Pulmonary oxygen toxic effect. Occurrence in a newborn infant despite low Pa(O₂) due to an intracranial arteriovenous malformation

A newborn infant with a massive left to right shunt secondary to a cerebral arteriovenous malformation required continuous oxygen therapy in high concentrations. Despite high P(O₂), the infant maintained low to normal Pa(O₂) concentrations. Light and ultrastructural studies of the lungs demonstrated typical changes of acute pulmonary oxygen toxicity, including degeneration of capillary endothelium and type I pneumonocytes, interstitial edema, and alveolar exudation. These observations confirm earlier experimental animal studies that demonstrated that the alveolar P(O₂) concentration and not the Pa(O₂) is the major factor contributing to pulmonary oxygen toxic effect.