1728 LUNG WATER AND VASCULAR PERMEABILITY-SURFACE AREA IN LAMBS WITH HYALINE MEMBRANE DISEASE (HMD)

Abstract

HMD is associated with increased intrapulmonary shunting and clinical evidence of increased vascular permeability. Multiple-tracer methods were used to measure vascular permeability-surface area (PS) for ¹⁴C-urea using the integral extraction method in premature newborn lambs delivered by cesarean section (CS). Fourteen studies were performed during the first 7 hours after birth in 7 HMD lambs delivered at 127-133 days of gestation using ⁵¹Cr-erythrocytes, ¹²⁵I-albumin and ¹⁴C-urea. Pulmonary blood flow was corrected for extra-pulmonary shunts using a flowcuff and microspheres. Extravascular lung water content (ELW) was measured post mortem with a ⁵¹Cr-erythrocyte method. The results were compared with those from 12 identical studies in 5 lambs without HMD delivered by CS around 140 days. Normalized to dry lung weight, the data expressed as mean ± S.E.M. were as follows:

Normalized this way, lung water was significantly greater in the HMD lambs. PS values were significantly lower in the HMD lambs and showed a significant^* decrease with postnatal age. PS was inversely correlated to pulmonary vascular resistance (r=0.67^*). These data indicate that pulmonary edema and derecruitment occurs in HMD resulting in decreased surface area for exchange. ^*p<0.05

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