Effect of prolonged exposure to 80% oxygen on the lung of the newborn mouse.

Continuous exposure of newborn C57BL mice to 80% oxygen at normal atmospheric pressure for as many as 6 weeks results in significant pulmonary injury. This injury is reflected morphometrically and morphologically primarily in an increase in the pulmonary interstitial compartment and in pulmonary fibrosis. The fibrotic response is both peribronchiolar and parenchymal. Lowering the oxygen concentration of continuous exposure from 100 to 80% appears to reduce the cellular response of the alveolar lining cells and the bronchiolar mucosa in the newborn lung more than the fibrotic response. This suggests that the most persistent response in the growing lung to supplemental oxygen concentrations at or below 80% will be peribronchiolar and parenchymal fibrosis. These findings would account for the clinically observed reduction of stage II bronchopulmonary dysplasia, yet persistence of chronic bronchopulmonary dysplasia in human infants treated with supplemental oxygen concentrations below 100%.