Altered sensitivity of digital blood flow to acute vibration in patients with vasospastic disease

Fifteen patients with primary Raynaud's, 18 patients with vibration induced white finger (VWF) and 15 controls were exposed to sine wave vibration, with an amplitude of 0.15 mm and frequencies of 40, 80 and 120 Hz. Baseline digital blood flow was measured using venous occlusion strain gauge plethysmography. A digit was vibrated for 1 min and subsequent blood flow measurements were taken from both vibrated and non-vibrated digits. Vibration at 40 Hz causes a significant decrease in flow in the vibrated digits of the control group only (P less than 0.05, Wilcoxon test). Vibration at 80 Hz shows a significant decrease in blood flow in the vibrated digits of both the control and the VWF groups (P less than 0.005) and also in the non-vibrated digits of the VWF group (P less than 0.05). Vibration at 120 Hz significantly decreases blood flow in the vibrated digits of normal control, VWF and Raynauds group (P less than 0.001). The Raynaud's non-vibrated digits also had decreased flow (P less than 0.005). These results imply that patients with established vasospastic disease are less sensitive to the direct effects of acute vibration than controls. The results also imply that vibration at 40, 80 and 120Hz affect digital blood flow in controls through local mechanism. Vibration at certain frequencies, appears to modulate blood flow in patients with vasospastic disease by acting through central mechanisms.