Heat-induced vasoconstriction in the fingers: a mechanism for reducing heat gain through the hand heated locally

Abstract

This study examined the effect of local heating on the blood flow of the finger or forearm in male subjects in an environment of 35 degrees C--40% (r.h.). One hand or forearm was immersed in a water bath the temperature of which (Tw) was raised by 1 degrees C every 10th min from 35 degrees to 43 degrees C, while the other hand or forearm was kept at a constant Tw of 35 degrees C. Blood-flow (BF) was measured by venous occlusion plethysmography, using temperature-compensated mercury-in-Silastic strain gauges. Finger BF in the heated hand was significantly lower than that in the control hand at TwS of 37 degrees -41 degrees C, mostly for the first few minutes of each heating period. Thereafter, finger BF in the heated hand gradually returned toward the previous values. At TwS of 39 degrees -40 degrees C, however, finger BF in the heated hand remained lower than the control values for the entire period of heating. At TwS of 42 degrees -43 degrees C, finger BF in the heated hand greatly increased after an initial transitory fall. In the forearm skin, however, no such vasoconstriction in response to local heating was observed. All this suggests that a rise in skin temperature to above the core temperature produces paradoxical vasoconstriction in the finger, which may be a mechanism to reduce heat gain through the hand heated locally at higher temperatures.

Free flow of sweat due to loss of surface tension at sweat droplets causes water-induced skin wrinkling

“…In the case of warm water, excessive cooling in the form of increased sweating causes the vasoconstriction. If the heat gain to the fingers is more than the heat loss through sweating, then blood flow will increase to the fingers as observed with higher temperatures (17). Increased blood flow further increases the loss of sweat.…”

“…Warm water also exerts less pressure on sweat flow than cold water, enabling faster depletion of water from the body. It has been suggested that vasoconstriction in fingers immersed in water in which the temperature was gradually increased is a mechanism to reduce heat gain from the environment (17). An increase in blood flow when the hand was heated using hot air was reported as an objection to the 'heat gain' and vasoconstriction theory (1).…”

Free Flow of Sweat due to Loss of Surface Tension at Sweat Droplet Causes Water-Induced Skin Wrinkling

“…In the case of warm water, excessive cooling in the form of increased sweating caused the vasoconstriction. If the heat gain to the fingers is more than the heat loss through sweating then blood flow will increase to the fingers as observed with higher temperatures [17]. In other case with hot air, blood flow increased due to lack of sufficient cooling mechanism at the hand.…”

“…Warm water also exerts less pressure on the sweat than cold water, enabling faster depletion of water from the body. Nagasaka et al [17] suggested the vasoconstriction in fingers, when immersed in water of which the temperature was gradually increased, as a mechanism to reduce the heat gain from environment. Wilder-Smith and Chow [1] argued that the increase in blood flow when the hand was heated using hot air as an objection to the 'heat gain' and vasoconstriction theory.…”

Skin Vasoconstriction Induced by Local Skin Heating

“…Therefore, separate descriptions of blood flow response may be needed for these two skin areas. a) Finger vasoconstriction evoked by hand heating NAGASAKA et al [23,24,26,27] have recently observed that finger vessels constrict when the hand is heated locally to temperatures above body core temperature. In their study, finger blood flows were simultaneously measured in both hands immersed in separate baths of water whose temperature (TW) was kept initially at 35°C.…”