Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This non-provisional application is related to and claims priority based on U.S. Provisional Application No. 60/424,414, entitled “Automatic Biological Analyte Testing Meter with Integrated Lancing Device and Methods of Use,” filed on Nov. 6, 2002, which is incorporated herein in its entirety by this reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    In general, this invention relates to skin lancing devices, analyte sensors and analysis meters for determining biological analyte levels, and more specifically, a portable device that integrates the functions of these separate devices in a single unit. 
       BACKGROUND OF THE INVENTION 
       [0003]    Methods and devices used by a patient to measure a bioanalyte are well known in the art. For example, currently available technology allows a diabetic patient to monitor his own blood glucose level by drawing a blood sample with a lancing device, using an electrochemical sensor strip to capture the blood sample, and using an electronic meter connected to the sensor strip to analyze the blood sample and display the result. Until recently, relatively large sample volumes were required to be drawn, generally 3 microliters or more of blood or other biological fluid. These fluid samples are obtained from a patient, for example, using a needle and syringe, or by lancing a portion of the skin such as the fingertip and “milking” the area to obtain a useful sample volume. These procedures are inconvenient for the patient, and often painful, particularly when frequent samples are required. Less painful methods for obtaining a sample are known such as lancing the arm or thigh, which have lower nerve ending density. However, lancing the body in these preferred regions typically produces submicroliter samples of blood, because these regions are not heavily supplied with near-surface capillary vessels. The recently introduced FreeStyle™ Blood Glucose Monitoring System developed by TheraSense, Inc. of Alameda, Calif., is capable of consistently, accurately and precisely measuring sample sizes of only ⅓ microliter using this preferred “alternate site testing” (AST). U.S. Patent No. 6,299,757, issued Oct. 9, 2001 to TheraSense, Inc. and incorporated herein by reference describes the construction and operation of the above FreeStyle system. U.S. Pat. No. 6,283,982 issued Sep. 4, 2001 to TheraSense, Inc. and incorporated herein by reference describes a lancing device that is used in the FreeStyle system. 
         [0004]    A ⅓ microliter sample is about the size of a pinhead. Elderly patients and those with reduced eyesight and dexterity can have problems seeing and capturing such a small sample. Current testing procedures involving a lancing device, disposable lancets, meter and disposable test strips involve a lot of steps. It can be difficult for patients to remember all the steps and their proper order. Active patients testing outdoors, for example, can have a tough time juggling all of the different pieces during a test. Also, younger patients want to be able to quickly and discreetly test themselves without drawing attention with a lot of paraphernalia and testing steps. 
         [0005]    What is needed and has not been provided by the prior art is a simpler testing method using a compact, unitary testing device. 
       SUMMARY OF THE INVENTION 
       [0006]    The testing instrument of the present invention provides a method for obtaining a sample and testing that sample using a single device. Further, the instrument automatically performs all the testing steps in the proper order with the proper delays for each. The entire testing process is initiated by the patient with a single press of a button. The instrument automatically inserts and retracts a lancet into the skin with the proper speed and force, waits a predetermined time for a fluid sample to form on the skin, aligns the fill channel of a test strip with the small fluid sample and brings the two into contact to capture the sample, indicates to the patient when a sufficient sample has been captured, waits for electrochemical testing of the sample to be complete, displays the test result to the patient, and records all of the test results for later review, analysis and/or uploading to a computer network. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a top perspective view showing a unitary lancing device, test strip applicator and testing meter constructed according to the present invention. 
           [0008]      FIG. 2  is a side elevation view showing the unitary handheld instrument of  FIG. 1 . 
           [0009]      FIG. 3  is a bottom perspective view schematically showing the cap, test strip and lancet on the instrument of  FIG. 1 . 
           [0010]      FIG. 4  is a front cross-sectional view schematically showing lancet positioning features. 
           [0011]      FIG. 5  is broken away perspective view schematically showing a concentric spring lancing mechanism. 
           [0012]      FIG. 6  is a perspective view schematically showing a torsion spring lancing mechanism. 
           [0013]      FIG. 7A  is a perspective view of a first embodiment of an inventive lancet and cap combination. 
           [0014]      FIG. 7B  is a perspective view of a second embodiment of an inventive lancet and cap combination. 
           [0015]      FIG. 7C  is a perspective view of a third embodiment of an inventive lancet and cap combination. 
           [0016]      FIG. 7D  is a perspective view of a multi-pointed lancet. 
           [0017]      FIG. 7E  is a schematic view showing possible locations of test strip fill channels in relation to fluid samples created by the lancet of  FIG. 7D . 
           [0018]      FIG. 7F  is a perspective view of a right-angle lancet. 
           [0019]      FIG. 8  is a side elevation view schematically showing a lancet retention and ejection mechanism. 
           [0020]      FIG. 9A  is a front elevation view schematically showing a vertical test trip trajectory. 
           [0021]      FIG. 9B  is a front elevation view schematically showing an arcuate test trip trajectory. 
           [0022]      FIG. 9C  is a graph showing blood sample location versus fill success rate for vertical trajectory test strips. 
           [0023]      FIG. 9D  is a graph showing blood sample location versus fill success rate for arcuate trajectory test strips. 
           [0024]      FIG. 10  is a front cross-sectional view schematically showing test strip guiding features. 
           [0025]      FIG. 11  is a bottom perspective view schematically showing the strip motion and cap removal interlock on the instrument of  FIG. 1 . 
           [0026]      FIG. 12  is a perspective view of a test strip moving mechanism. 
           [0027]      FIG. 13  is a side elevation view of the test strip mechanism of  FIG. 12 . 
           [0028]      FIG. 14  is schematic view showing a test strip fill channel location coding and translation scheme. 
           [0029]      FIG. 15  is fragmentary side elevation view showing the use of a Shape Memory Alloy to activate a test strip mechanism similar to that of  FIG. 12 . 
           [0030]      FIG. 16A  is a perspective view showing an alternative embodiment of a test strip moving mechanism in the loading position. 
           [0031]      FIG. 16B  is a perspective view showing an alternative embodiment of a test strip moving mechanism in the testing position. 
           [0032]      FIG. 17A  is a perspective view showing another alternative embodiment of a test strip moving mechanism in the loading position. 
           [0033]      FIG. 17B  is a perspective view showing another alternative embodiment of a test strip moving mechanism in the testing position. 
           [0034]      FIG. 18  is a perspective view showing yet another alternative embodiment of a test strip moving mechanism. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]    Referring to  FIG. 1 , an integrated device  10  is shown that functions as an automatic lancing device, test strip applicator and testing meter. Integrated device  10  includes function buttons  12  and  14 , liquid crystal display  16 , display backlight button  18 , actuator button  20 , cocking collar  22  and lancing depth control thumbwheel  24 . Preferably device  10  has a plastic housing  26  having upper shell  28  and lower shell  30 , forming a main body portion  32  and head portion  34 . 
         [0036]    Referring to  FIG. 2 , integrated device  10  has a lancet ejection lever  36 , a clear protective cap  38 , and a strip return and cap removal lever  40 . Disposable electrochemical test strip  42  with side fill channels  44  is shown in the loading position. The construction and manual use of a side-file test strip  42  is fully described in U.S. Pat. No. 6,338,790 issued on Jan. 15, 2002 to TheraSense, Inc., and U.S. application Ser. No. 09/434,026, filed Nov. 9, 1999, both incorporated herein by reference. Preferably, an existing test strip, such as the FreeStyle™ brand test strip developed and marketed by TheraSense, Inc., is used with the present invention rather than a propriety format designed especially for the integrated device. Advantages to using existing test strips include utilizing existing research and development, manufacturing, distribution, and inventory systems and having larger economies of scale, thereby allowing for a lower cost test strip. Also, a large user base of patients are already familiar with the existing strips, and if they desire, can alternately use the same strips in existing manual meters and in the automatic device. 
         [0037]    Referring to  FIG. 3 , features of clear protective cap  38  are shown. Also shown is a vertically oriented, disposable lancet  46  having a plastic main body  48 , a sharp  50  and removable cap  51  for covering sharp  50  when not in installed in device  10 . Device cap  38  has a recess  52 , preferably for resting on a patient&#39;s arm or leg. In use, the device  10  is held as shown in  FIG. 2 , and preferably oriented generally above and perpendicular to the arm or leg. Aperture  54  is provided in the bottom of cap  38  for allowing at least the sharp  50  of lancet to pass through to the patient&#39;s skin during actuation. Slotted opening  56  is provided in one side of cap  38  to allow test strip  42  to pass from the outside loading position to the inside sample gathering position. Other than these two openings, cap  38  completely surrounds lancet  46  before, during and after testing. 
         [0038]    To achieve good lancing results, a pressure applicator ring  57  should be provided around aperture  54 . Ring  57  helps provide the proper skin tension and capillary blood pressure to ensure that lancet  46  pierces the skin with minimal pain and a sufficient amount of blood is expressed from the wound. In the preferred embodiment, ring  57  is semi-toroidal in shape, has a major diameter of about 11 millimeters, stands about 2 millimeters off of cap  38 , and has a width or minor diameter of about 1 millimeter. It is also advantageous to provide a land 1 to 2 millimeters in width between aperture  54  and ring  57 . For best results, ring  57  and the enclosed land should be continuous, but they can also be segmented as shown. For further disclosure of pressure applicator ring design, see U.S. Pat. No. 6,283,982 issued Sep. 4, 2001 to TheraSense, Inc. and entitled “Lancing Device and Method of Sample Collection,” incorporated herein by reference. 
       Lancet Guiding and Puncture Site Location Control 
       [0039]    Referring to  FIG. 4 , the lancing operation of integrated device  10  will be described. Since integrated device  10  is to automatically bring the fill channel opening  44  of a test strip  42  (shown in  FIG. 2 ) into contact with a small blood droplet brought up from a lancet puncture in human skin, the device should have very good control over the location of that puncture. Otherwise the mechanism would have little chance of successfully bringing fill channel  44  to the droplet. Control over the puncture site location is achieved, in part, by controlling the tolerances of mechanical features on lancet  46  and then guiding lancet  46  closely over the few millimeters of its travel immediately before it punctures the skin. 
         [0040]    On the plastic lancet body  48  itself, the overall dimensions of some guiding feature, located as close to the puncturing tip as possible, should be held to very close tolerances. Features in device  10  mate closely to this guiding feature, but allow it to slide in the direction of lancet travel, giving tight control over the location of the lancet body  48 . The location of the lancet sharp  50  within the plastic lancet body  48  is then carefully controlled with respect to the guiding feature, and finally the point of sharp  50  is located precisely with respect to the outside of sharp  50 . 
         [0041]    In the embodiment of integrated device  10  shown in  FIG. 4 , the guiding feature on the lancet  46  is a cylindrical collar  58  about 3 mm from the needle point, concentric with needle  50 . The outside diameter of collar  58  is controlled to ±0.05 mm and needle  50  is concentric to the outside diameter of collar  58  within ±0.05 mm. The needle point is created by grinding 3 radially symmetric faces, each canted 10° from the needle circumference toward the axis of needle  50 . These faces meet at a common point located on the axis of needle  50  and defining the center of the needle&#39;s diameter. 
         [0042]    The lancet guiding collar  58  slides inside a cylindrical bore  60  in device  10  preferably with a diametral clearance of no more than 0.13 mm. The lancet collar  58  and bore  60  engage at this close fit only for the final 5 mm of the lancet&#39;s travel (starting when the needle point is about 2 mm above the skin surface), as earlier engagement would reduce the kinetic energy of lancet  46  through friction and air pressure. 
         [0043]    Referring to  FIG. 7C , an alternative lancet  62  having a blade-shaped sharp  64  and plastic body  66  can be used instead of the needle-shaped lancet  46  described above. Testing has shown that bladed lancet  62  may draw more blood than needle lancet  46 . More importantly, because of constraints in the insert molding processes in which the metal sharps  50  and  64  are molded within plastic housings  48  and  66 , respectively, tighter tolerances between the sharp and outside surface of the lancet housing can be obtained by using bladed lancet  62 . This aids in more precisely maintaining the location of the blood drop formed on the skin after lancing, thereby allowing more precise alignment between test strip  42  and the blood droplet for more reliable filling of fill channel  44 . 
       Concentric Spring Lancing Mechanism 
       [0044]    Referring to  FIG. 5 , a first lancet driving and retraction mechanism is shown. Feedback from marketing focus groups shows that customers desire an integrated device having a low profile head. In order to make the head  34  of integrated device  10  as short as possible, the lancet drive mechanism needs to have a short height. A typical drive system is comprised of a drive spring and a retraction spring, often placed in series (a line) or parallel (lying next to each other). In the first mechanism embodiment shown in  FIG. 5 , lancet  46  is received within lancet holder  68  which is captivated within drive spring  70 , which in turn is nested within retraction spring  72 . This concentric arrangement minimizes the vertical space the components occupy, and minimizes any eccentric forces that might disturb the predictable linear motion of lancet  46  on firing. 
       Torsion Spring Lancing Mechanism 
       [0045]    Referring to  FIG. 6 , a second lancet driving mechanism is shown. A typical wound-wire coil spring, such as springs  70  and  72  described above, applies a non-uniform force that depends on the amount it is deflected. It also can compress only to a minimum height determined by the wire diameter and number of coils (solid height). One way to obtain more uniform spring force and avoid the limitations of a spring&#39;s solid height is to use a torsion spring  74  to drive lancet holder  68 ′. Torsion spring  74  can be adjusted for force and travel without significantly affecting the overall mechanism size because the body of the spring does not lie in-line with the rest of the mechanism. 
       Large Lancet Cap for Handling 
       [0046]    Referring to  FIGS. 7A ,  7 B and  7 C, alternate embodiments of lancets and caps are shown. Another factor that affects the overall size of the lancing mechanism is the length of the lancet itself. Traditional disposable lancets, such as shown in  FIG. 3 , have an elongate body  48  and a short cap  51 . In order to reduce the profile of device head  34 , a shortened lancet  76  can be used that is just long enough to engage lancet holder  68  (shown in  FIG. 6 .) This short length might make the lancet difficult for the user to handle and install, so the protective cap  78  (that is removed before use) should be made much larger than usual to aid handling. Cap  78  may be an integrally molded, pull-off tab such as shown in  FIG. 7A , or may be a hollow cap  80  with large handle molded separately or in the same cavity as lancet  76  and placed over lancet  76  after molding, such as shown in  FIG. 7B . A hollow cup or solid “pin cushion” type area  82  can be provided at the opposite end of cap  78 , as shown in  FIG. 7A , to cover the sharp during removal from the device and disposal. 
         [0047]    Referring to  FIG. 7C , a lancet  62  having a blade-shaped sharp  64 , short body  66  and large cap  84  is shown. Traditional and previously described lancets with needle-shaped sharps have their caps removed by twisting. Twisting off the cap of a bladed lancet would likely damage or move the skin piercing edge, resulting in a painful and/or ineffective lance, or inaccurately placed droplet of blood. To assist patients who may be used to twisting caps off of lancets, non-twist features have been incorporated into lancet  62 . First, enlarged cap  84  is formed in the shape of an arrow, reminding patients to pull cap  84  off of lancet  62  rather than twisting. Second, non-circular mating collars  86  and  88  are provided on lancet body  66  and cap  84 , respectively. When cap  84  is mated with body  66 , these collars  86  and  88  are keyed or aligned with each other. Twisting would cause these non-circular collars  86  and  88  to be misaligned, suggesting that this action should not be undertaken. Third, a widened portion  90  is provided on sharp blade  64  away from the narrow distal end, providing resistance to twisting, or making damage to sharp  64  from twisting unlikely. Widened portion  90  provides other benefits as well, such as acting as a redundant maximum sharp penetration depth control in the event of failure of other depth control measures. Widened portion  90  also aids in fabrication of lancet  62 , as this configuration is less susceptible to chattering during grinding. 
         [0048]    Lancet cap  84  is also provided with pin-cushion type areas  82 ′ and  82 ″, either of which can be used for receiving sharp  64  after use and prior to disposal. Area  82 ″ offers the advantage of allowing the user to extend cap  84  up into device cap  38  to cover sharp  64  while lancet  62  is still in place in integrated device  10 . In this manner, used lancet  62  and cap  84  can be ejected from device  10  together as a unit so that the user need not handle small lancet  62  separately while trying to align it with cap  84 . 
       Bladed Lancet Oriented Parallel to Strip 
       [0049]    If the width of the cutting edge of sharp  64  is such that it creates an oblong rather than circular blood droplet footprint, the cutting edge should be aligned parallel to test strip  42  (i.e. parallel to the axis of device  10 ) rather than perpendicular to it, since this is the critical alignment axis, as will be described later. The flat shape of lancet body  66  allows for such alignment and prevents misalignment. 
       Multi-Pointed Sharp 
       [0050]    Referring to  FIG. 7D  a lancet  116  having a multi-pointed sharp is disclosed. In this embodiment the lancet has two points  118 , although in other embodiments (not shown) three or more points  118  could be arranged inline or in other patterns. Each point  118  creates its own skin puncture and blood droplet  104 . (Two blood droplets  104 , if they are spaced closely together and/or become large enough, may merge into a single oblong or round blood drop.) If integrated device  10  is arranged so that points  118  are aligned parallel to strip  42 , the blood droplet  104  and fill channel  44  positioning shown in  FIG. 7E  results. As shown, the longitudinal position of fill channel  44  relative to blood droplets  104  can be widely varied while still maintaining enough contact with at least one blood droplet  104  to cause fill channel  44  to wick up sufficient blood. Therefore, the use of a multi-pointed sharp allows the positional tolerances of strip  42  and/or lancing to be relaxed while improving strip fill performance. 
       Right-Angle Lancet 
       [0051]    Referring to  FIG. 7F , a right-angle lancet  89  is disclosed. The main advantage of this configuration is that it has an elongated body similar to that of traditional lancet  46  (shown in  FIG. 3 ) making it easy to hold and manipulate, but this long dimension is oriented perpendicular to the lancing axis, thereby contributing to the previously stated goal of making device  10  low profile in height. The body of lancet  89  should be flat or keyed to allow the lancet holding mechanism to keep sharp  50  oriented properly with the lancing axis. Lancet  89  can be driven downward in a pure vertical translation along a straight lancing axis, or it can be rotated about a horizontal axis such that sharp  50  travels in an arc and becomes perpendicular to the patient&#39;s skin just as it punctures the skin. 
       Lancet Retention and Ejection 
       [0052]    Referring to  FIG. 8 , the mechanism by which a disposable lancet  76  is retained within the plunger portion  91  of the integrated device lancing subsystem is shown. Lancet body  77  is generally flat and has a notch  92  on each edge for receiving barbs  94  on the plunger&#39;s flexible retaining arms  96 . The angles of the lancet&#39;s notches  92  and the arms&#39; barbs  94  are chosen to draw lancet  76  into the plunger. 
         [0053]    To eject lancet  76 , the lancing subsystem mechanism urges lancet  76  out of plunger  91 , forcing retaining arms  96  to flex outward. Once lancet  76  has moved far enough, barbs  94  bear on the tapered tail  98  of lancet  76  and their inward force translates to a longitudinal displacement of lancet  76 —they will cause lancet  76  to eject. 
         [0054]    The mechanism may use a linear plunger to eject the lancet (pushing in the downward direction in  FIG. 8 ), or a wedge that bears between some feature on lancet and the plunger body. For instance, to further reduce the height of plunger mechanism  91 , a wedge-shaped eject lever could extend perpendicularly into the plane of  FIG. 8  and contact rear tapered edge  100  to urge lancet  76  downward and out of device  10 . Preferably, an interlock mechanism is incorporated so that lancet  76  cannot be ejected while cap  38  is still in place. Alternatively, the ejection lever can be located inside cap  38  to achieve this same result. 
         [0000]    Strip Loading Protected from Sharp 
         [0055]    Referring again to  FIG. 3 , loading of test strip  42  will now be discussed. In the compact integrated device  10 , test strip  42  and sharp  50  are located fairly close together. In order to eliminate the likelihood of the user accidentally sticking himself on the lancet sharp  50  while inserting a test strip  42 , integrated device  10  is arranged so that a test strip  42  can be inserted without removing the protective cap  38  from head  34  of the device. 
         [0056]    Cap  38  covers the lancet sharp  50  at all times and is removed only to replace the lancet  46 . Test strip  42  is inserted into a slot  102  in lower housing shell  30  on the outside of cap  38 , and the device mechanism moves strip  42  from this loading position into the interior of cap  38  and to the testing position near lancet sharp  50 . The same mechanism moves test strip  42  away from sharp  50  and returns it to the load position for disposal after a test. 
       Test Strip Trajectory 
       [0057]    Referring to  FIGS. 9A and 9B , strip trajectories will be discussed. One of the biggest challenges in developing an automated, integrated device is creating an autonomous mechanism that can introduce a test strip  42  into a small blood sample and get an acceptably high rate of successful fills (blood entering test strip test chamber). Laboratory experiments indicate that the trajectory along which strip  42  moves into contact with the blood droplet  104  has a significant effect on this success rate. 
         [0058]    Referring to  FIG. 9A , initial experiments held a test strip  42  at a 65° angle to the sample platform  106 , and moved strip  42  along a straight line perpendicular to platform  106 . The edge  108  of strip  42  entered droplet  104  from above and stopped moving once it contacted the sample substrate (a glass slide). This arrangement produced erratic fill rate results, and showed a limited acceptable range of mislocation tolerance between droplet  104  and the strip  42  nominal location, as shown in  FIG. 9C . 
         [0059]    Referring to  FIG. 9B , in subsequent experiments the test fixture was modified so it held test strip  42  at a 35° angle and moved it along a 25 mm radius arc whose axis was parallel to strip  42  and sample platform  106 . The axis location was chosen so that edge  108  of strip  42  was tangent to sample platform  106  at the lowest point of the trajectory. When in use, strip  42  would be moving approximately parallel to and touching the surface of the sample substrate as fill channel  44  on strip edge  108  contacted droplet  104 . This trajectory provides much more consistent results and a higher successful fill rate, as well as a significantly larger tolerance for mislocation, as shown in  FIG. 9D . It is believed that the wider tolerance is due to the “squeegee” action of this trajectory, as it tends to scrape blood off the substrate and push it along in front of strip  42  until strip  42  stops moving. 
         [0060]    Referring to  FIGS. 12 and 13 , a test fixture demonstrating an alternative strip trajectory is disclosed. In this mechanism, one end of test strip  42  is received within electrical connector  120  which is attached to mount block  122 . Mount block  122  is slidably attached to pivot arm  124 , which in turn is pivotably attached to base plate  126  with pivot bolt  128 . Compression spring  130  biases mount block radially outward from pivot bolt  128 . Guide pin  132  is attached to mount block  122  and travels in cam slot  134  formed in base plate  126 , causing spring  130  to compress as mount block  122  and guide pin  132  travel from left to right along cam slot  134 . Torsion spring  136  mounted on pivot bolt  128  drives pivot arm  124  counter-clockwise when release pin  138  is pulled from hole  140  in pivot arm  124 , such as by an electric solenoid, motor, or manual release lever. 
         [0061]    The trajectory of strip  42  in this embodiment is controlled by cam slot  134 . It can be seen that the right end of cam slot  134  has a portion  142  that angles downward just before a short horizontal portion  144  at the right extremity. Angled portion  142  yields a strip trajectory that prevents device cap  38  from having a knife-like edge along the slotted opening where test strip  42  partially emerges from cap  38  to contact the patient&#39;s skin. Short portion  144  allows strip  42  to squeegee along the patient&#39;s skin before it comes to rest. In the preferred embodiment, this travel distance along the skin is about 1 mm. Making this distance longer increases the risk that strip  42  may possibly be impeded by a skin irregularity, such as a raised mole. Making this distance shorter increases the risk that strip  42  lands directly on sample  104  and does not capture the entire sample when moving along the skin. In the preferred embodiment, strip movement mechanism  160  is designed to have test strip edge  108  come to rest in the center of sample  104 , with tolerances such that edge  108  may undershoot the sample center by 0.005 inch and may overshoot it by 0.010 inch. 
         [0062]    In this embodiment, the remainder of cam slot  134  (to the left of angled portion  142 ) is not an arc concentric with pivot bolt  128  because it is desirable to have the test strip loading location farther to the left of the lancing location to allow sufficient room for the user&#39;s fingers to insert the strip. This non-concentric slot  134  is the reason for the slidable, spring loaded arrangement between mount block  122  and pivot arm  124 . 
         [0063]    Other strip angles and trajectories can be alternatively used, keeping in mind that strip fill performance is improved when the strip approaches the target sample from the side. Also, good machine design practice dictates that the maximum pressure angle (the angle between a line drawn from the axis of rotation to the point of contact, and a line orthogonal to the cam surface at the point of contact) be no more than 30°. In other alternative embodiments, the entire strip need not be moved. For instance, the proximal end of strip  42  can be held stationary while the distal end is deflected away from and/or toward droplet  104  with cams, rollers, guides or other suitable devices. Or, as shown in  FIGS. 16A ,  16 B,  17 A,  17 B, or  18 , the strip can be translated in a vertical or inclined line and the squeegee action can be accomplished by a compliant member such as a leaf spring or compression spring. Alternatively, the distal end of strip  42  may follow a helical path as the proximal end is simultaneously lowered and rotated (not shown.) 
       Strip Guiding and Location Control 
       [0064]    To aid in aligning test strip  42  more precisely in its longitudinal direction with the target blood droplet, connector  120  is preferably biased outwardly when in the strip loading position (as shown in  FIG. 12 ) and allowed to be urged inwardly in the direction of arrow A as mount block  122  travels to the blood acquisition position. This can accomplished by wave washers between pivot bolt  128  and pivot arm  124 , or by other compliant measures such as flexure  146  formed in mount block  122 . As mount block  122  moves downwardly, cam surface  148  on its distal end can contact a mating feature on device cap  38  to move test strip longitudinally into a known and repeatable position. In this manner the number of parts requiring closely controlled tolerances on their interfaces for this longitudinal positioning can be limited to strip  42 , connector  120 , mount block  122  and cap  38 , instead of a whole chain including the above parts and others having moving interfaces such as pivot arm  124 , pivot bolt  128 , base plate  126 , upper housing shell  28 , lower housing shell  30 , etc., which would create a much larger tolerance stack-up and increase costs of fabrication and assembly. Preferably, the cam surface  148  could be located directly on connector  120  to further eliminate the tolerances associated with mount block  122 . 
         [0065]    Referring to  FIG. 10 , additional strip guiding features are disclosed. Not only should the integrated automated system have good control over the lancing site location as described above, it should also tightly control the location of the test strip fill channel  44 . To accomplish this, integrated device  10  has a carefully sized channel  110  that serves to guide test strip  42  from its load position down to the test site and locate it exactly with respect to the lancing site. During strip motion, channel  110  can even ensure that strip  42  is fully seated in its connector by gradually reducing lengthwise clearance along the travel path. Once strip  42  approaches the test position, its critical edge  108  can be spring-loaded to register against surface  112  inside cap  38  that tightly controls its location with respect to the lancet guide bore  60 . 
         [0066]    In the preferred embodiment shown, guide channel  110  and registration surface  112  for test strip  42 , guide bore  60  for lancet  46 , and a registration surface for contacting cam surface  148  on mount block  122  or connector  120 , are all molded into the same single part (protective cap  38 ). This allows tight control of the dimensional relationship between these features by reducing the tolerance stack-up between them and gives the best opportunity of ensuring that strip  42  will contact blood droplet  104 . 
       Variable Strip Approach Timing 
       [0067]    In order for the above-described strip approach to succeed, blood sample  104  should be present on the skin before strip  42  moves into position. Since human physiology varies such that it cannot be predicted exactly how long after lancing an appropriate-sized droplet will appear on the patient&#39;s skin, integrated device  10  preferably can be adjusted by the user to account for this variation. 
         [0068]    In the preferred embodiment of integrated device  10 , a processor-based electro-mechanical system controls the amount of time that elapses between firing of the lancet and the approach of test strip  42  to the test site. Patients who bleed easily can adjust this duration to be relatively short (for example 5 seconds) and those who bleed slowly can adjust it to be longer (for example 20 seconds.) Alternatively, a purely mechanical system for this adjustable delay may be used. 
         [0069]    This adjustability allows the total integrated device test time to be as quick as possible, not burdening all patients with a fixed wait time long enough for those who bleed slowly. 
       Strip Motion/Cap Removal Interlock 
       [0070]    Referring to  FIG. 11 , a cap removal interlock will be discussed. In order to protect the strip handling mechanism and ease changing of lancet  46 , strip  42  should be returned to its loading position before the user removes cap  38 . The preferred embodiment of integrated device  10  ensures this by combining strip return and cap removal into a single user-operated control. This control is a sliding button  40  that runs in an L-shaped slot  114 . To return strip  42  from the testing position to the load/unload position, the user slides button  40  along the long leg of L-slot  114 , as shown by arrow B. To remove cap  38 , the user slides button  40  along the long leg of L-slot  114  and then pushes it into the short leg of slot  114 . This way the user is forced to return strip  42  to the load/unload position before he can remove cap  38 . 
       Test Strip Ejection 
       [0071]    Traditional blood glucose testing utilizing a test strip  42  requires touching one end of strip  42  to the blood sample of interest. Once the test is complete, the bloodied test strip  42  needs to be disposed of. For health and safety reasons, it would be preferable not to require the user to handle used strips  42  after testing. Accordingly, a strip-eject mechanism can be employed on integrated device  10  that allows the user to remove a used strip  42  from device  10  without touching the strip. This mechanism can use pinch-rollers to drive strip  42 , a plunger to push strip  42  out of its connector, or similar well-known mechanism. 
       Overall Operation 
       [0072]    Referring mainly to  FIG. 1 , the overall operation of integrated device  10  to measure blood glucose will be described. The patient first pushes cap removal lever  40  over and up along L-shaped slot  114  to remove device cap  38 . If a used lancet  46  still remains in lancet holder  68 , ejection lever  36  is pushed downward to eject lancet  46  for disposal. Preferably the ejection mechanism is designed such that it cannot be actuated while device cap  38  is still in place. A fresh lancet  46  is inserted into lancet holder  68 , and lancet cap  51  is removed. Lancet holder  68  should be designed such that it provides a retention force that is greater than the force required to separate cap  51  from lancet  46 , so that lancet  46  is not pulled from lancet holder  68  when the patient tries to remove cap  51 . Device cap  38  is then reinstalled on device  10 . Alternately, cap aperture  54  and lancet cap  51 ,  78 ,  80  or  84  can be sized such that device cap  38  can be reinstalled before the lancet cap is removed from the lancet. 
         [0073]    The patient next removes a fresh test strip  42  from its desiccated vial and inserts the proper end into a mating connector (not shown) within slot  102  in device housing  26 . Preferably test strip  42  includes a conductive bar across an outer face such that the insertion of strip  42  powers on device  10 . Instructions guiding the patient through the testing process can be displayed on LCD  16 . Alternately, function button  12  can be used to turn on device  10 . 
         [0074]    With a fresh lancet  46  and test strip  42  loaded, integrated device  10  is cocked by pulling up on cocking collar  22 , and then placed over the test site on the patient, with recess  52  of cap  38  resting on the skin. Preferred testing sites include the forearm, upper arm, outer thigh, calf, and around the base of the thumb. Once device  10  is positioned, the patient presses actuator button  20  which causes lancet  46  to drive downward penetrating the skin and then retract. After a predetermined and preferably user-settable delay for allowing blood to emerge from the lancing site on the skin, test strip  42  is brought down along an arcuate path into contact with the blood sample. The patient holds device  10  in this position until device  10  emits an audible and/or visual indication that a sufficient amount of blood has been drawn into fill channel  44  of test strip  42  (detected by electrical measurements on strip  42 .) Device  10  then performs the appropriate measurements on the electrochemical process within test strip  42 , and when complete displays the result on LCD  16 . Further manipulation of data or settings can be performed by pressing function buttons  12  and  14 . 
         [0075]    After a test is complete, lever  40  is pushed towards the short leg of L-shaped slot  114  to return used strip  42  to the load/unload position outside of protective cap  38 . Strip  42  can then be removed from device  10  for disposal by pressing a strip eject lever or by manually removing strip  42 . Used lancet  46  can also be removed at this time for disposal, as previously described. 
       Control Solution Test Scheme 
       [0076]    Occasionally testing needs to be performed with a fresh test strip  42  and a “control solution” instead of blood to ensure that device  10  is calibrated and working properly. For this procedure, the patient uses function button  12  and/or  14  to indicate to device  10  that a control solution test will be performed. Cap  38  is removed, either before or after a fresh test strip  42  is inserted into device  10 . To avoid risk of accidental lancing, lancet  46  is preferably capped or removed during this process. With cap  38  out of the way and test strip  42  in the load/unload position, a drop of control solution can be applied to fill channel  44  of test strip  42 . This test proceeds much like the blood glucose test described above, but strip  42  is never moved from the load/unload position and lancet  46  is never fired. After the control solution test, test strip  42  is ejected and cap  38  is replaced. 
       Fill Channel Location Coding 
       [0077]    Referring to  FIG. 14 , a scheme for encoding test strips  42  with fill channel  44  location data is disclosed. In the manufacture of disposable test strips such as for testing blood glucose, it can be difficult to produce large quantities of strips  42  all having their fill channels  44  located a predetermined distance from an end of the strip  42  within a narrow tolerance. Since the blood samples  104  to be acquired by strips  42  are becoming quite small (e.g. 0.050 inches in diameter), a wide fill channel location tolerance can make it difficult or impossible for an integrated testing device to automatically align the test strip  42  with the blood droplet  44 . This problem can be solved by providing integrated device  10  with a motor or other prime mover to position the strip  42  longitudinally, and encoding the fill channel location for each strip  42  in a calibration code specific to that strip or batch of strips. When the calibration code is entered by the user or detected from strip  42  automatically, device  10  can then position the test strip  42  accordingly. 
         [0078]    Currently, many disposable test strips are sold with a code to calibrate the meter to the electrochemistry found on that particular test strip. This calibration code can be, for example, one of four numbers. If the fill channel location is characterized and similarly categorized as being within one of four possible ranges, it can be assigned one of four letters. The number and letter calibration codes can be merged together to form a 4 by 4 array. In this way, one of 16 different numbers can be used for each test strip, with each number uniquely identifying the electrochemistry calibration and fill channel location. 
         [0079]    As shown in  FIG. 14 , the user enters a calibration code, which includes positional data, via the user interface  150 . Microprocessor  152  then reads data from an EEPROM  154  which indicates how far to advance motor  156  to align fill channel  44  to the target droplet  104 . Home sensor  158  can be used to provide a location reference. 
       Shape Memory Alloy Firing Mechanism 
       [0080]    Referring to  FIG. 15 , an alternative method for firing lancing mechanism or strip delivery mechanism is disclosed. In the preferred embodiment of integrated device  10 , the lancing or plunger mechanism  91  (shown schematically in  FIG. 8 ) is cocked by pulling up on cocking collar  22 , and fired by pressing actuator button  20  (both shown in  FIG. 1 .) The test strip moving mechanism  160  (shown in  FIGS. 12 and 13 ), on the other hand, is not directly actuated by the user but is instead controlled by the device&#39;s microprocessor  152 , which ensures a suitable delay between lancet firing and test strip movement as described above. An electric solenoid can be employed between microprocessor  152  and release pin  138 , but given the typical force required to move pin  138 , the size of the solenoid and the batteries required to drive it is unwieldy. Since pin  138  does not need to be extracted with great speed, a motor and lead screw arrangement can be employed instead of a solenoid, but this introduces complexity, cost and reliability issues. To overcome the above drawbacks, a shape memory alloy (SMA) wire can be used to drive release pin  138 . 
         [0081]    In the preferred embodiment shown, a Nickel-Titanium alloy, know as Nitinol, is used in the shape of a wire  162 . At room temperature, a nitinol wire can easily be stretched 3-5% beyond its fabricated length. Upon heating the wire above a certain temperature threshhold, the wire will return to its fabricated length with some force. At the time test strip  42  is to be moved, microprocessor  152  on printed circuit board  164  initiates a current through anchor post  166 , which passes through wire  162  and returns to PCB  164  through a chassis ground. The current heats up Nitinol wire  162 , causing it to contract to its original length. The shortened length of wire  162  pulls release pin  138  in the direction of arrow C against the force of compression spring  168  located between base plate  126  and stepped shoulder  170  on pin  138 . When the end of pin  138  moves enough to disengage from hole  140  in pivot arm  124 , test strip moving mechanism  160  moves the test strip as previously described. When the current running through wire  162  is shut off, wire  162  cools and is again stretched by the compression spring  168 . This allows spring  168  to push pin  138  back out again (opposite the direction of arrow C) to engage pivot arm  124  when arm  124  is returned to the raised position. 
         [0082]    Ferules  172  or clamps are preferably crimped onto ends of wire  162  to provide attachment points. To vary the forces and contraction lengths achieved by Nitinol wire in a small space and to perhaps make electrical connections easier, each end of the wire can be connected to its own post  166  on PCB 164, and the wire can be run through a small, insulated pulley connected to the end of pin  138 . Additional pulleys or turning points can be attached or formed within the device housing. In another alternative embodiment, electrical connectivity can be provided to the wire by attaching electrical wires near the ends instead of passing the current through the anchor points. Shapes other than wire, such as a rod, bar, sheet or coil can be used. Nitinol or other shape memory alloys can be used to provide a tensile or compressive force to move pin  138 . Alternately, a piezoelectric material can be used. 
         [0083]    The preferred embodiment of integrated device  10  will have a specified operating temperature range, for example between 0 and 40 degrees Celsius. To ensure that wire  162  reaches the proper temperature to contract and operate the release mechanism properly when device  10  is anywhere within the specified temperature range, conventional control circuitry would always apply the maximum electrical current required to heat the wire from the bottom of the temperature range to the temperature required for wire contraction. However, device  10  would typically not be operated at the bottom of the predetermined operating range, so much of the current applied to wire  162  during each use would merely be drained from the device&#39;s batteries without providing any benefit. To overcome this drawback, device  10  should utilize a temperature sensor (which can also be used for other testing functions) and a current switching circuit that supplies only enough current to elevate wire  162  from the ambient temperature to the contracting temperature. Rather than supplying a constantly decaying current from a charged capacitor to wire  162 , the device&#39;s microprocessor can be configured to sense the ambient temperature and control a switch with one of its outputs to provide a series of pulses of current to wire  162  to cause its contraction. As ambient temperature decreases, the microprocessor provides pulses of longer duration, approaching a constant source of current as the ambient temperature approaches the bottom of the predetermined operating range. Alternatively, rather than pulsing the current, the duration of the current can be controlled based on the ambient temperature (i.e. a shorter duration for a higher ambient temperature.) By employing this inventive circuitry, smaller batteries can be used and/or longer battery life can be achieved, thereby making device  10  more compact and less expensive. 
         [0084]    The invention has been described with reference to various specific and preferred embodiments and techniques. However, it will be apparent to one of ordinary skill in the art that many variations and modifications may be made while remaining within the spirit and scope of the invention.

Technology Category: 1