Method and apparatus for determining the perfusion efficiency factor of animal tissue

Abstract

The perfusion rate in animal tissue is measured percutaneously at a specific locus, and at the same time the indicator concentration is percutaneously measured at the same locus so that the perfusion efficiency factor can be determined. Apparatus for carrying out the above method is also disclosed comprising, in combination, a first and a second wall means defining a first and a second surface, each placed in contact with animal tissue to be measured and respectively cooperating with first and second sensor means so that the temperatures of said surfaces can be compared and simultaneously processed with the measurement of the indicator concentration performed by a separate measuring means also in contact with the tissue, so that the perfusion efficiency factor can be determined.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims: 
     
       1. A method of determining the perfusion efficiency factor of animal tissue having blood vessels containing indicator substances therein, comprising the first step of percutaneously measuring the perfusion rate in animal tissue at a specific locus, said first step including heating a first member adapted to be placed against the tissue to be measured, measuring a first temperature of said first member, measuring a second temperature of a second member located centrally of said first member, comparing said first and second temperatures and forming a first differential signal which is proportional to the perfusion rate of the tissue; the second step of simultaneously percutaneously measuring the concentration of the indicator substances in the blood vessels in the tissue at the same locus and generating a second signal which is proportional to the concentration of the indicator substances in the blood vessels; and the third step of processing said first and second signals for generating a third signal which is indicative of the perfusion efficiency factor. 
     
     
       2. A method as defined in claim 1; and further comprising the subsequent steps of locally interrupting the circulation of blood through the tissue; and measuring the skin breathing factor by determining the time derivative of the oxygen pressure resulting from such interruption. 
     
     
       3. In a device for percutaneously measuring the perfusion efficiency factor of animal tissue having blood vessels containing indicator substances therein, a combination comprising a first member defining a first surface adapted to be placed against tissue to be measured; heating means for producing a controlled temperature in said first member at said first surface thereof; first sensor means for measuring a first temperature of said first surface; a second member defining a second surface surrounded by and located substantially centrally of said first surface; second sensor means for measuring a second temperature of the tissue at said second surface; comparator means for comparing said first and second temperatures and forming a first differential temperature signal which is proportional to the rate of perfusion of the tissues; concentration measuring means also surrounded by said first surface and operative for measuring the concentration of said indicator substances in the blood vessels in the tissue and generating a second signal which is proportional to the concentration of the indicator substances in the blood vessels; and combining means for simultaneously processing said first differential temperature signal and said second concentration signal at the same locus and generating a third signal indicative of the perfusion efficiency factor. 
     
     
       4. A combination as defined in claim 3; and further comprising an inflatable pressure-exerting cuff operative for effecting the interruption of blood circulation through the tissue; said members, said heating means, said sensor means, and said concentration measuring means being mounted in said cuff. 
     
     
       5. A combination as defined in claim 3, said concentration measuring means comprising a plurality of platinum electrodes having respective faces, an electrolyte in operative contact with said faces, and a gas-permeable membrane covering all of said faces; and wherein said first surface is annular and said first member means constitutes a counter-electrode for said platinum electrodes. 
     
     
       6. A combination as defined in claim 5, wherein said first member is at least at said first surface composed of Ag/AgCl and has a low thermal capacity; and wherein said heating means comprises electric heating means operative for producing at said first surface a constant temperature of selectable level. 
     
     
       7. A combination as defined in claim 6, wherein said concentration measuring means comprises four of said platinum electrodes, and wherein said platinum electrodes are connected in parallel with one another. 
     
     
       8. A combination as defined in claim 7, wherein three of said platinum electrodes have a small response time, and wherein one of said platinum electrodes has a large response time and serves as a calibrating electrode. 
     
     
       9. A combination as defined in claim 3, said first surface being annular and being formed with an annular groove; and further comprising connecting means for connecting said groove with a vacuum pump. 
     
     
       10. A combination as defined in claim 3; and further comprising adhesive means for removably connecting said device to the tissue being measured, with said first surface being adapted to contact said tissue. 
     
     
       11. A combination as defined in claim 3, wherein said heating means comprises electric heating means operative for producing at said first surface a constant temperature of selectable level. 
     
     
       12. A combination as defined in claim 3, wherein said heating means is regulatable for adjusting the temperature of said first surface to between 37° and 42° C. 
     
     
       13. A combination as defined in claim 3, wherein said tissue has a first temperature, and wherein said heating means is regulatable for adjusting the temperature of at least said first surface to a level higher than said first temperature. .Iadd. 14. A method for determining the perfusion efficiency factor of animal tissue having blood vessels containing indicator substances therein, comprising: the first step of percutaneously measuring the perfusion rate in animal tissue at a specific locus, said first step including heating a member adapted to be placed against the tissue to be measured to heat an area of skin to a constant temperature higher than skin temperature and generating a first signal related to the amount of heat supplied, the amount of heat being proportional to the perfusion rate of the tissue;   the second step of simultaneously percutaneously measuring the concentration of the indicator substances in the blood vessels in the tissue at the same locus and generating a second signal which is proportional to the concentration of the indicator substances in the blood vessels; and   the third step of processing said first and second signals for generating a third signal which is indicative of the perfusion efficiency factor.   
     
     
        .Iaddend..Iadd. 15.  In a device for percutaneously measuring the perfusion efficiency factor of animal tissue having blood vessels containing an indicator substance therein, a combination comprising: a member defining a surface adapted to be placed against tissue to be measured;   heating means for producing a constant temperature in said member at said surface;   means for measuring the heat supplied to keep said temperature constant, the heat being proportional to the rate of perfusion in the tissue, and for generating a signal proportional to said rate of perfusion;   concentration measuring means for measuring the concentration of said indicator substance in the blood vessels in the tissue and generating a second signal which is proportional to the concentration of the indicator substance in the blood vessels; and   combining means for simultaneously processing said first perfusion rate signal and said second concentration signal at the same locus and generating a third signal indicative of the perfusion efficiency factor.   
     
     
        .Iaddend..Iadd. 16.  A combination as defined in claim 15, wherein said concentration measuring means include a plurality of electrodes, an electrolyte in contact with said electrodes, and a gas permeable membrane covering said electrodes, and further wherein said member constitutes a counter-electrode for said electrodes. .Iaddend. .Iadd. 17. A combination as defined in claim 16, wherein said heating means comprises electrical heating means for producing a constant temperature of selectable level at said surface. .Iaddend.