Pulmonary Surfactant — An Overview

Pulmonary surfactant is a complex of lipids — principally phospholipids — proteins, and carbohydrates which line the surface of lung alveoli and respiratory bronchioles. Its functions appear to be multiple (see Section III below), but its principal role, the one which has led to its discovery, is related to lung mechanics and alveolar stability. The importance of its functional significance is illustrated by the fact that surfactant deficiency, the major cause of which is lung immaturity in the prematurely delivered newborn, leads to neonatal respiratory distress syndrome (RDS), otherwise designated hyaline membrane disease (HMD). The latter represents in developed countries the first cause of neonatal mortality and morbidity. ¹ Although not presenting as an initial cause, but rather as a secondary aggravating factor, surfactant deficiency is also involved in the pathogenesis of adult respiratory distress syndrome. ²