Hyaline membrane disease. Effect of surfactant prophylaxis on lung morphology in premature primates.

Neonatal lung morphology was evaluated in 12 rhesus monkeys delivered by caesarean section 1 month before term and cared for as human premature neonates. In 6 monkeys, 0.20 to 0.27 ml of natural rabbit surfactant (SA) was instilled intratracheally before the first breath; the other 6 served as controls. Histology and morphometry of the controls' lungs revealed changes typical of hyaline membrane disease (HMD) in human premature infants, whereas the SA-treated lungs showed improved alveolar expansion and only minor lesions typical of HMD. Transmission and scanning electron microscopy of the controls' lungs showed extensive necrosis and desquamation of bronchiolar epithelium, with formation of hyaline membranes; Type I alveolar epithelial cells showed lesions similar to those in bronchioles, but immature Type II cells appeared relatively well preserved. In the lungs of SA-treated animals, the epithelial lining of most airways and alveoli was intact. This first demonstration of the beneficial effect of exogenous SA on lung adaptation in premature primates indicates that prophylaxis with SA might prevent HMD in premature human infants.