I would like to thank Nancy Moreland for preparation of the manuscript. Data analysis was done in accordance with the standards of the Cochrane Neonatal Review Group. Main results All of the included studies note an initial improvement in respiratory status and a decrease in the risk of respiratory distress syndrome in infants who receive prophylactic natural surfactant extract. No differences are reported in the risk of intraventricular hemorrhage, patent ductus arteriosus, necrotizing enterocolitis or retinopathy of prematurity. Infants who receive prophylactic natural surfactant extract have a decreased risk of pneumothorax, a decreased risk of pulmonary interstitial emphysema, a decreased risk of mortality, and a decreased risk of bronchopulmonary dysplasia or death.
Surfactant lines the alveolar surface and prevents atelectasis at end expiration.
Pulmonary surfactant also contains neutral lipids and distinct surfactant proteins. The physiologic functions of surfactant include the ability to lower surface tension, and the ability to rapidly adsorb, spread and reform a monolayer in the dynamic conditions associated with the respiratory cycle. These investigators could not demonstrate any beneficial effect of surfactant replacement. The poor results were, in part, due to an incomplete understanding of what constitutes pulmonary surfactant. Enhorning administered a crude natural surfactant extract obtained from lavage of the lungs of mature rabbits directly into the trachea of immature rabbits.