Blood flow measurements in lower limb arteries using duplex ultrasound

The increase in blood flow in exercise is to provide more oxygen to tissues. The kinetics of flow at the common femoral artery bifurcation were established in normal subjects together with its relationship with oxygen uptake. Furthermore, the changes in flow were evaluated in patients undergoing superficial femoral artery angioplasty. After a known anaerobic test (Wingate test), normal subjects underwent a preferential increase in profunda femoris artery flow (ninefold increase), compared with superficial femoral artery flow (fourfold increase), indicating predominantly thigh exercise. The relationship between oxygen uptake and lower limb blood flow was studied before, during and after moderate intensity exercise. Oxygen uptake was measured by mass spectrometry and assessed by breath-by-breath analysis. The rate of increase for limb blood flow, as indicated by the time constant, was faster (28.8 +/- 4.4 s; mean +/- sem) than oxygen uptake (41.5 +/- 7.2 s) at the onset of exercise. This implies that limb blood flow is in excess of the oxygen requirements of muscle and therefore not the critical determinant for oxygen uptake by muscle. Flow in the lower limb arteries was measured before and after superficial femoral artery angioplasty in 22 patients. In addition, collateral blood flow was estimated using a mathematical model. Follow-up was carried out to 1 year. At 1 month, a significant decrease in profunda femoris artery flow (from 224 +/- 84 to 98 +/- 43 ml min-1, P < 0.05, paired t test) and a marked diminution in collateral flow (from 186 +/- 34 to 18 +/- 8 ml min-1, P < 0.05) was noted with no change in total limb blood flow. As expected, a significant increase in superficial femoral artery blood flow was seen (148 +/- 79 to 312 +/- 94 ml min-1, P < 0.05). From the studies, it can be seen that non-invasive duplex ultrasound flow measurements can reliably be obtained in the lower limb, allowing the kinetics of flow after exercise and the changes in flow after surgical intervention to be evaluated. This work provides a foundation for the study of oxygen kinetics and limb blood flow in athletes, the elderly and patients with peripheral vascular disease.