Forearm arterial compliance: a new measure of arterial compliance?

This study has investigated the origin of the pulsatile expansion of the forearm recorded by the amplification of the pulsatile signal derived from a mercury in rubber plethysmograph. Venous occlusion to pressures of 40 mmHg had no effect on the amplitude of the volume pulse, suggesting that the volume pulse originates in vessels distended by pressures above this level. Nitroglycerin in small doses (0.15 mg sublingual) increased the amplitude of the volume pulse without changing forearm vascular resistance, consistent with an arterial origin of the forearm volume pulse. The instantaneous relationship between the volume pulse and arterial pressure (forearm compliance) showed that nitroglycerin increased the volume pulse in association with a reduction in pulse pressure. As the volume pulse probably originates in the arterial system, the increase in forearm compliance is a measure of the increase in arterial compliance induced by nitroglycerin. Both the volume pulse and forearm compliance may be useful indicators of the effect of physiological and pharmacological interventions on the distensile properties of arteries.