197
J. Phy8iol. (1975), 249, pp. 197-210 With 8 text-ftgure8 Printed in Great Britain
TEMPERATURE DEPENDENCE OF THE CIRCULATION PATTERN IN THE UPPER EXTREMITIES
BY E. R. RAMAN AND V. J. VANHUYSE From the Fy8isch Laboratorium, Rijkiuniversitair Centrum, Antwerpen, Belgil
(Received 9 July 1974) SUMMARY
1. The rate of blood flow D through the hand and the rate of heat H transferred by that blood flow into the hand were measured on eleven subjects between 18 and 22 years old. The hand was immersed in water, at temperatures ranging from 10 to 400 C. 2. The rate of blood flow was measured with a water-air displacement plethysmograph, which was adapted also to give heat loss measurements. 3. Comparison of the relative values of D and H at different temperatures gives information about the change in distribution of blood flow with temperature. On decreasing water temperature, the change in distribution starts at about 250 C and continues gradually to about 15° C, suggesting that more and more blood is shunted to deep veins. For one of the subjects, no change in distribution pattern was found. INTRODUCTION
The extremities play an important role in the heat conservation and dissipation of the body as they extend into the environment and possess a large relative skin surface (Abramson, 1967; Brengelmann & Brown, 1965). The blood flow in extremities at rest is only partly to satisfy the oxygen requirements of tissues; the greatest role is in thermoregulation. It is generally known that changes in environmental temperature are associated with alterations in the quantity of blood brought to the skin areas of the extremities. Under physiological conditions the heat loss of extremities is accomplished mainly byvasodilation or vasoconstriction of the cutaneous blood vessels. In cold environments heat loss from the extremities can be further reduced by changing the circulation pattern and possibly by counter-current exchange of heat between arteries and veins in the limbs. Little has been added to our understanding of this counter-current system since Bazett, Love, Newton, Eisenberg, Day & Forster (1948) measured with a thermocouple the temperature of blood inside the radial
E. R. RAMAN AND V. J. VANHUYSE artery at the wrist. Counter-current exchange is effective only when the returning blood flows in deep veins alongside the artery rather than in superficial veins. According to Mitchell & Myers (1968), there should be no significant counter-current effect in the arm of man. Their results were obtained from an analytical model. They admit, however, that the available data were insufficient for an adequate comparison with the developed theory. Furthermore, there was no possibility of any change of the circulation pattern in the accepted model. The purpose of this work was to find information about the change in this circulation pattern in extremities of man as a function of the environmental temperature. As the extent of the rate of heat loss and the countercurrent exchange of heat depends on the relative distribution of the venous blood flow to deep and superficial vessels respectively, one can expect to find that information from measurements at different environmental temperatures of both the rate of blood flow and the rate of heat loss. 198
J. Phy8iol. (1975), 249, pp. 197-210 With 8 text-ftgure8 Printed in Great Britain
TEMPERATURE DEPENDENCE OF THE CIRCULATION PATTERN IN THE UPPER EXTREMITIES
BY E. R. RAMAN AND V. J. VANHUYSE From the Fy8isch Laboratorium, Rijkiuniversitair Centrum, Antwerpen, Belgil
(Received 9 July 1974) SUMMARY
1. The rate of blood flow D through the hand and the rate of heat H transferred by that blood flow into the hand were measured on eleven subjects between 18 and 22 years old. The hand was immersed in water, at temperatures ranging from 10 to 400 C. 2. The rate of blood flow was measured with a water-air displacement plethysmograph, which was adapted also to give heat loss measurements. 3. Comparison of the relative values of D and H at different temperatures gives information about the change in distribution of blood flow with temperature. On decreasing water temperature, the change in distribution starts at about 250 C and continues gradually to about 15° C, suggesting that more and more blood is shunted to deep veins. For one of the subjects, no change in distribution pattern was found. INTRODUCTION
The extremities play an important role in the heat conservation and dissipation of the body as they extend into the environment and possess a large relative skin surface (Abramson, 1967; Brengelmann & Brown, 1965). The blood flow in extremities at rest is only partly to satisfy the oxygen requirements of tissues; the greatest role is in thermoregulation. It is generally known that changes in environmental temperature are associated with alterations in the quantity of blood brought to the skin areas of the extremities. Under physiological conditions the heat loss of extremities is accomplished mainly byvasodilation or vasoconstriction of the cutaneous blood vessels. In cold environments heat loss from the extremities can be further reduced by changing the circulation pattern and possibly by counter-current exchange of heat between arteries and veins in the limbs. Little has been added to our understanding of this counter-current system since Bazett, Love, Newton, Eisenberg, Day & Forster (1948) measured with a thermocouple the temperature of blood inside the radial
E. R. RAMAN AND V. J. VANHUYSE artery at the wrist. Counter-current exchange is effective only when the returning blood flows in deep veins alongside the artery rather than in superficial veins. According to Mitchell & Myers (1968), there should be no significant counter-current effect in the arm of man. Their results were obtained from an analytical model. They admit, however, that the available data were insufficient for an adequate comparison with the developed theory. Furthermore, there was no possibility of any change of the circulation pattern in the accepted model. The purpose of this work was to find information about the change in this circulation pattern in extremities of man as a function of the environmental temperature. As the extent of the rate of heat loss and the countercurrent exchange of heat depends on the relative distribution of the venous blood flow to deep and superficial vessels respectively, one can expect to find that information from measurements at different environmental temperatures of both the rate of blood flow and the rate of heat loss. 198
