Patent Publication Number: US-2007112281-A1

Title: Cap with revolving body for a dermal tissue lancing device

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates, in general, to medical devices and, in particular, to caps for dermal tissue lancing devices and associated methods.  
      2. Description of the Related Art  
      Conventional dermal tissue lancing devices generally have a rigid housing and a lancet that can be armed and launched so as to briefly protrude from one end of the lancing device. For example, conventional lancing devices can include a lancet that is mounted within a rigid housing such that the lancet is movable relative to the rigid housing along a longitudinal axis thereof. Typically, the lancet is spring loaded and launched, upon release of the spring, to penetrate (i.e., “lance”) a target site (e.g., a dermal tissue target site on a user&#39;s fingertip). A biological fluid sample (e.g., a whole blood sample) can then be expressed from the penetrated target site for collection and analysis. Conventional lancing devices are described in U.S. Pat. No. 5,730,753 to Morita, U.S. Pat. No. 6,045,567 to Taylor et al. and U.S. Pat. No. 6,071,250 to Douglas et al., each of which is incorporated fully herein by reference.  
      Dermal tissue lancing devices often include a cap that engages the target site. Such a cap typically has an aperture (i.e., opening), through which the lancet protrudes, and a distal end of the cap will be placed in contact with the target site during use.  
      When a cap is contacted with a target site, pressure is usually applied to the target site prior to launch of the lancet. This pressure urges the cap against the target site and creates a target site bulge within the opening of the cap. The lancet is then launched to penetrate the target site bulge. A fluid sample, typically blood, is then expressed from the lanced target site for testing. For example, a blood sample expressed from a lanced dermal tissue target site may be tested for the analyte glucose.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings in which like numerals indicate like elements, objects and forces, of which:  
       FIG. 1  is a simplified perspective view of a cap for use with a dermal tissue lancing device according to an exemplary embodiment of the present invention;  
       FIG. 2  is a simplified exploded perspective view of the cap of FIG. A;  
       FIG. 3  is a simplified perspective, partially-cut-away view of the cap of  FIG. 1 ;  
       FIG. 4  is a simplified, perspective, partially-cut-away view of the cap of  FIG. 1A  urged against a dermal tissue target site;  
       FIG. 5  is a simplified perspective view of a cap for a dermal tissue lancing device cap according to another exemplary embodiment of the present invention;  
       FIG. 6  is a simplified top view of the cap of  FIG. 5 ;  
       FIG. 7  is a simplified, perspective, partially-cut-away view of the cap of  FIG. 5  with a dashed line depicting a circular axis of the cap&#39;s cap body;  
       FIG. 8  is a simplified perspective, partially-cut-away view of the cap of  FIG. 5  urged against a dermal tissue target site;  
       FIG. 9  is a flow diagram illustrating a sequence of steps in a process according to an exemplary embodiment of the present invention; and  
       FIGS. 10A, 10B  and  10 C are perspective, partially-cut-away views depicting various stages of the process of  FIG. 9 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       FIG. 1  is a simplified perspective view of a cap  100  for use with a dermal tissue lancing device (not shown) according to an exemplary embodiment of the present invention.  FIGS. 2 and 3  are a simplified exploded perspective view and a simplified perspective, partially-cut-away view of cap  100 , respectively.  FIG. 4  is a simplified, perspective, partially-cut-away view of cap  100  urged against a dermal tissue target site TS such that a target site bulge (B) has been formed.  
      Referring to  FIGS. 1-4 , cap  100  includes a retainer  102 , a generally ring-shaped segmented cap body  104  and a spring  106 . Retainer  102  includes an inner retainer portion  108 , an outer retainer portion  110  and an opening  112  along a longitudinal axis A-A (see  FIG. 2 ) of cap  100 . Retainer  102  has a proximal end  114  configured for engagement with the dermal tissue lancing device (not shown) and a distal end  116 . Furthermore, inner retainer portion  108  includes cap body engagement features  118  and outer retainer portion  110  includes a lip  119 .  
      Proximal end  114  is configured for engagement with the dermal tissue lancing device. For example, proximal end  114  can be removeably attached to an end of a suitably modified conventional lancing device by slideably mounting, snap-fitting or screw-fitting proximal end  114  to the end of the dermal tissue lancing device. One skilled in the art can readily modify suitable conventional dermal tissue lancing devices for engagement with a proximal end of caps according to embodiments of the present invention. Suitable conventional dermal tissue lancing devices are described in, for example, U.S. Pat. Nos. 5,730,753, 6,045,567 and 6,071,250, each of which is hereby incorporated in full by reference.  
      However, once apprised of the present invention, one skilled in the art will appreciate that caps according to embodiments of the present invention are not limited to use with the dermal tissue lancing devices described in the aforementioned patents. Rather, caps according to embodiments of the present invention can be used with any suitable dermal tissue lancing device including, for example, those that employ lancets, hollow needles, solid needles, micro-needles, ultrasonic devices, thermal techniques, and any other suitable technique for extraction of a bodily fluid sample from a dermal tissue target site. In addition, the dermal tissue lancing device can, if desired, include an integrated analytical system for the determination of an analyte (e.g., glucose) in an expressed bodily fluid sample.  
      Each of the segments of ring-shaped segmented cap body  104  (i.e., cap body segments  122  noted below), includes a distal compression surface  120 , borders opening  112  and is revolvingly engaged with a cap body engagement feature  118  and securely engaged with lip  119 . Ring-shaped segmented cap body  104  includes a plurality of cap body segments  122  (namely eight cap body segments  122 ), an outer recess  124 , and an inner recess  126 . In addition, ring-shaped segmented cap body  104  includes a plurality of dermal tissue engagement features  127  (also referred to as “ridges”  127 ) on distal compression surface  120 . Although, for the purpose of explanation only, eight cap body segments are depicted in the ring-shaped segmented cap body of  FIGS. 1-4 , any suitable number of cap body segments can be employed.  
      Ridges  127  serve to enhance purchase between cap body distal compression surface  120  and a dermal tissue target site. Such enhanced purchase can also be achieved, for example, by forming ring-shaped segmented cap body  104  of a material that is suitably tacky and/or a material that has a suitable high coefficient of friction. An example of such a material is a silica-filled silicone elastomer. Furthermore, enhanced purchase can be achieved via a roughened distal compression surface or a distal compression surface with recesses.  
      Ring-shaped segmented cap body  104  can be formed of any suitable material including, but not limited to, rigid materials, elastomeric materials, polymeric materials, polyurethane materials, latex materials, silicone materials and combinations thereof. It should be noted that the segmented nature of ring-shaped segmented cap body  104  provides for each cap body segment  122  to revolve about cap body engagement features  118  independently of any other cap body segment and regardless of whether the cap body segments are formed of a rigid or deformable material.  
       FIGS. 3 and 4  depict the manner in which outer recess  124  of ring-shaped segmented cap body  104  provides for secure engagement with lip  119  of outer retainer portion  110  and inner recess  126  of ring-shaped segmented cap body  104  for secure yet revolving engagement with cap body engagement features  118  of inner retainer portion  108 .  
      As is explained in further detail herein, when a force is exerted on distal compression surface  120  by the urging of cap  100  against a dermal tissue target site, at least a portion of the ring-shaped segmented cap body  104  revolves while ring-shaped segmented cap body  104  remains securely engaged within outer retainer portion  110  by lip  119 . This revolution is evident from a comparison of the relative locations of ring-shaped segmented body  104  in  FIGS. 3 and 4 . The revolution occurs essentially about the circular axis of ring-shaped segmented cap body  104 , i.e., about cap body engagement features  118 .  
      Cap body segments  122  essentially rest on cap body engagement features  118  and can revolve thereon. Ring-shaped segmented cap body  104  has a generally C-shaped cross-section (see  FIGS. 3 and 4 ). Once apprised of the present disclosure, one skilled in the art will recognize that although ring-shaped segmented cap body  104  can be generally described as “ring-shaped,” such a shape refers to the overall shape of the plurality of cap body segments  122  (each with an inner recess  126 , an outer recess  124  and ridges  127 ). Such a ring-shape can also be generally considered a “toroid” shape or a “doughnut” shape.  
      Opening  112  can have any suitable cross-sectional shape(s) in a direction perpendicular to longitudinal axis A-A including, but not limited to, circular, square, hexagonal, octagonal and triangular cross-sectional shapes. In addition, the cross-section shape can be such that access to opening  112  by, for example, a test strip is provided. Such test strip access enables beneficial in-situ transfer of a blood sample to the test strip as described in U.S. patent application Ser. No. 10/143,399 (published as US 2003/0143113 A2 on Jul. 31, 2003 and hereby incorporated in full by reference), International Application No. PCT/US01/07169 (published as WO 01/64105 A1 on Sep. 7, 2001) and International Application No. PCT/GB02/03772 (published as WO 03/015627 A2 on Feb. 27, 2003).  
      Referring to  FIGS. 3 and 4 , as cap  100  is urged against a dermal tissue target site by application of force F 1 , ridges  127  engage the dermal tissue target site. As F 1  increases, spring  106  is depressed due to longitudinal relative movement of inner and outer retainers portions  108  and  110  (compare  FIGS. 3 and 4 ). The urging of cap  100  against dermal tissue target site TS results in a torsional force being applied to ring-shaped segmented cap body  104  that results in revolution (i.e., rotation) of ring-shaped segmented cap body  104 ,(namely cap body segments  122 ) about cap body engagement features  118 . This revolution is inward with respect to opening  112 .  
      During this inward revolution/rotation, ridges  127  and distal compression surface  120  further engage the dermal tissue target site and form a target site bulge B within opening  112  (see  FIG. 4 ). Continued application of force F 1  to the dermal tissue target site increases pressure within target site bulge B and, following lancing of target site bulge B, facilitates expressions of bodily fluid (e.g., blood) out of the lanced target site without additional manual manipulation of the lanced target site.  
      To increase bodily fluid expression, the applied force can be maintained for a predetermined time period (i.e., a post-lance pressure time period) after lancing (e.g., a post-lance pressure time period in the range of about 2 seconds to about 12 seconds). The amount of expressed bodily fluid can also be increased by also applying and maintaining force prior to lancing (i.e., pre-lance pressure) for a predetermined time period, for example, in the range of 1 seconds to 8 seconds and typically in the range between about 3 seconds and 5 seconds.  
       FIG. 5  is a simplified perspective view of a cap  200  for a dermal tissue lancing device cap (not shown) according to another exemplary embodiment of the present invention.  FIGS. 6 and 7  are a simplified exploded perspective view and a simplified perspective, partially-cut-away view of cap  200 , respectively.  FIG. 8  is a simplified, perspective, partially-cut-away view of cap  200  urged against a dermal tissue target site TS such that a target site bulge (B) has been formed.  
      Referring to  FIGS. 5-8 , cap  200  includes a retainer  202  and a generally ring-shaped deformable cap body  204 . Retainer  202  includes an opening  212  along the longitudinal axis of cap  200 . Retainer  202  has a proximal end  214  configured for engagement with the dermal tissue lancing device (not shown) and a distal end  216 . Furthermore, retainer portion  202  includes a lip  219 .  
      Ring-shaped deformable cap body  204 , including a distal compression surface  220 , borders opening  212  and is revolvingly engaged with retainer  202 . Ring-shaped deformable cap body  204  includes further a plurality of slits  222 , an outer recess  224 , and an inner recess  226 . In addition, ring-shaped deformable cap body  204  includes a plurality of dermal tissue engagement features  227  (also referred to as “ridges”  227 ) on distal compression surface  220 .  
       FIGS. 7 and 8  depict the manner in which outer recess  224  of ring-shaped deformable cap body  204  provides for secure engagement with retainer-lip  219  while providing for ring-shaped deformable cap body  204  to revolve (i.e., rotate inward) during use (as is evident from a comparison of the position of ring-shaped deformable cap body  204  in  FIGS. 7 and 8 ).  
      As is explained in further detail herein, when a force is exerted on distal compression surface  220  by the urging of cap  200  against a dermal tissue target site, at least a portion of the ring-shaped deformable cap body  204  revolves while ring-shaped deformable cap body  204  remains securely engaged within retainer  202 . The revolution occurs essentially about the circular axis of ring-shaped deformable body  204 . Such revolution can be likened to a rotational flexing of the ring-shaped deformable cap body.  
      Referring to  FIGS. 7 and 8 , as cap  200  is urged against a dermal tissue target site by application of force F 2 , ridges  227  engage the dermal tissue target site. The urging of cap  200  against dermal tissue target site TS (and a radially outward retaining effect of retainer  202 ) results in a torsional force being applied to ring-shaped deformable cap body  204  that causes revolution (i.e., rotation) of ring-shaped deformable cap body  204  inward with respect to opening  212 . Slits  222  and inner recess  226  facilitate such revolution while retainer  202  serves to limit radially outward movement of ring-shaped deformable cap body  204 .  
      During this inward revolution/rotation, ridges  227  and distal compression surface  220  further engage the dermal tissue target site and form a target site bulge B within opening  212  (see  FIG. 8 ). Continued application of force F 2  to the dermal tissue target site increases pressure within target site bulge B and, following lancing of target site bulge B, facilitates expressions of bodily fluid (e.g., blood) out of the lanced target site without additional manual manipulation of the lanced target site.  
      During use, there is a potential for dermal tissue lancing device caps to come into contact with blood or other bodily fluid. Such contact could conceivably lead to contamination of the cap with micro-organisms (e.g., bacteria or fungi) or viruses of undesirable activity. However, caps according to embodiments of the present invention can be optionally formed, at least partially, of a suitable anti-microbial material, anti-fungal material and/or anti-viral material that serves to alleviate the undesirable activity of such micro-organisms or viruses. Such a suitable material can be, for example, an anti-microbial plastic, anti-microbial resin and/or anti-microbial silicone. Suitable anti-microbial materials can include, for example, anti-microbial compounds with a trichloro-phenol group, such as 2,4,4-trichloro-2-hydroxy diphenol ether. The anti-microbial compound can be, for example, a coating of the cap or incorporated directly in the cap.  
      Based on the description of caps  100  and  200  above, one skilled in the art will recognize that caps according to embodiments of the present invention generally include a retainer and a ring-shaped cap body (such as, a ring-shaped deformable cap body or a ring-shaped segmented cap body). Moreover, the retainer has a proximal end configured for engagement with the dermal tissue lancing device, a distal end with a cap body engagement feature (such as a lip) and an opening. In addition, the ring-shaped cap body has a distal compression surface, borders the opening and is securely and revolvingly engaged with the cap body engagement feature. Also, when a force is exerted on the distal compression surface during use of the cap, the ring-shaped cap body revolves (e.g., inward with respect to the opening) while remaining securely engaged with the retainer.  
       FIG. 9  is a flow chart illustrating a sequence of steps in a process  300  for lancing a dermal tissue target site TS using a cap with a revolving cap body.  FIGS. 10A through 10C  are simplified cross-sectional views depicting various stages of the process of  FIG. 9 . For illustrative purposes, cap  100  of  FIG. 1  is depicted in FIGS.  10 A- 10 C as being employed in process  300 . However, one skilled in the art will recognize that any cap for a dermal tissue lancing device according to the present invention can be employed in methods for lancing a dermal tissue target site according to the present invention. In this regard, it should be noted that any functional behavior or use of caps for dermal tissue lancing devices according to embodiments of the present invention as described herein can be included in methods for lancing a dermal tissue target site according to the present invention. Moreover, one skilled in the art will recognize that  FIGS. 10A through 10C  depict only a portion X of a dermal tissue lancing device with portion X including a lancet L.  
      Process  300  includes for contacting a distal compression surface  120  of a ring-shaped segmented cap body  104  of a dermal tissue lancing device cap  100  with the dermal tissue target site TS (see step  310  of  FIG. 9 , with  FIG. 10A  depicting dermal tissue lancing device cap  100  prior to use). Although, for the purpose of explanation only, process  300  is described in conjunction with a ring-shaped segmented cap body, processes according to embodiments of the present invention can generally employ any suitable ring-shaped cap body including, for example, ring-shaped deformable cap body  204 .  
      The dermal tissue lancing device cap  100  is then urged towards the dermal tissue target site TS, such that a force is exerted on the distal compression surface  120  that results in the ring-shaped segmented cap body  104  revolving while remaining securely engaged within a retainer (i.e., retainer inner and outer portions  108  and  110 , respectively) of the dermal tissue lancing device cap  100 . See step  320  of  FIG. 9  and  FIG. 10B .  
      Subsequently, a target site bulge B of the dermal tissue target site TS is lanced with lancet L of the dermal tissue lancing device, as set forth in step  330  of  FIG. 9  and as illustrated in  FIG. 10C .  
     EXAMPLE  
     Comparative Cap Success Rate and Subjective Discomfort  
      A comparative study between a cap for a dermal tissue lancing device according to an embodiment of the present invention (i.e., cap  200  of  FIGS. 5, 6 ,  7  and  8 ) and a conventional rigid cap was conducted using a 28-gauge lancet available from Becton Dickinson of Franklin Lakes, N.J.  
      The method of testing comprised pressing the cap body (fitted onto the distal end of a conventional lancing device) against a dermal tissue target site of a subject&#39;s finger for 3 seconds, lancing the dermal tissue target site with a 28-gauge needle, continuing to hold the cap against the dermal tissue target site for 10 seconds, removing the cap from the dermal tissue target site and collecting blood from the lanced dermal tissue target site with a calibrated glass capillary pipette.  
      During the lancing step, the subjects rated the amount of discomfort experienced using a subjective scale ranging from 0 to 10. In this subjective scale, a rating of 0 indicated that the subject did not feel any pain during lancing and a rating of 10 indicating that lancing was very painful to the subject. The average subjective score for cap  500  was 2.5 versus 4.3 for the rigid cap. This score indicates that the level of discomfort associated with use of cap  200  is relatively low.  
      Success was defined as obtaining at least 0.7 microliters of blood (i.e., typically the minimum volume required to give an accurate assessment of an analyte, such as glucose, in blood with hand-held devices). Percent success rate is given for all cap designs tested in Table I below (where n is the number of subjects tested).  
                           TABLE 1                               Subjective   % Success           Volume, uL   Discomfort   Rate ≧       Pressure Caps   Mean ± SD   Mean ± SD   0.7 uL                                                Cap 200 (n = 36)   2.1 ± 1.4   2.5 ± 1.7   89       Rigid Cap (n = 36)   0.0 ± 0.0   4.2 ± 2.0   0                  
 
      The data in Table I indicate a significant percent success rate with cap  200  when compared to the rigid cap. Since the dermal tissue target sites were not physically manipulated (other than by the caps themselves as described above) to enhance blood expression, the success rate indicates that caps according to embodiments of the present invention do not require physical manipulation for blood expression.  
      It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.