Vascular reactivity of cutaneous circulation to brief compressive stimuli, in the human forearm.

Abstract

A brief compressive stimulus is known to induce a rapid hyperemia in skeletal muscles, considered to contribute to the initial phase of functional hyperemia. Whether the same mechano-sensitivity characterizes the cutaneous circulation is debated. This study aims to investigate whether a rapid hyperemic response to compressive stimuli is also expressed by skin blood flow in humans. In 12 subjects, brief compressive stimuli were delivered to the forearm at varying pressures/durations (50/2, 100/2, 200/2, 200/1, 200/5mmHg/s); the sequence was randomized and repeated with the arm above and below heart level. Laser Doppler flowmetry technique was used to monitor skin blood flow. The response was described in terms of peak skin blood flow normalized to baseline (nSBFpeak), time-to-peak from the release of compression, and excess blood volume (EBV, expressed in terms of seconds of basal flow, s-bf) received during the response. The results consistently evidenced the occurrence of a compression-induced hyperemic response, with nSBFpeak = 2.9 ± 1.1, EBV = 17.0 ± 6.6s-bf, time-to-peak = 7.0 ± 0.7s (200mmHg, 2s, below heart level). Both nSBFpeak and EBV were significantly reduced (by about 50%) above compared to below heart level (p < 0.01). In addition, EBV slightly increased with increasing pressure (p < 0.05) and duration (p < 0.01) of the stimulus. For the first time, the rapid dilatator response to compressive stimuli was demonstrated in human cutaneous circulation. The functional meaning of this response remains to be elucidated.