Scanning electron microscopy of epithelial lesions induced by artificial ventilation of the immature neonatal lung; the prophylactic effect of surfactant replacement.

Immature newborn rabbits, delivered on day 27 of gestation were ventilated artificially for 5-10 min with a peak insufflation pressure of about 35 cm H2O, with or without previous treatment with natural surfactant via the airways. The alveolar expansion pattern and the surface structure of the airways were then examined by scanning and transmission electron microscopy. Animals not receiving surfactant had very irregular alveolar expansion and showed prominent desquamation of the bronchiolar epithelium with a strikingly ragged appearance of the mucosa in the scanning electron microscopic images. Litter mates treated with surfactant had improved alveolar expansion and a flattened but otherwise nearly intact bronchiolar epithelium. The findings confirm the beneficial effect of surfactant replacement on the immature neonatal lung.