The aortic flow pulse as related to differential pressure. Circulation Research 4

The flow pulsations in the dog's descending aorta were recorded with a noncannulating square-wave electromagnetic flowmeter and found to be at considerable variance with previously pub-lished curves. The validity of the square-wave electromagnetic flows was established by tests of the instrument's adequacy and by comparison with the simultaneously recorded differential pressures. In the genesis of the aortic flow pulse, inertia is dominant and resistance secondary, so that flow is related to the differential pressure pulse mainly through acceleration. E'TLE is known concerning the pulsatilemovement of the blood along the aorta,chiefly because of inadequacies and difficulties in applying existing pulsatile flow-meters. Most of our knowledge has been deduced from pressure pulses recorded at various points along the aorta or by use of dif-ferential pressure flowmeters. Aortic flow pulses obtained by various types of differential pressure flowmeters have been published by Frank,1 Broemser,2 and Green.1 Machella4 published a curve of the time-velocity sequence of the aortic blood flow de-rived from application of the hot wire principle, wherein a heated wire was passed across the lumen of the ascending aorta. This instrument suffers from an inadequate frequency response and failure to differentiate between forward and backward flow. X-ray cinematography was used to study the movement of the aortic blood by Timni6 who followed the moment-to-moment position of radiopaque oil droplets along this structure. McDonald,9 using reflected light, photographed the passage of air bubbles along the rabbit's aorta to derive a velocity curve. The electromagnetic induction principle ha