Airway Epithelial Damage in Premature Infants with Respiratory Failure

To evaluate the evolution of airway epithelial damage in premature infants developing bronchopulmonary dysplasia (BPD), a detailed quantitative light and electron microscopic evaluation was performed of the major airways in 3 infants who succumbed from respiratory failure. The 3 infants ranged from 24 to 28 wk gestational age and died after 14 h, 10 days, and 6 months of life. The tracheal epithelium was severely damaged with up to half of the epithelium being denuded in each infant. The infants who died after 14 h and after 10 days demonstrated minimal epithelial denudation in more distal bronchial divisions. However, gross and microscopic abnormalities of the ciliated component of the epithelium were common. In the infant with severe established BPD, there was extensive epithelial denudation and ciliary abnormalities out to the fourth bronchial division. The percentage of goblet cells in the total cell population decreased from proximal to distal major airways, with the lowest percentage being seen in the infant with established BPD. These studies demonstrate the respiratory failure and assisted ventilation in the human neonate is associated with severe epithelial damage in the trachea and proximal bronchi. It suggests that the difficulty in clearing airway secretion results from a defect in mucociliary transport system rather than from an increase in airway secretion.