Closure of digital arteries in high vascular tone states as demonstrated by measurement of systolic blood pressure in the fingers.

Finger systolic blood pressure (FSP) was measured indirectly in normal subjects and patients with primary Raynaud phenomenon by applying a thin-walled plastic cuff around the finger and a strain gauge more distally to detect volume changes. Inducing a high vascular tone in one or more fingers by direct cooling or intra-arterial noradrenaline infusion caused a marked drop in FSP in the exposed fingers, but not in the non-exposed fingers of the same hand. The fact that the non-exposed fingers retained the normal (arm systolic) pressure level is taken to indicate that palmar arch blood pressure also remained normal. In the high vascular tone state, a large transmural pressure difference must apparently be established before the digital arteries are forced open. The lowered opening pressure constitutes a manifestation of the closure phenomenon of the digital arteries described in patients with vasospastic arterial disease. It implies an underestimation of palmar arch systolic pressure measured indirectly on the fingers. FSP measured under these circumstances may be taken as an estimate of the vascular tone, and can be employed in diagnosis and quantification of vasospastic disorders.