ULTRASOUND DOPPLER ESTIMATES OF FEMORAL-ARTERY BLOOD-FLOW DURING DYNAMIC KNEE EXTENSOR EXERCISE IN HUMANS

Ultrasound Doppler has been used to measure arterial inflow to a human limb during intermittent static contractions. The technique, however, has neither been thoroughly validated nor used during dynamic exercis e. In this study, the inherent problems of the technique have been add ressed, and the accuracy was improved by storing the velocity tracings continuously and calculating the flow in relation to the muscle contr action-relaxation phases. The femoral arterial diameter measurements w ere reproducible with a mean coefficient of variation within the subje cts of 1.2 +/- 0.2%. The diameter was the same whether the probe was f ixed or repositioned at rest (10.8 +/- 0.2 mm) or measured during dyna mic exercise. The blood velocity was sampled over the width of the dia meter and the parabolic velocity profile, since sampling in the center resulted in an overestimation by 22.6 +/- 9.1% (P < 0.02). The femora l arterial Doppler blood flow increased linearly (r = 0.997, P < 0.001 ) with increasing load [Doppler blood flow = 0.080.load (W) + 1.446 l/ min] and was correlated positively with simultaneous thermodilution ve nous outflow measurements (r =; 0.996, P < 0.001). The two techniques were linearly related (Doppler = thermodilution.0.985 + 0.071 l/min; r = 0.996, P < 0.001), with a coefficient of variation of similar to 6% for bath methods.