Immaturity and Enhanced Susceptibility to Acute Hemodynamic Pulmonary Edema

Abstract

The hypothesis that the immature lung is more susceptible than the mature lung to the development of acute pulmonary edema (PE), was tested by determining the transmural hydrostatic pressure in excess of whole blood colloid osmotic pressure (COP) necessary to produce PE in pups and adult dogs. Ten pups and ten adults were anesthetized with pentobarbital, parpalyzed with succinylcholine, and artifically ventilated. Transmural pulmonary artery wedge pressure (TPAWP) (as a reflection of vascular filtration pressure) was monitored continuously and whole blood COP intermittently. A balloon catheter in the thoracicaorta was inflated to produce an elevation of TPAWP in relation to COP that was maintained for 30 min by infusion of isosmotic dog blood to maintain a constant differential pressure (TPAWP-COP). Lungs were then removed and thed degree of PE assessed by gross microscopic appearance and determination of water content. Interstitial edema first appeared with thw following range odf values: Gross edema formed at higher differentiak pressures. Thus the pups developed minimal PE at lower TPAWP than would have been expected from their T.P. and COP. The data do not permit a choice of the several factors that might explain this finding. Similar susceptibility of the human fetus and newborn in relation to the adult would favor the development of PE during the perinatal period and might thus play a role in the pathogenesis of pulmonary problems of the newborn.