Enhanced interstitial fluid collection

Abstract

A sampling apparatus for interstitial fluid includes a pressure ring surrounding a collection needle. The pressure ring and needle are movable relative to one another for the ring to first engage a patient's skin surface prior to insertion of the needle.

1 . A sampler for collecting interstitial fluid from a skin layer, said sampler comprising: 
 a sampling needle having an axis and a distal end;    a first pressure surface at least partially surrounding said needle in spaced relation thereto;    said needle and said first pressure surface movable relative to one another along a path of travel generally parallel to said axis with said needle and said first pressure surface having an extended position and a retracted position;    said extended position characterized by said distal end of said needle extending beyond said first pressure surface;    said retracted position characterized by said distal end of said needle recessed behind said first pressure surface;    first biasing means for biasing said needle and said first pressure surface to said retracted position.    
     
     
         2 . A sampler according to  claim 1  further comprising a second pressure surface at least partially surrounding said needle and movable therewith, said second pressure surface axially spaced from said distal end of said needle by a distance approximating a desired penetration of said needle into said skin layer.  
     
     
         3 . A sampler according to  claim 2  comprising second biasing means for urging said needle and said second pressure surface in a direction outwardly of said first pressure surface.  
     
     
         4 . A sampler according to  claim 2  wherein said second pressure surface and said first pressure surface define a substantially continuous surface when said second pressure surface and said first pressure surface are in generally planar alignment.  
     
     
         5 . A sampler according to  claim 1  wherein said first biasing means is selected for said first pressure surface to be urged against said skin layer with a force sufficient to define a pressurized zone of interstitial fluid opposing said needle prior to penetration of said needle into said skin layer.  
     
     
         6 . A sampler according to  claim 2  wherein said second pressure surface is concave.  
     
     
         7 . A sampler according to  claim 1  wherein said first pressure surface is a distal end of a ring surrounding said needle in spaced relation thereto.  
     
     
         8 . A sampler according to  claim 7  further comprising a piston surrounding said needle and movable therewith, said piston axially spaced from said distal end of said needle by a distance approximating a desired penetration of said needle into said skin layer.  
     
     
         9 . A sampler according to  claim 8  wherein said piston and said ring are in close sliding tolerance.  
     
     
         10 . A sampler according to  claim 9  comprising second biasing means for urging said needle and said piston in a direction outwardly of said ring.