Effect of foot compression on the velocity and volume of blood flow in the deep veins.

The A-V Impulse System reduces the incidence of deep vein thrombosis by pneumatically compressing the venae comitantes of the lateral plantar artery, causing an increase in the velocity of blood in the proximal axial veins. Using a duplex scanner the effects of altering the pressure, pulse duration and frequency of foot compression on the velocity and volume of blood flow in the superficial femoral and popliteal veins were quantified. In 20 legs, foot compression of 50, 125 and 200 mmHg significantly increased the maximum venous blood flow by 9.0, 13.4 and 15.1 ml/s respectively (P < 0.001). Conversely, reducing the frequency of compression from 6 to 3 cycles per min significantly increased the rise in peak flow from 10.1 to 14.8 ml/s (P < 0.001). Changing the duration of compression from 1 to 3 s had no significant effect on peak flow. Increased blood flow is best achieved with high-pressure low-frequency foot compression. Increasing the duration of compression beyond 1 s has no effect on augmentation of flow in the deep veins.