Oxygen toxicity in the newborn. The effect of chronic continuous 100 percent oxygen exposure on the lungs of newborn mice.

Continuous exposure of newborn mice of a single, highly inbred strain to 100% oxygen at normal atmospheric pressure for up to 6 weeks resulted in a progressive evolution of pulmonary changes which consisted of dense fibrous tissue deposition, chronic bronchitis and bronchiolitis, and emphysema. Survival of the experimental animals decreased with the duration of exposure, and it was 18% after the sixth week. While the pulmonary changes were evolving, lung growth was markedly inhibited in the experimental animals, whereas lung weight increased significantly. The present study indicates that in contrast to the adult mouse, survival of a substantial percentage of newborn mice for at least 6 weeks is possible, but it is associated with severe changes in pulmonary structure that doubtlessly lead to serious derangement of cardiopulmonary functions.