THE ROLE OF LUNG PERFUSATE PO2 IN THE CONTROL OF THE PULMONARY VASCULAR-RESISTANCE OF EXTERIORIZED FETAL LAMBS

The isolated perfused lower left lung lobe of the exteriorized fetal lamb was used to define quantitatively the relationship between pulmonary perfusate oxygen tension and pulmonary vascular resistance (PVR) in the fetus at multiple tensions over the range 8.3 to 433 mm Hg. This allowed variation of the perfusate PO over the range of partial pressures from less than 10 mm Hg to cover 400 mm Hg while constant values of PCO, temperature and perfusate flow were maintained. In all animals, calculated pulmonary vascular resistance varied in an inverse manner with the perfusate PO. The relationship between PVR and perfusate oxygen tension is described by the equation: PVR = 7.67 - 1.54 (log PO2) R2 = 0.70. While others have shown that a single, large increase in blood oxygen tension will decrease the PVR in fetal lambs, these data present the first quantitative description of the role of oxygen tension in the modulation of fetal pulmonary vascular resistance as determined at multiple perfusate oxygen tensions over a fifty-fold range. © 1990.