Evaluation of sympathetic control of digital blood flow

A noninvasive strain-gauge method of measuring blood flow in the digit was used to assess the influence of the sympathetic system in the digit. The sympathetic system was stimulated by the sudden application of ice to the neck, thus avoiding in the hand local reflexes and responses to cold. Seventeen normal subjects responded in similar fashion. Maximum flow reduction ranged from 26% to 92%, with a mean of 61%. This method should be useful diagnostically and for research when sympathetic reactivity, in contrast to basal sympathetic tone, needs to be determined.