THE DIFFUSIBILITY OF OXYGEN ACROSS THE SHEEP PLACENTA

Abstract

Estimates have been made of: (1) the oxygen tension in blood samples drawn from unanesthetized ewes and their fetuses via chronic catheters in the uterine vein, umbilical artery and umbilical vein between 90 days and full term; (2) the rate of oxygen uptake by the umbilical circulation between 80 and 134 days in a series of anesthetized ewes, and (3) the ‘diffusing capacity’ of the placenta for oxygen in eleven anesthetized ewes in stages of gestation from 81 to 134 days. The results demonstrate: (1) there is no regular change with advancing gestation in the oxygen tension of the blood in the vessels sampled, and (2) the quantity of oxygen taken up by the umbilical blood and the ‘diffusing eapacity’ of the placenta for oxygen both increase as the fetal weight. © 1965 The Physiological Society