Lung Surfactant and the Pathogenesis of Neonatal Bronchiolar Lesions Induced by Artificial Ventilation

Abstract

Summary: Premature newborn rabbits, obtained by hysterotomy on day 27 of gestation, were tracheotomized immediately after birth and treated with intermittent positive pressure ventilation (IPPV) for 16–60 min. Tidal volume was registered by means of a body plethysmograph and adjusted to 10 ml/kg and the insufflation pressure required to maintain this tidal volume was recorded. One group of animals received, by tracheal tube, a deposit of 50 μl homologous surfactant suspension, prepared by centrifugation of lung wash from adult rabbits (the phospholipid content of the surfactant suspension was 8.4 mg/ml, its lecithin content 6.9 mg/ml); littermates with empty tracheal tubes served as controls. The mean quasistatic compliance of the lung-thorax system was higher in surfactant-treated animals than in controls (0.42 ± 0.12 and 0.27 ± 0.04 ml/cm H<2<O Kg, respectively; <P< < 0.002). Alveolar expansion, determined morphometrically in histologie sections, was increased in animals receiving surfactant, in comparison with controls. Lung sections from control animals revealed widespread necrosis and desquamation of bronchiolar epithelium, whereas such lesions were scarce or absent in surfactant-treated animals. Our findings indicate that lung compliance of the premature neonate can be increased by deposition of surfactant in the upper airways before the onset of ventilation, and that deposition of surfactant prevents the development of bronchiolar epithelial lesions in premature neonates subjected to IPPV. Speculation: The possibility that administration of supplementary surfactant might serve as a prophylaxis against RDS and against epithelial lesions induced by artificial ventilation should be further evaluated in animal experiments and the clinical application of analogous prophylactic measures considered, once synthetic surfactant suspensions with optimal phospholipid (or phospholipid-protein) composition have been defined.