METHOD FOR DETERMINING STATUS OF BIOLOGICAL TISSUE AND PHOTOPLETHYSMOGRAPH FOR CARRYING OUT SAME Russian patent published in 1995 - IPC

FIELD: medicine. SUBSTANCE: this method prescribes synchronously measuring constant A^c and variable A^v using photoplethysmographs in following three points, that is, point under study, intact which is symmetrical about latter and reference one, determining relationship between variable A^v and constant A^c of signal component A for each point, calculating rated indices for point under study and intact point which is symmetrical about latter using following equation: K_n= A_n-A_p/A_n+A_p,, where A_n is relative optical characteristic of point n, n denotes ordinal number of certain point, n = 1, 3, 5 ... for points disposed respectively in center of biological tissue zone under study at boundary of biological point zone under study 1 to 2 cm off boundary of zone under study and n + 1 = 2, 4 and 6 for symmetrical points of intact anatomo-topographic zone under study and A_p represents relative optical characteristic of reference point, determining rated indices of symmetry using equation C_n= K_n/K_n+1., and diagnosing pathological changes in given point at C_n< 0,89 < 0.89. For carrying out this method, use should be made of photoplethysmograph including three similar channels A, B and C each of which has irradiation unit incorporating successively connected pulse generator 1, amplitude modulator 2 and radiator 3 proper. Luminous pulses emitted by irradiation unit pass through tissues of biological test subject located between radiator and photo detector or are reflected from latter, modulated in amplitude, and then received by photo detector 4 to whose output are consecutively connected preamplifier 5, rectifier 6, low-frequency filter 7, band-pass amplifier 8, differentiating amplifier 9, comparator 10, and pulse shaper 11 which generate signal of first derivative and discriminate time marks of fixing instances of transition through zero. Automatic intensity control unit incorporating successively connected ripple filter 12, threshold comparison element 13 and adjustment element 14 is connected to output of low-frequency filter 7 to eliminate influence of individual optical characteristics of biological test subject. Outputs of differentiating amplifier 9, band-pass amplifier 8, pulse shaper 11 and adjustment element 14 to respective inputs of recorder 15. EFFECT: higher accuracy of investigation and elimination of factors arising from specific traits of individual organism under examination. 2 cl, 4 dwg