The Influence of Oxygen Tension and Some Drugs on Human Placental Vessels

Abstract

Summary. The response of human placentas to different oxygen tensions was studied in perfusion experiments using fresh human heparinized blood. Two different techniques of perfusion were used: constant pressure and constant output. The placental volume, the blood pressure near the afferent cannula and the flow rate through the placenta were recorded. In other experiments the circular musculature of isolated placental vessels was studied. The alterations of the length of the specimen to different oxygen tensions in the blood were registered. The tonus of the fetal placental vessels was found to be dependent on the oxygen tension of the blood. Vasoconstriction occurred when the tension was increased and vasodilatation when the oxygen tension was decreased. The response of the fetal placental circulation to some drugs was studied by means of the constant pressure perfusion technique. These experiments confirmed the findings of previous investigators. The oxygen consumption of the placenta was measured under constant flow. It was found to be 3.7±0.9 ml O 2 per kg and minute.