VELOCITY OF BLOOD FLOW AND STROKE VOLUME OBTAINED FROM THE PRESSURE PULSE *

Abstract

Based on the Navier-Stokes equation, the first time derivative of the aortic pressure,[image]can be related approximately to the instantaneous blood velocity, u, by the equation: [image] asu where t is time, p is the blood density, and a is a "blood friction" constant. This equation can be instantaneously and continuously solved for u, the blood velocity, if the first time derivative of pressure, [image]is known. This can be obtained by differentiation of the pressure pulse. The area under the blood velocity curve so obtained is proportional to stroke output. In eight dogs, the computed stroke volume was compared with the stroke output determined simultaneously with the dye dilution technique. In each dog, multiple points (a total of 66) were obtained with cardiac outputs varying from 500 to 3,000 cc/min. A correlation coefficient of .97 was obtained.