How to quantify an arterial stenosis: a study on the femoral arteries of dog and man.

The blood supply to the femoral bed was studied in anaesthetised dogs before and after producing arterial stenoses. The blood supply system consisted of the vessels proximal to the site of measurement in the femoral artery and was characterised by a supply graph, which related mean perfusion pressure to mean flow. The different pressures and flows were obtained using an artificial periphery, the impedance of which was changed from beat to beat. The supply graph was approximated by a parabola with two parameters: the intercepts with the pressure and flow axes, the latter indicating the maximum mean flow. For constant aortic pressure the maximum mean flow appeared to be linearly related to the cross sectional area of the stenosed section (r = 0.98). Maximum mean flow was already considerably reduced before the stenosis became critical--that is, before physiological flow was measurably diminished. The change in maximum mean flow was therefore used to quantify the haemodynamic effects of stenoses that were less than critical. Blood supply graphs of the superficial femoral arteries were determined also in seven patients undergoing a femoropopliteal bypass operation. The maximum mean flow correlated well with the degree of obstruction determined from the preoperative angiograms (r = 0.90).