosed in the aforementioned international publication, distance of protrusion of needle10is about 1.5 mm to ensure protrusion of the needle10into but not through a dermal layer of a patient's skin. At the sampling end102, the main body100is provided with a relief108surrounding a hole110formed through the body. The hole110is in communication with a proximal end11of the needle10. Accordingly, an absorbent material12such as the material210′ shown inFIGS. 16–20of the aforementioned International Publication No. WO95/10223 may be placed within the relief108such that interstitial fluid which flows up the needle10will be deposited upon the material12. The material12is held in place through any suitable means such as by an adhesive ring111(or, alternatively, ultrasonic bonding or other bonding technique).

The hole110is positioned at a sampling location such that the hole110is in the light path between the light source90and the light detector92when the sampler32is placed within the apparatus20as will be described. The end102is sized to be received within the aligned slots68,74of shell28and optics housing30, respectively.

The main body100is provided with an arcuate rib113sized and shaped to abut an exterior surface of is the optics housing30on both sides of the slot74and to curve beneath the base75. A latching member112is connected to the body100. The latching member112pivots at a point of connection to the body100and includes a lever arm114exposed at the handle portion101such that the lever member114may be depressed manually by a user. The latch112further includes a latching end116sized and positioned to be received within the hole76of the optics housing30. The latching end116includes a detent118(FIGS. 1–2) positioned to engage and receive the ramp95of the lock pin94within the detent118when the sampler32is inserted within the slots74,76in a predetermined alignment and with the sampling location110disposed within the light path between the source90and detector92. A leading end of the locking end116is provided with a ramped surface to ride over the pin94upon insertion of the sampler32within the optics housing30and to provide a positive lock as the pin is received within the detent118. To further secure the sampler32in optics housing30in the desired alignment, sampler housing100has a detent117(FIG. 23) to receive ridge79on the base75of optics housing30. The sampler32may be easily removed by a user depressing end114thereby raising end116for the pin94to clear the detent118permitting removal of the sampler32from the apparatus.

With the construction thus described, a sampling end102may be placed within the aligned slots74,68. over-insertion is avoided by reason of the sampling end102butting up against the interior of the optics housing30. Further, the lock pin94received within the detent118and the ridge79in detent117ensure that the sampler32is not under-inserted into the slots74,76by providing a user with a positive feedback indicating that the lock pin94has been received within the detent118indicating the sampler32is in the predetermined alignment. Accordingly, upon receipt of such feedback, the user is assured that the sampling location110is in alignment with the light path between the light source90and the light detector92.

The first spring84urges the shell away from the base24such that the full length of the piston104and needle10may clear the first pressure ring66and be inserted through the slot68as the sampler32is loaded into apparatus20.

Due to the locking at detents118and117, sampler32is held in a predetermined alignment with the membrane12in the light path between light source90and light detector92. To facilitate placement of sampler32within apparatus20, the sampler32and apparatus20have mating external geometries. Namely, in the rest position ofFIG. 1, the shell28is fully extended from base36by spring86. Slot58of collar26, slot68of shell28and slot74of optics housing30are aligned to permit insertion of end102of sampler32. Further, in this position, slot68is sized so that needle10may pass ring66without interference. Also, in this position, slot61of collar26, slot68of shell28and hole76of optics housing30are aligned to receive end116of lever arm112.

Upon insertion, the mating geometry of sampler32and optics housing30insure the membrane12is accurately positioned. The ribs113acting against the external surface of optics housing30together with ribs95,79received within detents118,117securely couple the sampler32to optics housing30in accurate alignment and with the sampler32movable with the optics housing30. As the optics housing30moves relative to shell28and collar26, the sizing of slots58,61and68avoid interference with movement of the sampler32.

Upon initial placement of the apparatus against a patient's skin200(FIG. 28), the ring66first contacts a patient's skin200with the needle10being recessed behind the ring66. Upon urging of the apparatus20against the skin200, the ring66moves relative to the needle10against the bias of the first spring84. Upon achieving such relative movement, the needle10then penetrates the skin200with the second pressure surface106of the piston104engaging the skin and with both springs84,86resisting further penetration until both springs are compressed. Second spring86ensures a constant force acts on piston106.

FIGS. 28–30show a sequence of operation of the present apparatus. As shown inFIG. 28, during the rest state, the needle10is recessed behind the first pressure ring66to prevent damage to the needle10and inadvertent skin penetration. Upon initial urging of the pressure ring66against the skin (FIG. 29), the pressure ring66depresses the skin200and makes the skin taut in the area defined by the ring66. Further, the pressurization creates a pressurized area in the zone of the skin layer200directly beneath the ring66. This is desirable since interstitial fluid beneath the skin200is believed to exist at a negative pressure. Creating a pressurized zone beneath the ring66is believed to assist in rapid collection of interstitial fluid within the needle10. During this initial pressurization of the skin200, the ring66moves relative to piston104until the needle10penetrates the skin200and the end106of the piston104abuts the skin200(FIG. 30). Further depression (which can occur against soft skin but which may not occur against more rigid skin) is shown inFIG. 31where the piston end surface106protrudes slightly beyond the ring66to further increase the pressure acting in the collection zone of the skin200and with full penetration of the needle10.

It has been found that this sequence of action significantly increases the rate at which interstitial fluid is collected through the needle10and deposited on the membrane12within the sampler32.

After full penetration of the needle10, internal circuitry may then be actuated to operate the light source92. Absorption of the testing light through the collected sample provides an indication of the amount of the constituent contained on the sample.

In a preferred embodiment, springs84,86are preloaded. Namely, in the rest position ofFIGS. 1 and 28, first spring84exerts an urging force on shell28of about three pounds and with a spring constant of about four pounds per inch. Spring86is pre-loaded to about one pound and has a spring constant of about two pounds per inch. To accommodate the pre-loading of springs84,86, optics housing30is provided with a retaining ring202(shown only inFIGS. 1 and 2) in slot73. The pre-loading of spring84insures a minimum skin pressure by ring66before penetration of the skin200by needle10.

As shown best inFIGS. 1,2and18, membrane12is provided with a U-shaped boundary300. Boundary300is formed by ultrasonically or pressure treating membrane12to create a material density in boundary300which is greater than a material density of the remainder of the membrane12. Therefore, boundary300provides an increased resistance to liquid flow compared to the remainder of the absorbent membrane12. The end11of needle10is positioned to deposit interstitial fluid onto the interior of the U-shaped boundary300. The increased density of the boundary300permits the fluid to flow within the interior of the boundary300but restricts fluid flow beyond the boundary300. The target location (“T”) of light through membrane12during testing is positioned within the boundary300. Boundary300thus insures that a sufficient volume of collected fluid is in residence at the target location T during testing.

It will be appreciated that through use of the present invention the rate at which interstitial fluid is collected through the needle10is greatly enhanced over that shown in the aforementioned International Publication No. WO95/10223. Further, the sampling apparatus is contained within the low-cost sampler32which can be readily disposed of after each use. The mating geometry of the sampler32with the internal geometry of the apparatus20ensures that the sampler32is placed within the apparatus20in a predetermined alignment with the sampling location in the light path between the source90and the detector92. The sampling apparatus also ensures a proper positive locking position which may be released easily by an operator and the entire operation of insertion of the sampler within the apparatus and removal of the sampler for subsequent disposal is easily accomplished for a patient.

B. Second Described Embodiment

FIGS. 32 through 39illustrate an alternative embodiment of the present invention. In these figures, the base24of the previous described embodiment as well as collar26, shell28and optics housing30are replaced with a piston housing400which slideably receives two hollow pistons402. The pistons402are disposed to move in generally parallel paths of travel relative to the piston housing400.

The piston housing400is retained in a stationary position (relative to tool handle22ofFIG. 1) by means of clam shell back404which is adjoined to claim shell front406. The clam shells404,406may be connected to the apparatus housing22as in the previous described embodiment. The clam shell front406has an axially extending slot408. Bottom ends of the hollow pistons402are secured to a pressure ring shell412by means of screws or bolts414(FIG. 34). An optical core420is provided with the pistons402passing through aligned holes422of the core such that the core420is movable relative to the piston housing400and the pistons402. A flange403on clam shells404,406limits downward movement (in the view ofFIG. 34) of optical core420.

Best shown inFIG. 34, outer springs416surrounds the pistons402between the piston housing400and the optical core420such that springs416compress when the movable optical core420moves upwardly (in the view ofFIG. 34) relative to the stationary piston housing400. Further, springs418are positioned within each of the hollow pistons and opposing the housing22(not shown inFIG. 34but shown inFIG. 1) such that the springs418are compressed as the pressure ring shell412and the pistons402move upwardly (in the view ofFIG. 34). The optical core420included a block member421as a separate element to permit ease of machining of optical core420. The optical core420has an axially extending slot424(defined by walls427) on a forward side thereof (aligned with slot408on front clam shell406) and sized to receive the sampler410as will be described. Further, the pressure ring shell412has an axial slot413(aligned with slot408). The walls427are received within slots408and413.

An optics housing430is secured to the optical core420for movement therewith. The optics housing430carries an optical source432as well as optical detectors434and a beam splitter436(shown only inFIG. 34). The optical source432directs infrared light to the beam splitter436which splits the beams into signals, each directed to detectors434, to enhance optical analyzing of the signal. The source432directs the infrared light through an optical path which passes through a slot431formed in the optics housing430. Slot431is aligned with slots424and408. A ball plunger438is urged by a spring440into slot436. A cam pin442is carried in the deployment block421in order to protrude into the slot424. Finally, a fan is preferably provided for drying any sample within the apparatus. While the fan impeller is not shown, the fan shroud444is shown into which a fan impeller may be placed for blowing air through the optical core420and the optics housing430.

An enhanced design sampler410includes a handle end409and a sample end411. The handle end409is a hollow sampler housing. The interior500of end409is sized to completely receive the sample end411. The housing409is sized to be received within the slot424.

As best shown inFIG. 36, side walls of the housing409have bottom edges501which are positioned against and ride on inwardly protruding rails425of the optical core420at the bottom of slot424. The sample end411is pivotly secured to the sampler housing409at a pivot pin502. As a result, the sample end411can pivot between a storage position shown inFIG. 36with the sampler end411fully received within the interior500of handle409in order to protect the sample end411and its constituent components from destructive impact or contamination.

The sample end411can pivot from the storage position ofFIG. 36to a sample position shown inFIG. 39. The sample end411contains the membrane504for receiving a sample of interstitial fluid. Further, the sample end411contains a hub506terminating at a pressure ring508. The hub506contains a needle510for collecting interstitial fluid and depositing the interstitial fluid on the membrane501as previously described.

In the storage position ofFIG. 36, the membrane504is contained with the housing409to prevent damage as well as contamination (such as from finger prints or other skin oil). Further, in the storage position, the needle510is protected from damage as well as protecting a user from undesired contact with the needle510.

In the sample position ofFIG. 39with the sampler410fully inserted, the membrane504is positioned in the optical pathway, T, between the light source and the light detectors. Further, the needle510is positioned centrally aligned with the pressure ring415. The hub506and ring508are sized to freely pass through the ring415. Also, in the position ofFIG. 39, the ball plunger438(shown only inFIG. 33) moves along an axis Y—Y to be received within in a detent512formed within the sample end411in order to retain the sample end411in position.

When in the sample position, flanges514on the sample end411oppose and abut against a stop surface516on the optics housing430, (FIG. 34). As a result, the opposition of the flanges514and surface516prevents upward movement of the sampler relative to the optics housing430. Simultaneously, opposition of the bottom edges501to the rails425prevents downward movement of the sampler410relative to the optics housing430. The reception of the ball plunger438within the detent512restricts left and right movement (within the view ofFIG. 39) of the sampler410relative to the apparatus. Further, such reception of the ball plunger438within the detent512provides a tactile sensation to the user indicating that the sampler410has been fully seated with the apparatus. With the sampler410fully received with the apparatus, the membrane504is positioned within the light path, T, and the needle510is axially aligned with the hub.

The sample end411is pivoted to the sample position ofFIG. 39as the housing409is urged within the slot424. Specifically, the cam442abuts a first cam follower520on the sample end411.FIGS. 36 through 39illustrate the sequence of operation for pivoting the end411to the sample position. InFIG. 36, the sample end411is in the storage position and the handle409is in the process of initial insertion into the slot424with the bottom edges501of housing409riding on rails425. The cam pin442is opposing the first cam follower520. Upon further insertion of the housing such that the leading end503of the sample end411moves toward abutment with a wall505of the optical core420(FIG. 36), the cam pin442pushes against the cam follower520causing pivoting movement of the sample end411about the pivot pin502as illustrated inFIG. 37.FIG. 38illustrates full pivotal movement of end411with end411not yet fully advanced to a full seated position.FIG. 39illustrates full insertion of sampler410with the detent512aligned with the axis Y—Y of the pin438and with the membrane504aligned with the optical pathway, T. The compression of cam pin442against surface520prevents downward pivoting of end411and edge514against stop surface516(FIG. 34) prevents upward pivoting thereby locking end411in place with pin438in detent512and with the target area of membrane504in the light path. At this point, the apparatus can be used by urging the ring end415against the skin (preferably in the arm region). In response to such urging, the pressure ring shell412and attached hollow pistons402move upwardly to compress the springs418. Following initial upward movement of the ring415relative to the hub506, the needle penetrates the skin and the hub end508further engages and pushes against the skin with causation of movement of the optical core420and attached optics housing430and sampler410against the urging of the springs416. The thus described dual operation of two pressure rings415,508operating against the urging of two springs416,418is more fully described with reference toFIGS. 28trough31.

After a fluid sample has been collected and/or tested, the patient can remove the tool from the arm such that the components return to the relative positioning shown inFIG. 34. At this point, the user can grasp the handle409to pull the sampler410out of the apparatus. This pulling causes the detent512to become disengaged from the ball plunger438and further causes the cam pin442to engage a second cam follower522as illustrated inFIG. 40. The engagement of the cam pin442with the second cam follower522urges the sampler end411to pivot from the sample position toward the storage position. An internal wall580acts as a stop to limit movement of end411and hold it in the full storage position.

The interior500of the housing contains a retention spring524on the housing409. The retention spring524acts against an arcuate surface526on the sample end411. The surface526terminates at a detent528to receive the retention spring524. Therefore, when the sample end411is in the storage position ofFIG. 36, the retention spring524is received within the detent528preventing movement of the sample end411out of the storage position until an adequate force acts on the cam follower520to cause pivoting movement around pivot pin502.

When the sample end411is in the sample position ofFIG. 38, the spring524has no deflection and is at rest. However, as the sample end411is moved from the sample position toward to the storage position, the arcuate surface526engages the spring524, causing the spring524to deflect and create a spring force. When the pin442acts against the second cam surface522(FIG. 40) to partially move the sample end411to the storage position, the deflected spring524is received within the detent528to thereby urge the sample end411to the full storage position and retain the sample end411in the full storage position.

Having described this second improved embodiment, it will be noted that the needle510and the membrane504are fully protected when the sampler410is not inserted into the apparatus. The membrane504and the needle510are only deployed after the housing409is initially inserted into the apparatus (i.e., into slot424) with the cam pin442engaging the first cam follower520.

C. Additional Enhanced Embodiments

In the embodiment ofFIG. 1and as disclosed in the aforementioned patent application Ser. No. 08/321,305 and 08/136,304 corresponding to PCT International Publication No. WO95-10223, the sampling needle such as needle10terminates at a free end11which has the plane of its opening perpendicular to the plane of the membrane12. Stated another way, the longitudinal axis of the needle10is parallel to and spaced from the surface of the membrane12.

The present embodiment ofFIGS. 33–40use an enhanced positioning of the needle510relative to the membrane504. With attention toFIGS. 42 and 43, the sample end411includes a recess600sized to receive the needle510. Further, the sample end includes a raised circular ring602surrounding the opening604through which the IR light is to pass. Between the ring602and the body of the sample end411an annular recess606is provided. The free end601of the needle510passes through the recess600and nearly abuts the ring602. Accordingly, the membrane504can be placed on the ring602and depressed into the recess606. The membrane504can then be secured within the recess606through any suitable means such as ultrasonic welding or the like. With this embodiment, the open end601is now disposed parallel to opposing material of the membrane504in a transfer area, A, of the membrane rather than perpendicular to it. Stated another way, the longitudinal axis of the needle is perpendicular to opposing membrane material in the transfer area, A, with open end601directly abutting (or at least in close proximity to) the membrane material. As a result, fluid flowing from the needle510need not make a 90° bend to be deposited on membrane504. Instead, the fluid can flow directly onto the membrane504and be wicked on to the membrane material to a test area, T, covering opening604. This enhances the transfer of fluid from the needle510to the membrane504. Further, with this arrangement, the material of the membrane504can act as a filter to filter out undesirable blood cells or cell fragments which may, from time to time, be transferred through the needle510to the membrane504. The transfer of blood cells or cell fragments onto the membrane504can also be reduced by providing a protein filter on the membrane in the region610(a filter area). Such a protein filter can be a physical filter or a filter composed of a binding agent (for example a chemical in that region to which blood, cell fragments, or other proteins may naturally attach to prevent further transfer of the proteins into the target, T, area of the membrane). Examples of such binding agents are diethanolamine, carboxymethylcellulose, quaternary amines, and anti-RBC antibodies.

Having disclosed the present invention and a preferred embodiment, it will be appreciated that modifications and equivalents of the disclosed concepts may readily occur to one skilled in the art. It is intended that such modifications and equivalents shall be included within the scope of the claims which are appended hereto.