[Oxygen toxicity for pulmonary parenchyma. Ultrastructural study by electron microscopy. Physiopathologic data].

The lungs of rats submitted to 24, 36, 48 and 72 hours of pure normobaric oxygen were examined by means of the scanning microscope. The images obtained give a dynamic aspect of the changes in the lesions with two distinct phases: a phase of reactivity at 48 hours, marked by the development of hyperactivity of the granular pneumocytes, a phase of destruction characterised by considerable changes in the alveolar epithelium and filling in of the alveolar lumen with various debris. From these morphological findings, different physio-pathological factors are discussed: the role of the increase in PaO2, the protection provided by the increase in the gradient (A - a) DO2, cerebral and adrenal medullary involvement especially in hypoxemic subjects.