Abstract:
A disposable blood sampling device wherein inner and outer spaced apart pad members, separated by a compressible pad-bridging enclosure respectively carry an axially extending evacuated collecting container closed by a penetrable end cap and an axially aligned, double-ended cannula. In normal position the cannula is maintained in withdrawn position within the enclosure. The cannula is prevented from penetrating the cap of the collecting tube when the outer member is depressed toward the inner member until after penetration of the epidermis has occurred.

Description:
This application is directed to disposable blood collection devices and more particularly to a system designed for self use at home. 
     BACKGROUND OF THE INVENTION 
     A number of diagnostic procedures can now be performed by the patients at home utilizing relatively small quantities of blood which can be conveniently obtained from capillary blood sources such as a fingertip. While various blood sampling devices have been proposed and are in use, most of them, as exemplified by the following listed patents, are of the type which draw venous blood from patients in a procedure which should be performed by a trained medical technologist: 
     
         ______________________________________3,200,813   Christakis   4,256,120 Finley3,536,061   Ogle         4,298,011 Mangurten et al3,545,427   Ryan         4,409,990 Mileikowsky4,024,857   Blecher et al                4,418,703 Hoch et al4,155,350   Percarpio    4,449,529 Burns et al4,215,700   Crouther et al______________________________________ 
    
     While not all of the foregoing patents are directed to devices which accumulate venous blood, none have been sufficiently versatile to accomplish all of the objects of the present invention. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a micro-blood collection device which accumulates the blood flow from a skin or epidermal puncture in a sterile sampler container in a manner which insures that the skin puncture will occur before the double-ended cannula penetrates a cap sealing an evacuated collection chamber. 
     Still another object of the invention is to provide a blood sampling device of the character described in which the depth of penetration of the double-ended cannula into the tip of the finger, or other selected part of the body, is reliably controlled. 
     A further object of the invention is to provide a blood sampling device having a box-like housing which hides the double-ended needle from view, and thus reduces the trauma involved in this self-testing procedure. 
     Still another object of the invention is to provide a blood collection device which is economically manufactured so that it can be used at home with a diagnostic kit, and then thrown away. 
     Still a further object of the invention is to provide a device which reliably collects the desired volume of blood in a sterile chamber in a very simple manner. 
     These and other objects of the invention are accomplished in a housing comprising inner and outer spaced apart pads or walls separated by a compressible, axially extending, pad-bridging enclosure. A double-ended cannula is axially slideably carried by the inner pad and is axially aligned with an evacuated collecting tube closed by a penetrable cap. The system is designed to prevent the double-ended cannula from penetrating the cap of the evacuated collecting tube upon compression of the inner and outer pads of the housing, until after penetration of the epidermis by the cannula. 
     Other objects and advantages of the invention will be pointed out specifically or will become apparent from the following description when it is considered in conjunction with the appended claims and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings FIG. 1 is a sectional side elevational view showing the device in initial position placed in contact with a tip of a finger or the like which is illustrated in chain lines. 
     FIG. 2 is a similar view illustrating the position of the component parts when a compression of the housing has occurred and the lower end of the needle or cannula has penetrated the skin of the finger. 
     FIG. 3 is a further view illustrating the final position of the various components when a full compression of the device has occurred and blood is being drawn into the sample-collecting tube. 
     FIG. 4 is a fragmentary view showing the components in the FIG. 3 position and illustrating an alternative construction. 
     FIG. 5 is a view similar to FIG. 1 wherein another embodiment of the invention is disclosed, wth the components in initial position prior to compression. 
     FIG. 6 is a view similar to FIG. 2 in which a partial relative compression of the upper and lower portions of the housing has occurred; and 
     FIG. 7 is a view similar to FIG. 3 in which a full compression of the housing parts has occurred and blood is being drawn up into the sampling chamber. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now more particularly to the accompanying drawings, and in the first instance to FIGS. 1-3, rectangular or circular upper and lower pads 10 and 11 are shown connected by an enclosing bellows 12 to form a housing generally designated H. The pads or end wall members 10 and 11 are mentioned as upper and lower members only for the sake of convenience since it should be clear that the device will also be operative when turned on its side. The lower pad 11 is provided with a central bore or opening 13 which can be placed adjacent the tip of a finger generally designated F, for instance, when it is desired to draw a blood sample. 
     Fixed to the lower member 11 is a rigid tubular guide 14 having an inner passage 15 which accommodates and slidably guides a double-ended cannula or needle 16 having sharpened puncturing ends 16a and 16b. Mounted above the needle is a collection container 17, which is fixed in a well 10a provided in the top member 10. The outer end of chamber 17 is removably closed by a cap assembly, generally designated C, which includes a puncture sealing rubber stopper member 18 inboard of an outer foil cap backer 19. Cap C snugly closes the open end of the tube 17, which is evacuated at the time cap C is tightly applied. 
     Provided in surrounding relation with the tubular post 14, is a coil spring 20 which exerts a predetermined upward pressure on a stop disk 21 which is fixed to the cannula 16 at a predetermined spaced distance from the lower end of the cannula. The spring 20 normally maintains the cannula 16 in the FIG. 1 position with the lower end 16b of the cannula in axial alignment with the opening 13. The resistance to compression of cannula return spring 20 is such that the lower end of cannula 16 will penetrate the epidermis or skin of the finger F prior to the time the upper end 16a of the cannula 16 penetrates the stopper portion 18. The durometer of stopper 18 is therefore such that its resistance to penetration is greater than the force required to compress spring 20. Thus, both the spring 20 and stopper 18 are carefully engineered so that, when the parts are in the FIG. 2 position, penetration of the skin has occurred prior to the time stopper 18 has been penetrated. With this construction, there is assurance that the vacuum in tube 17 will not be dissipated and will be effective to draw the blood up into the container. The foil 19 is so thin as to offer no appreciable resistance to penetration. 
     THE OPERATION 
     In operation, with the device placed in contact with the tip of the finger F as shown in FIG. 1, the pad 10 is depressed toward the lower pad 11 to compress the housing H. As FIG. 2 indicates, the relative resistance to puncture of the rubber 18 and the skin of finger F, taken with the resistance to compression of spring 20, are such that the cannula 16 first penetrates the skin as indicated in FIG. 2. A further compression of the pad 10 toward the pad 11 is illustrated in FIG. 3 and shows the final position of the parts when a blood sample is being delivered to the interior of container 17. 
     AN ALTERNATIVE PENETRATION CONTROL DEVICE 
     In FIG. 4, a dual-spring device is utilized in which a second stiffer compressible spring 22 surrounds the upper end of the cannula and bears against the upper side of stop 21. Except for this, all of the parts are identical to the components previously described and for purposes of convenience have been identified by the same numerals and will not be redescribed. In this embodiment of the invention, spring 22 acts to increase the resistance to puncture of the cap C, the springs 22 and 16 acting in opposition to one another on opposite sides of the stop 21 to ensure that it is the epidermis of the skin which is punctured prior to puncture of the cap assembly C. 
     ANOTHER EMBODIMENT OF THE INVENTION 
     FIGS. 5-7 illustrate another embodiment of the invention, and in these Figures those components which remain the same have been identified by the same numbers as previously, and the description of these components will not be repeated In this embodiment of the invention, a pair of compressible rigid plastic foams 23 and 24 forming an enclosure for the tube 17 and needle 16 are provided between the pads 10 and 11, and the spring 20 can be eliminated. The upper foam member 23 is recessed as at 23a, 23b, and 23c centrally to receive the container 17 and to provide a passage for cannula 16. The foam layer 24 is recessed as at 24a and 24b to receive the tubular post 14 and the needle stop 21. Foam layer 23 is a more riqid foam than foam 24 and is considerably more resistant to crush than lower foam layer 24. 
     In operation, when the upper pad 10 is moved toward the lower pad 11 to compress the device the greater resistance to crush of layer 23 ensures penetration of the cannula 16 into the skin to the extent shown in FIG. 6 prior to complete penetration of the cap assembly C. With further compression of the layers 23 and 24 to the FIG. 7 position, blood is being drawn by the vacuum in container 17 up into the container 17 in the same manner as previously. The relative crushability of foam layers 23 and 24, taken with the resistance to puncture of the cap assembly C insures the sequential penetration of the two ends of cannula 16. 
     It is to be understood that the embodiments described are exemplary of various forms of the invention only and that the invention is defined in the appended claims which contemplate various modifications within the spirit and scope of the invention.