LUNG LYMPH STUDIES IN NEWBORN LAMBS WITH HYALINE MEMBRANE DISEASE (HMD):

HMD is associated with clinical evidence of pulmonary edema. Previous studies have shown that lungs from lambs with HMD have increased extravascular water content and decreased permeability-surface area (PS) for 14C Urea indicating a decreased surface area (Pediatr. Res. 15:731, 1981). In order to examine if increased vascular permeability is present in HMD, lung lymph was collected from 5 lambs with histologically confirmed diagnosis of HMD and from 5 lambs without HMD. All lambs were delivered prematurely (0.87 to 0.95 of term gestation) by cesarean section and were studied for 2 hours before and 4 hours after birth. Normalized to fetal values, mean lymph flow (QL) trippled at 1 hour after birth in lambs without HMD and decreased thereafter to 1.6 times the fetal value. QL in HMD lambs increased progressively to 3.3 times the fetal value. Mean lymph/plasma protein ratio decreased with time in both groups of lambs. Lymph protein clearance (CLP) for total protein and smaller protein fractions increased progressively in lambs with HMD but decreased between 1 and 4 hours in lambs without HMD. Post mortem lung water was higher in lambs with HMD. At 3 and 4 hours after birth, lambs with HMD had significantly* higher QL and CLP, equal lymph/plasma ratios and only slightly higher pulmonary arterial pressure. These results combined with the earlier reported decreased surface area in HMD would indicate delayed fetal lung fluid absorption and increased vascular permeability for proteins in pulmonary exchange vessels in lambs with HMD. *p <0.05 (Supported by HL 14214)