The blood flow through the hand during local heating, release of sympathetic vasomotor tone by indirect heating, and a combination of both

The local application of heat to the hand dilates the blood vessels, and hence the blood flow through the hand increases (Hewlett, van Zwaluwenberg & Marshall, 1911). According to Abramson (1944) this procedure can produce maximal dilatation of cutaneous vessels. When the hand is immersed in water at 44-450 C, which is about as hot as can be borne without discomfort, the oxygen and carbon dioxide contents of the venous blood from the hand are similar to those of the arterial blood (Goldschmidt & Light, 1925). When distal parts of the body are heated there is also a large increase in the blood flow through the hand due to the release of sympathetic vasomotor tone (Lewis & Pickering, 1931; Gibbon & Landis, 1932). The object of the present investigation was to determine whether an even greater hand blood flow could be produced by a combination of direct heat with release of sympathetic vasomotor tone by indirect heating than could be obtained by either procedure applied separately. The results have already been reported briefly (Roddie & Shepherd, 1955).