Directional arterial flow velocity: a sensitive index of changes in peripheral vascular resistance.

The effect of peripheral vascular resistance of directional arterial flow velocity was determined utilizing the directional Doppler velocity detector under experimental conditions. Femoral arterial resistance was increased and decreased, and arterial pressure, venous pressure, volume flow, and directional flow velocity were measured in the femoral artery. An increase in peripheral vascular resistance was associated with a marked increase in reverse flow and a decrease in forward flow velocity. Reverse flow decreased and forward flow velocity increased when resistance was lowered. The ratio of peak and mean reverse/forward (r/f) flow velocity changed in a linear relationship with vascular resistance. The increase in resistance associated with progressive hypovolemia was paralleled by an increase in r/f flow velocity which occurred before blood pressure declined. Thus alterations in directional arterial flow velocity can be used as a sensitive indicator of changes in peripheral vascular resistance.