Effect of Arm Position on Circulation Through the Fingers

Abstract

Finger tips of comfortably warm seated subjects were supported at various levels above or below the horizontal plane through the sternal notch. The heat elimination from finger tips to water in the range 29[degree]-32[degree]C was measured calorimetrically. Results were adjusted to allow for the rising temperature of the calorimeter, and fluctuations in general vasomotor activity; there was evidence that the precooling of arterial blood arriving at the fingers was neither large nor variable. The heat elimination from finger tips at all levels from 7.5 to 68 cm below the sternal notch was slightly but significantly greater than at the reference level 4 cm above the sternal notch. The heat elimination from finger tips 11 or 38.5 cm above the sternal notch was markedly less than at the reference level. Responses were similar in subjects in whom peripheral vasomotor tone had been released. The increased heat elimination from the dependent fingers is considered to indicate an unaltered or slightly increased blood flow. In no experiment was there any evidence for a reduction in the blood flow through dependent fingers, but a transient reduction might not have been detected by the method used.