FLOW-MEDIATED VASODILATION OF A CONDUIT ARTERY IN RELATION TO DOWNSTREAM PERIPHERAL TISSUE BLOOD-FLOW DURING REACTIVE HYPEREMIA IN HUMANS

Arterial conduit vessels dilate in response to increased blood flow st imuli, Our objective was to determine precisely how a change in large arterial diameter results in a change in peripheral tissue blood flow. Using high-resolution ultrasound Doppler echography, we measured the diameter of the right femoral artery at rest, during reactive hyperemi a? and after administration of 2.5 mg of sublingual isosorbide dinitra te In 10 healthy young men, Reactive hyperemia was induced by distal c irculatory arrest followed by reperfusion of the leg ipsilateral (righ t) or contralateral (left) to the side of arterial diameter measuremen ts. Femoral arterial blood flow was calculated by simultaneous measure ment of femoral arterial diameter and blood velocity. The change in sk in blood flow was also analyzed simultaneously by laser Doppler flowme try. Reactive hyperemia induced a 2-fold increase in femoral arterial blood velocity 30 sec after cuff release. During this flow augmentatio n, the femoral artery dilated. The peak of skin blood flow was coincid ent with the peak of femoral arterial vasodilation. The time required for the return of arterial diameter to baseline was longer than that f or blood flow in both the conduit artery and the peripheral skin tissu e. Equivalent cui: occlusion and release of the contralateral limb had no effect on ipsilateral arterial diameter, Isosorbide dinitrate indu ced dilation in all subjects, despite the absence of a significant inc rease in blood velocity. These results indicate that;he human femoral artery dilates in response to increased blood velocity, and that the f low-mediated vasodilation of a large conduit artery is involved in the adjustments of blood flow in the downstream peripheral tissue.