REPRODUCIBILITY OF THE VASCULAR-RESPONSE TO HEATING IN HUMAN SKIN

Blood flow in human skin increases enormously in response to direct he ating. If local skin temperature is held above 42 degrees C, blood flo w eventually stabilizes at a level beyond which other influences, barr ing change in blood pressure, can produce no further increase. If this maximal level is a reproducible characteristic of an individual's cut aneous vasculature, it could be useful in comparing individuals; for e xample, in their response to hyperthermia. Our experiments were carrie d out to discover whether the maximal response of the vasculature of t he skin of the forearm can be reproduced within reasonable limits and, also, to clarify the time course of the response. We used water spray ed over the surface of the forearms of 10 subjects to hold skin temper ature above 42 degrees C for 60 min. During the last 10 min of heating , forearm blood flow (via venous occlusion plethysmography) was stable , at a level ranging from 16 to 38 ml.min(-1).100 ml(-1). This level, normalized to a blood pressure of 100 mmHg, was reproduced in a given individual on four or five occasions, with an average coefficient of v ariation of 10%. The response was 77 +/- 11% (SD) complete after 20 mi n of heating. Elapsed time at 90% of the final value was 35 +/- 9 (SD) min. We conclude that the maximal forearm blood flow response to loca l heating is a reproducible characteristic of the cutaneous vasculatur e with potential utility in the scaling of responses between and withi n individuals.