Effect of local warming on hand and finger artery blood velocities.

The effect of local heating on blood velocities in arteries supplying the skin of hand and fingers was studied in subjects kept in their thermoneutral zone. The temperature of one hand was steadily raised from 35 to 43 degrees C in 15 min, whereas the control hand was kept in the air or immersed in a water bath at 35 degrees C. Simultaneous blood velocity recordings from the two hands were made continuously using ultrasound Doppler. In the heated hand, a general rise in blood velocity level was seen. However, the spontaneous fluctuations in blood velocity assumed to be caused by synchronous vasomotor activity of the arteriovenous anastomoses (AVAs) remained unchanged and closely correlated with those in the control hand throughout the experiment. Thus the central nervous control of AVA vasomotion seems to be unaffected by local heating. The elevation of blood velocity in the heated hand is probably due to dilatation of other parts of the vascular bed, e.g., ordinary arterioles in the skin. Earlier investigators, using venous occlusion plethysmography, have reported vasoconstriction in the locally heated human finger. No sign of such heat-induced vasoconstriction was found in this study.