Duct flow and mitral regurgitation during changes of oxygenation in newborn swine

¹ Green Lane Hospital, Auckland, New Zealand

Mitral regurgitation and blood flow through the ductus arteriosus were quantitated during acute changes in oxygenation in 20 newborn swine studied under open-chest conditions during ventilation with 21, 100, or 10% oxygen. Mitral regurgitation and duct flow were estimated from the abnormally early deflections on dilution curves recorded from the left atrium, when compared with those from the aorta, following injection of indicator into the left ventricle. The induction of acute hypoxia resulted in highly significant increase of shunt through the patent ductus arteriosus (P = 0.001). On reoxygenation this shunt diminished significantly (P = 0.01). These effects were present in animals up to 48 hr of age, although the younger animals sometimes had appreciable duct flow under normal conditions of oxygenation while older animals required longer periods of hypoxia to make duct flow evident. The findings support the evidence of previous studies that oxygenation has a marked effect on the patency of the ductus arteriosus. In the same conditions mitral regurgitation was always insignificant.

Submitted on February 17, 1964