Pulsatile and Steady Pressure-Flow Relations in the Vascular Bed of the Hind Leg of the Dog

Abstract

Instantaneous pressure and flow in the femoral artery of the dog were recorded under steady and pulsatile pressure conditions. Static pressure-flow diagrams and dynamic pressure-flow diagrams over the pulse pressure range at different points in the cardiac cycle were constructed. A comparison was made of the flow corresponding to a) normal pulsatile conditions, and b) static pressures equal to the mean of the pulsatile pressures. The static pressure-flow diagrams were consistent with those described by other workers, and were essentially linear in the ranges studied. Changing from steady to pulsating pressures altered the flow from 40.4 ml/min. to 40.9 ml/min. This difference was less than the measurement accuracy of the flow, although statistical analysis indicated significance to 1%. The dynamic pressure-flow diagram appeared as a ‘loop,’ the shape of which indicated that in 12 of 13 animals, the system was mass controlled and the heart rate was higher than the resonant frequency. In the one exception, the phase angle was negligible and the system was apparently in resonance.