Pulmonary surfactant. I. In immature and mature babies

Lung surfactant was obtained by postmortem lavage from: (A) premature babies: 34 dying acutely within 2 days of birth from Hyaline Membrane Disease (HMD), 20 dying several days after birth with HMD and its consequences, 8 dying from causes other than HMD; (B) mature babies: 24 dying stillborn, 15 dying soon after birth and 16 dying between 2 weeks and 1 year of age with minimal lung pathology. The phospholipid composition of the surfactant was analysed. Compared to the surfactant of babies dying acutely from HMD, that of the babies dying later from HMD contained significantly higher proportions of phosphatidylcholine (PC) and significantly lower proportions of sphingomyelin while that of the mature babies contained significantly higher proportions of PC and phosphatidylglycerol but significantly lower proportions of sphingomyelin and combined phosphatidylinositol and phosphatidylserine. The surfactant of premature babies dying of causes other than HMD was similar and intermediate to that of both groups of babies dying from HMD. The PC fraction composition of the surfactant of the babies dying acutely from HMD contained significantly lower proportions of the disaturated fraction than those of the babies dying later from HMD, stillborn babies or mature babies.