Abstract:
A technique for efficiently sampling blood from body tissue by reducing pressure on the body tissue. In the present technique a body tissue is placed under reduced pressure to improve perfusion of blood in the body tissue before lancing. An embodiment of this apparatus includes a lancet carried by a piston slidable in a housing, a mechanism for transmitting mechanical energy internally in the apparatus for creating the reduced pressure on the body tissue. The apparatus also includes a driver that drives the lancet for lancing. The apparatus has a head in the housing for contacting the body tissue in an air-tight manner against suction forces. In the head facing the body tissue is a channel in which the air pressure can be reduced.

Description:
FIELD OF THE INVENTION 
     The present invention is related to techniques for lancing skin tissue with a lancet and drawing blood from it and more particularly to apparatuses and methods for lancing skin tissue to obtain an adequate sample with less pain. 
     BACKGROUND 
     The analysis and quantification of blood components is an important diagnostic tool for better understanding the physical condition of a patient. Since adequate noninvasive blood analysis technology is not currently available, blood samples still need to be obtained and analyzed by invasive methods from a great number of patients every day. A well known example of such needs is self monitoring of glucose levels by a diabetic individual, often performed in the home of the individual. To obtain a blood sample it is necessary to puncture the skin with a sharp object such as a lancet at a region well supplied with blood vessels, for example, the fingertip. For lancing, a lancet launcher is first loaded with a lancet and cocked by pulling or rotating the cap on the launcher. The tip of the launcher is then pressed against the skin and a button is pressed to launch the lancet to strike the skin. 
     Currently available lancet launchers are typically pen-shaped devices. The lancet is held in a cylindrical piston which is propelled by a spring mechanism. On cocking, the spring serves to store the energy required to propel the piston forward at the skin. The propulsion of the lancet causes the lancet to impact against and puncture the skin, causing a wound large enough for sampling blood. 
     Such blood sampling is often painful and inconvenient. As a result, many patients tend to not sample blood as frequently as suggested by the health professionals to monitor the physiological functions adequately. Moreover, for fear of pain in blood sampling, many patients fail to use the lancet launchers properly. Such improper use results in inadequate blood volume being collected and requires repeating the lancing procedure, causing more pain and multiple wounds. 
     What is needed is a lancet launcher for sampling blood that can be used for sampling blood efficiently, so as to minimize pain to encourage a patient to follow a routine for sampling blood as directed by health professionals. 
     SUMMARY 
     In the present invention, the sampling of blood from body tissue is facilitated by applying a negative pressure to the body tissue before and while a lancet is launched to inflict a bleeding wound in the body tissue. This negative pressure is mechanically transmitted internally through substantially the body of the lancet device. In this way, there is no cumbersome suction source attached to the front part of the lancet device to hinder convenient application of the lancet device to the body tissue. 
     In one aspect, the present invention provides an apparatus having a lancet for sampling blood from body tissue. An embodiment of this apparatus includes a lancet, a housing, and a driver that drives the lancet for lancing. The lancing of the body tissue by the lancet results in a wound for bleeding. The housing is operatively connected to the lancet and shields it before lancing. The housing has a head for contacting the body tissue in an air-tight manner against vacuuming (i.e., suction) forces and having a channel in which the air pressure can be reduced before the lancet is driven to lance the body tissue. As an example, a piston can be included in the channel for air-tight sliding movement against the channel wall along the housing. Mechanical energy is transmitted via the piston from near the rear of the lancet device to near the head to result in reduced air pressure. In one embodiment, a rearward movement of piston in the channel can cause the air pressure in the channel near the head to be reduced before lancing. In another embodiment, withdrawing air through a bore in the piston from the front to the back of the piston while the front of the channel is sealed by the body tissue allows the piston to slide forward to drive the lancet toward the body tissue as the air pressure is reduced at where the lancet device contacts the body tissue. 
     Currently, finger-prick devices do not provide enough blood for certain tests that require larger volumes. Often large and multiple wounds are required. For example, some patients, such as infants, have veins that are difficult to locate for sampling through an intravenous needle. In these patients the device of the present invention can provide larger volumes for a smaller puncture wound. Also, using the present apparatus, by reducing the environmental pressure on the body tissue to increase its blood perfusion, the depth of penetration by the lancet into the body tissue can be reduced to provide an adequate blood sample. With a smaller penetration depth, the trauma and pain of overpenetration is avoided. Such reduction of discomfort and tissue damage can significantly improve the willingness of patients to comply with, for example, a blood sampling routine. The compact designs of the present lancet devices allow the lancet devices to be conveniently maneuvered without clustering around the lancing location on the body tissue. This is significant for the precise positioning of the lancet device on a desired location on the skin and one-handed operation by a patient who may have lost substantial dexterity due to a chronic illness. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following figures are included to better illustrate the embodiments of the apparatus and technique of the present invention. In these figures, like numerals represent like features in the several views. 
     FIG. 1 shows in sectional view an embodiment of an apparatus of the present invention. 
     FIG. 2 show an exploded sectional view in portion of the embodiment of the apparatus of FIG.  1 . 
     FIG. 3 shows the penetration into a body tissue by a lancet of an embodiment of a lancing apparatus of the present invention. 
     FIG. 4A shows a sectional view in portion of the front part of a lancing apparatus of the present invention. 
     FIG. 4B shows sectional view in portion of the front part of yet another lancing apparatus of the present invention. 
     FIG. 5 shows an embodiment of an electrical driving mechanism associated with a lancing apparatus for effecting a reduced pressure on the body tissue. 
     FIG. 6 is a schematic representation that shows an embodiment of an apparatus including an external suction source associated with the lancet launcher. 
     FIG. 7 shows a schematic sectional view of an embodiment with a piston having a bore for transmitting suction. 
     FIG. 8 shows a schematic sectional view of the embodiment of FIG. 7 where the lancet is driven forward. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In one aspect, the present invention provides a technique for obtaining an adequate amount of blood by puncturing body tissue while applying a negative pressure to a body tissue to cause bleeding in the body tissue. A bleeding wound can be created by using a lancet. As used herein, a “lancet” is a shaft of any shape having a sharp point or edge for cutting, puncturing, or incising tissue, e.g., by including a blade, pin, needle, or the like. 
     FIG. 1 shows a sectional view of an embodiment of an apparatus for sampling blood from a body tissue (e.g., skin) according to the present invention. FIG. 2 shows an exploded sectional view in portion of the embodiment of FIG.  1 . For the sake of clarity of depiction, the lower part of the body  104  (as viewed by the viewer of the figure) is not shown in FIG.  2 . In FIG. 1, the apparatus (i.e., lancet launcher)  100  includes a body  104  and a head (or end cap)  106 . The head  106  is connected by screw threads  108  to the front part  110  of the body  104  such that by turning the head  106  relative to the body  104 , the head  106  can be moved more towards the front or towards the back of the body  104 . As used herein, the terms “front,” “forward,” and “distal” refer to a position or direction that is towards the end where the lancet is. Therefore, these terms (“front, forward, distal,” etc.) refer to a position that is near the body tissue to be punctured when the lancet device is applied to lance the body tissue. The terms “back,” “rear,” “backward,” and “proximal” refer to a position or direction that is away from the body tissue to be punctured. The screw threads  108  that connect the head  106  to the body  104  are adequately tight such that air cannot leak through in the normal operation of the device. 
     As seen in FIG.  1  and FIG. 2, the body  104  has a shell  109  encircling a channel (or lumen)  112  which extends backward from the body&#39;s front part  110 . A piston  114  can slide against the wall of the channel  112  in an air-tight manner (i.e., there is no substantial leak of air between the cylindrical surface of the piston and the wall of the channel  112  in the shell  109 ). Preferably the interface between the piston  114  and the channel inside wall (or Luminal wall)  116  is such that there is little friction hindering the sliding motion of the piston in the channel  112 . To this end, the piston  114  and the channel inside wall  116  can be made or coated with a low friction material, such as polytetrafluoroethylene. Optionally the interface between the piston  114  and the channel inside wall  116  can be lubricated and sealed against air leak by a liquid lubricant. Low friction materials and lubricants are known in the art and a person skilled in the art will be able to select such materials and lubricants based on the present disclosure. 
     The distal portion of the piston  114  has a cavity  120  in which a lancet block  122  is snugly secured. The lancet block  122  has a lancet  124  at its distal end. When the piston  114  slides distally forward, the piston  114  pushes the lancet block  122 , and therefore the lancet  124 , forward to lance the body tissue. 
     The body  104  of the apparatus, further has a hollow cylinder  126  extending backward and encircling a stem  128  which is rigidly, preferably integrally, connected to the piston  114 . The stem  128  has a shaft  130  extending backward and through a back flange  132  to connect to a sleeve cap  134  which has a cylindrical sleeve  136  encircling the shaft  130  and the back portion of the cylinder  126 . An actuating spring  140  is positioned between the stem  128  and the back flange  132  such that when the piston is moved backward it causes the stem  128  to compress the actuating spring  140  on the back flange  132 . The stem  128  has a cantilever  142  extending distally and is pushed away from the stem  128  towards the channel wall  116  by a spring  144  situated between the cantilever  142  and the stem  128 . The mid-portion  146  of the shell  109  has a well  148 A. When the piston  114  is moved (or pulled) backward adequately, a finger catch  150  of the cantilever  142  is pushed into the well  148 A. When the backwardly pulling force is terminated, the compressed actuating spring  140  urges the stem  128  forward and the finger catch  150  catches on the wall  148 B of the well  148 A and is retained. 
     A triggering button  152  is situated in the well  148 A above the finger catch  150 . Normally the triggering button  152  is urged away from the axis of the channel  112  by a button spring  154 . When the triggering button  152  is pushed towards the axis of the channel  112 , it dislodges the finger catch  150  from the wall  148 B of the well  148 A. As a result, the actuating spring  140  drives the stem  128 , and therefore the lancet  124 , forward towards the body tissue for lancing. 
     The head  106  also has a channel  156  which is connected to the channel  112  of the body  104  in an air-tight fashion. The head  106  further has a distal ring-shaped ridge  158  encircling a depression  160 , which joins by a pore  162  to the proximal portion of the head channel  156 . The distal end of the ridge  158  when pressed against the body tissue seals to prevent air leakage such that when the piston  114  is pulled backward the void volume in the head channel  156  is increased, thereby reducing the air pressure therein to a pressure less than that of the ambient pressure, i.e., the air pressure external to the head  106 . Due to the reduced pressure, blood perfusion in the body tissue against the depression  160  is increased. 
     While the body tissue facing the depression  160  is still under negative pressure (i.e., under a pressure less than that of the ambient pressure), the trigger button  152  is pressed to release the finger catch  150  from the well  148 A, thereby driving the lancet forward. Due to its flexibility, when the body tissue  164  is pressed against the ridge  158  the body tissue will extend into the depression  160 . Preferably, the depression is made deep enough that it is not necessary for the lancet to extend all the way past the distal end of the ridge  158  for lancing to result in a puncture wound deep enough for blood sampling (see FIG.  3 ). In this way, the ring-shaped ridge  158  will help to prevent inadvertent injuries to the patient (or user) by an exposed lancet. 
     Preferably, the head  106  is snugly but detachably connected to the shell  109 . As shown in FIG. 4A, the head  106  can be connected by screw-threads with the shell  109  in an air-tight manner. By adjusting the position of the head  106  on the shell  109 , the distance that the lancet  124  when launched can extend past the pore  162  can be adjusted. In an apparatus shown in FIG. 4B, the head  106  is held in an air-tight manner by friction on an intermediate sleeve  165 , which is threadedly (i.e., by screw-threads) connected to the shell  109 . After use, the head  106  can be conveniently detached by pulling from the sleeve  165 . 
     Driving Mechanisms 
     A wide variety of energy sources can be used for creating the negative pressure and for driving the lancet. The mechanical piston, catch and spring mechanism described above and shown in FIG. 1 is suitable for manual operation by an individual. As an alternative, shown in FIG. 5, the piston  114  (as that of in FIG. 1) can be pulled backward by an electric motor  166  by means of a cord  168  on a spool  170  to cock the stem  128  against the spring  140  (as those of FIG. 1) and create the negative pressure. A trigger  172  can be used to initiate the backward pulling of piston  114  by the motor  166 . The motor  166  can either be activated by alternate current or by direct current, such as using batteries. Further, electronics can be included in the lancing apparatus such that once the trigger is actuated, (e.g., after the piston  114  has been pulled back to result in reduced pressure, and an adequate distance has been reached) the piston  114  will be suddenly released and allow the forward driving force (e.g. from the driving spring  140 ) to launch the lancet forward for lancing. Such electronics can be enclosed, for example, are the motor region or in the housing of the lancing apparatus. Electronics that can perform these functions in within the skill of one skilled in the art. 
     Furthermore, separate mechanisms can be used for creating the negative pressure and independently for driving the lancet. For example, as illustrated in FIG. 6, a vacuum (or suction) source  174  can be connected to the channel (similar to channel  156  of FIG. 1) of the lancing apparatus  176 . With the skin tissue  164  under negative pressure, the lancet can be driven, e.g., by the spring mechanism (similar to spring  140  of FIG. 1) toward to the skin tissue for lancing. Additionally, the lancet can further be driven mechanically, electrically, pneumatically, or hydraulically. Such mechanisms for driving a shaft forward are known in the art and can be adopted to apply in the present lancing technique by one skilled in the art. 
     Using Vacuum (Suction) for Increasing Perfusion and Driving the Lancet 
     In another aspect, the present invention provides a technique for using vacuum (i.e., suction) to increase perfusion of a body tissue and drive the lancet to puncture (or incise, cut, etc.) the body tissue simultaneously. FIG. 7 shows an embodiment that has this advantage. 
     In FIG. 7, a blood sampling apparatus  170  has a body  172  attached to a driver head  174 . The body  172  includes a tubular shell  176  in which a piston  178  can freely slide. A flexible diaphragm  179  separates the body  172  and the driver head  174  in an air-tight fashion. A vacuuming port (i.e., suction port)  180  provides access to a suction source (or vacuum source, arrow AR indicates the direction of gas flow to the suction source V). A bore (or passage)  181  in the piston  178  allows air to pass therethrough and the air pressure on the two sides of the piston  178  to equilibrate. The piston  178  is rigidly supported from the diaphragm  179  by rod  182  such that movement of the diaphragm  179  will cause the piston  178  to move. The void area inside the tubular shell  176  between the piston  178  and the diaphragm  179  forms a chamber  184 . When a body tissue (such as the flesh of a finger)  186  seals the end  188  of the tubular shell  176  distal from the diaphragm  179 , a chamber  190 , bordered by the body tissue  186 , a distal portion of the shell  176 , and the piston  178 , results. The piston  178  holds a lancet  194  at an end (the distal end) opposite to the driver head  174 . 
     The driver head  174  has an air-tight cap  196 , which has an openable vent  198  to allow air pressure to equilibrate between the atmosphere external to apparatus  170  and a chamber  202  inside the driver head  174 . A resilient support  204  (such as compressible object, e.g., a resilient bead or a spring) extends from the diaphragm  179  to the end of the cap  196  on the side of the driver head  174  opposite to the diaphragm  179 . The compressible bead can be made with a resilient material such as a polymeric substance. Further, the compressible bead can be solid or a bladder filled with a fluid, such as a gas or a liquid. 
     In operation, as shown in FIG. 8, a suction pulse (can be referred to as a “vacuum pulse”) of a predetermined duration and amplitude is applied to the suction port  180 . The negative pressure is transmitted to the chamber  184 , and through the bore  181  to the chamber  190 . The negative pressure in the chamber  184  causes the diaphragm  179  to flex forward (i.e., towards the lancet  194 ), thereby extending the resilient support  204 . This forward extension of the diaphragm  179  causes the piston  178  to move a finite distance. The negative pressure communicated through the bore  181  to the chamber  190  causes the tissue to be sucked against the forward end  188  of the tubular shell  176  and increases the blood flow to that tissue. The simultaneous movement of the advancing lancet and the suction on the tissue against the tubular shell  176  drives the needle  194  to puncture the tissue of the finger  186 , thereby causing bleeding from the puncture wound. Thus, blood  210  is emitted from the lancing wound and is sampled from the finger tissue by the application of suction. The suction source provides the driving force for driving the lancet  194 , as well as providing the reduced environmental pressure on the tissue to increase blood flow and bleeding. The removal of the suction restores the piston  178  to its original position of FIG.  7 . 
     Although preferred embodiments of the present invention have been described and illustrated in detail, it is to be understood that a person skilled in the art can make modifications within the scope of the invention.