BLOOD-FLOW MEASUREMENTS IN LOWER-LIMB ARTERIES USING DUPLEX ULTRASOUND

The increase in blood flow in exercise is to provide more oxygen to ti ssues. The kinetics of flow at the common femoral artery bifurcation w ere established in normal subjects together with its relationship with oxygen uptake. Furthermore, the changes in flow were evaluated in pat ients undergoing superficial femoral artery angioplasty. After a known anaerobic test (Wingate test), normal subjects underwent a preferenti al increase in profunda femoris artery flow (ninefold increase), compa red with superficial femoral artery flow (fourfold increase), indicati ng predominantly thigh exercise. The relationship between oxygen uptak e and lower limb blood how was studied before, during and after modera te intensity exercise. Oxygen uptake was measured by mass spectrometry and assessed by breath-by-breath analysis. The rate of increase for l imb 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 onse t of exercise. This implies that limb blood flow is in excess of the o xygen requirements of muscle and therefore not the critical determinan t for oxygen uptake by muscle. Flow in the lower limb arteries was mea sured before and after superficial femoral artery angioplasty in 22 pa tients. In addition, collateral blood flow was estimated using a mathe matical model. Followup was carried out to 1 year. At 1 month, a signi ficant 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 i n collateral flow (from 186 +/- 34 to 18 +/- 8 ml min(-1), P < 0.05) w as noted with no change in total limb blood flow. As expected, a signi ficant 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 reli ably be obtained in the lower limb, allowing the kinetics of flow afte r exercise and the changes in flow after surgical intervention to be e valuated. This work provides a foundation for the study of oxygen kine tics and limb blood flow in athletes, the elderly and patients with pe ripheral vascular disease.