Effect of hand position on digit and ulnar artery vasoconstrictor reflexes.

The degree of digit and ulnar reflex vasoconstriction is a useful measure of hand sympathetic function. Reflex vasoconstriction is generally expressed as the percentage of reflex reduction in blood flow compared to resting flow. Sympathetic traffic to and from the hand can be altered by environmental testing factors, and lead to a reduction in reflex vasoconstriction. In this study we tested the effect of pronation and supination on inspiratory gasp induced digit skin and ulnar artery vasoconstrictor reflex responses. In 11 healthy subjects (range 21-65 yrs, mean 39 yrs, 8 females, 3 males) the mean second digit vasoconstriction in supination was 55 (SD 19)/44 (SD 20), for pronation 55 (SD19)/48 (SD19); for the fourth digit, in supination 63 (SD18)/59 (SD 21), in pronation 64 (SD15)/69 (SD13) (right and left). Mean ulnar vasoconstriction in supination was 81 (SD 11)/88 (SD11), for pronation 81 (SD10)/86 (SD12) (right and left). For all vascular regions, reflex vasoconstriction was not significantly different between pronation and supination. All subjects felt the pronation position more comfortable and an added benefit of this position was significantly shorter testing time.