Oxygen toxicity in the infant rhesus monkey lung. Light microscopic and ultrastructural studies

Eight monkeys were anesthetized with ketamine hydrochloride and positive pressure ventilated with greater than 95% oxygen (tests) or room air (controls) for 24 hours. Two test monkeys and one control were treated with E. coli endotoxin (500 micrograms/kg) IV at the start of the study and after 12 hours. Histopathological changes in the lung parenchyma were evaluated using light and electron microscopy. Interstitial edema was detected as early as 24 hours after the onset of hyperoxia but there was no significant increase in the alveolar-capillary distance (blood-air barrier). Morphologic signs of oxygen toxicity further included swelling and disruption of vascular endothelium, and swelling of alveolar Type II pneumocytes. There was no difference in the number of macrophages per high power field between the four groups but significant differences were observed in the number of neuroepithelial bodies (NEBs) per cm2 and mast cells per high power field at the light microscopic level. Treatment with endotoxin did not protect against oxygen toxicity and was associated with an exacerbation of the morphological alterations in the lung parenchyma and swelling of alveolar Type I pneumocytes.