Title: 3 Hypoxemia and Protein Clearance from the Pulmonary Vascular Bed of Pups
Abstract: Clearances of plasma proteins from, the pulmonary circulation (Cl prot.) are 2–3 fold greater for 2–3 weekold pups than for adult dogs (J. Pediat. 69: 966, 1966). Those data probably indicate greater permeability of the pulmonary capillaries to plasma proteins (PCP) for pups than for adult dogs as transpulmonary artery wedge pressure and effective pulmonary blood flow were similar for pups and adult dogs. The effect of hypoxemia on Cl prot. has now been evaluated in five anesthetized, normothermic, artificially ventilated 2–3 week-old pups. Cl prot. was calculated from lung lymph and serum protein concentrations and lung lymph flow rate and expressed as μ1 plasma cleared/100 g lung/h. During 30 min ventilation with 10 % O2, mean PO2 dropped from 102 to 35 mm Hg, and mean Cl prot. increased 38 % (range 15 to 49 %) over control values. Cl prot. returned to control values on return to 21 % O2 ventilation in 3 pups, and remained elevated in 2. Arterial pH was maintained at normal levels throughout the experiments. Transpulmonary artery wedge pressure was similar during periods of ventilation with 21 % and 10% O2. Thus a hemodynamic basis for the increase in Cl prot. associated with hypoxemia is unlikely. These data indicate that PCP, which is already increased as a handicap of immaturity in pups, is further increased by severe hypoxemia. Similar studies are in progress on adult dogs. (SPR)