Comparison of computed aortic blood velocity with that of electromagnetic flowmeter

¹ Department of Medicine, Medical College of Alabama; and Medical Service, Veterans Administration Hospital, Birmingham, Alabama

The probe of an electromagnetic flowmeter was placed on the ascending aorta of five dogs. Aortic blood pressure was obtained from the same area. This pressure signal was fed into a simple computer circuit designed to solve a modification of the Navier-Stokes equation. The output of this circuit was assumed to be proportional to blood velocity and was compared directly with the velocity obtained with the electromagnetic flowmeter. The peak amplitudes and the stroke volumes (represented by the area under the velocity tracings), obtained simultaneously by the two different methods, were compared. Each dog was bled, transfused, and given methoxamine and nitroglycerin to produce a wide variation in stroke volume and blood pressure. A correlation coefficient of .93 was obtained from 350 paired stroke-volume values. Thus, it appears that in a wide variety of conditions, stroke volume may be derived from the aortic pressure pulse by the computer technique.