The instantaneous pulsatile flow-pressure relationships across the ductus arteriosus were studied in fetal lambs before and after progressive lung expansion. Analysis of the same flow-pressure relationship was simulated on an analog computer using a mathematical model of the fetal circulation. The results demonstrate that 1) the blood flow through the ductus has a distinctive inertial characteristic and 2) there exists an asynchrony between the ejection of the two ventricles; the ejection of the right ventricle precedes that of the left. Both these factors explain the paradox of flow across the ductus from pulmonary artery to aorta (right-to-left shunt) which is seen when the lungs are incompletely expanded and the aortic pressure is higher than the pulmonary artery pressure.
- fetal vascular dynamics
- ductus circulation
- fetal analog computer simulations
- Copyright © 1965 by American Physiological Society