The hydraulic impedance of the lower limb: its relevance to the success of bypass operations for occlusion of the superficial femoral artery.

Simultaneous measurements of pressure and flow waves were made in the course of 25 femoropopliteal bypass operations. From these measurements the the hydraulic impedance of the arterial system in the lower limb was calculated. The values obtained were correlated with the results of the operations. Although reconstruction reduced the impedance we were unable to predict accurately the probable result of the operation on the basis of these measurements. The results suggest that success is more closely related to a good collateral circulation than to "run off".