THE ESTIMATION OF THE CUTANEOUS BLOOD FLOW WITH THE PHOTOELECTRIC PLETHYSMOGRAPH

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Abstract
The quantitative correlation between cutaneous blood flow and the amplitude of the photoelectrically recorded cutaneous vol. pulses (Biol. Abstr. 12: 16187. 1938; 15: 10525. 1941) is demonstrated in 2 types of calibration expts. on the finger: 1) the simultaneous measurement of flow and of pulses in the finger pad; 2) the simultaneous measurement of the mean blood flow in the terminal phalanx and estimation of the mean cutaneous vol. pulse of the terminal phalanx by the photoelectric exploration of its surface. Both expts. yield the same value for the flow equivalent of the vol. pulse; the flow equivalent is equal to 0.10 ml./cm.2 skin/ min./"filter unit"; the "filter unit" in turn is a measure of the amplitude of the photoelectrically recorded cutaneous vol. pulse. The flow equivalent may be applied to photoelectric records of vol. pulses in the various skin regions of the body in order to convert these records to estimates of skin blood flow. Topographic inequalities in rates of blood flow are demonstrated to exist over the surface of the finger by both the flow and pulse data.