Analytical model for the temperature dependence of the circulation pattern in upper extremities.

An analytical model for the circulation in the upper extremities of man is studied under the condition that the hand is immersed in water at different temperatures. The arterial and venous system is represented by one artery and two veins. One of the veins lies close to the deep lying artery; the other one is a cutaneous vein. The model permits a qualitative description of the dependence on temperature of the rate of heat loss of the hand as a function of the rate of blood flow and the water temperature, by means of parameters which determine the behaviour of the considered system. One parameter accounts for the relative amount of the rate of blood flow along deep and cutaneous veins. Comparison with experiment leeds to the following results. At water temperatures 0Hw higher than 25 degrees C about 10% of the blood is returning through the deep vein; for water temperatures lower than 13 degrees C this percentage becomes about 80%. In between the circulation pattern changes gradually. The influence of the counter-current effect, between the artery and the deep vein, on the heat loss of the hand is studied. The arterial blood temperature at the entrance in the hand is compared with the available experimental results.