[Study of the plethysmographic amplification factor during vasodilator treatment. Healthy subject versus primary Raynaud phenomenon].

Digital arterial circulation before and after administration of a vasodilator orally was explored by mercury gauge pulsed plethysmography and photoplethysmography in 12 patients with primary Raynaud's phenomenon and results compared with those of 10 healthy volunteers. The amplification factor F, ratio of amplitude in reactive hyperemia over amplitude at rest was determined in the index before and after 8 mg daily of dihydroergokryptine over 4 weeks. Before treatment, for each of the two plethysmographic technics, a significant increase in mean factor F values was noted in the patients with Raynaud's phenomenon when compared with healthy controls. This is due to a decline in digital arterial flow at rest. Using the mercury gauge plethysmograph, a significant reduction in factor F was observed after vasodilator treatment corresponding to an increase in digital flow at rest without increase in flow during hyperemia. Using photoplethysmography, no significant variation in factor F was noted after treatment. Mercury gauge plethysmography, which measures global digital blood flow appears to be a more sensitive method than photoplethysmography, which measures dermal and hypodermal blood flow, for follow-up of effects of vasodilator treatment on Raynaud's phenomenon.