GB1461345A - Method and device for determining the perfusion efficiency factor of animal tissue - Google Patents

Abstract

1461345 Perfusion efficiency factor (blood perfusion and blood concentration) L ESCHWEILER & CO 29 Jan 1974 03974/74 Heading G1N(E) In a device-for measuring the "perfusion efficiency factor" (p.e.f.) of a piece of animal tissue, the perfusion of the indicator is measured with the aid of one or more temperature sensors 11, 13. (The p.e.f. is a function of the rate of flow or perfusion I of an indicator - say blood with a radio-active tracer in it - flowing through the tissue, and a function of the concentration C of the indicator i.e. p.e.f. = F(I,C)). One sensor 11 is attached to a temperature controlled annulus 10 of good thermo-conductive material. In some cases Figs. 1, 2 and 4, Fig. 4 (not shown) a temperature sensor 13 is positioned centrally of the annulus so as to be in contact with the tissue. Thus by measuring the temperature difference between the annulus (which is maintained at a higher temperature than the body temperature of the tissue by a heating coil 12) and the temperature of the tissue at the centre of the annulus, a value of the perfusion of the indicator (blood) can be determined. A value can also be determined by measuring the amount of heat required to maintain the annulus 10 at a predetermined temperature above the body temperature. The indicator concentration can be measured with the aid of a radio-active detector 14, Fig. 1 (when a radio-active tracer is present). Alternatively the indicator cencentration may be measured polarographically, by a network of electrodes 23, 24, 25 and 26 imbedded in glass 22. The electrodes are in contact with an electrolyte which may be stored in a foil 28 surrounded by a gas-permeable membrane 27 to enable measurement of the local oxygen gas pressure given out by the tissue. The electrodes 23, 24 and 25 have small time constants and are located at the corners of an equilateral triangle Fig. 5 (not shown), the other electrode 26 which serves as a calibrating electrode and has a high time is located at the centre of the triangle. The electrical outputs of the two measuring instruments may thus be combined Fig. 6 (not shown) to provide a value of the perfusion efficiency factor. The entire measuring means is accomodated in a housing 15 provided with an annular groove 16 with support rings 17. The groove 16 is connected via a passage 16a with a nipple 18 to a vacuum pump to permit fitment of the measuring means to the tissue. The housing may also be provided with a flange 31 having adhesive members 31. The housing itself may be incorporated in an inflatable pressure exerting cuff D which can be placed around the human arm &c. Upon inflation the pressure exerted will locally interrupt the supply of blood so that the extent of skin breathing can be determined by the time derivative of the oxygen gas pressure.