The blood flow in skin and muscle of the human forearm

The venous occlusion plethysmograph measures the total blood flow through all component tissues of a limb segment. It does not give any indication of the relative flow through the skin, muscle and supporting tissues. In the past, observed changes in forearm blood flow have been ascribed, by different workers, to changes in the different component tissues of the limb segment. However, no direct quantitative measurements of the flow in these different tissues have been made in man. Estimates of skin blood flow have been made by Hertzman (1948), using the photo-electric plethysmograph. Behnke & Wilimon (1941) have used the rate of absorption of helium through the skin as an indication of cutaneous blood flow. Hardy & Soderstrom (1938) have, by a study of the skin and deep temperatures, attempted to assess the skin blood flow. The heat elimination of the skin has been measured by Hensel (1952) using a modification of Aschoff's (1944) continuous-flow calorimeter. All these methods can be considered to give an indication of changes in the skin blood flow, but none of them has been correlated with a method which gives a quantitative record of the cutaneous blood flow. The method of physiological skinning of the forearm by iontophoresis with adrenaline developed by Barcroft, Bonnar, Edholm & Effron (1943) has been used to measure skin flow. The forearm blood flow may vary considerably from day to day, even with the subject at rest. Making use of these fluctuations in forearm blood flow, induced by internal and environmental factors, it is possible to estimate the skin and muscle blood flows occurring in the forearm over a substantial range of flows in that segment, and the results are presented in this paper (Cooper, Edholm & Mottram, 1954).