The measurement of flow-mediated dilation (FMD) is a standard method to assess endothelial function in the arteries (1,2). In practice, FMD measures arterial dilation after abruptly releasing the flow in previously clamped arteries (1,2). This clamping-releasing process might be considered as an experimental mimic of pulsation and, thereby, an FMD-equivalent measure might be determined by simply recording dilation that is induced by the initiation of flow during the rise of a pulse.

By using piezoelectric and photo-plethysmographic sensors, pressure (PP) and volume pulse (VP) waves were simultaneously recorded from adjacent digits, then their kinetics were compared. The systolic peak in the VP appeared with considerably slower kinetics as compared to that in the PP. The difference in the kinetics—either max. rate of rise or delay time (Fig. 1) computed after length-normalizing the pulses—was found to relate to the (a) subjects’ age, (b) systolic blood pressure and (c) pulse wave velocity. Importantly, the kinetic differences between the PP and the VP of older subjects were apparently eliminated by the administration of sublingual nitroglycerin, suggesting that the rate of rise in the VP is a measure of endothelium-dependent vasodilation.

Our results imply the existence of a nitric oxide-dependent, flow-mediated mechanism of arterial dilation that operates pulse-by-pulse, on which basis a simple pulse contour analysis method, which might provide equivalent results as FMD, is developed to that assess endothelial function in the arteries.