The surfactant system and structure of the respiratory portion of the lungs during de-adaptation following a single exposure to acute pressure chamber hypoxia

The effect of acute pressure chamber hypoxia on the surfactant system and respiratory segment structure of the lungs were studied in rats by physical, fluorescent microscopic and morphometric methods. Acute hypoxia decreases surface activity, induces changes in cellular and extracellular surfactant fluorescence and causes the development of diffuse vesicular emphysema. On the first day of adaptation atelectatic foci dominate over emphysema, and the pulmonary structure normalizes afterwards. During de-adaptation, surface activity and cellular surfactant fluorescence are higher than the control levels. Surface activity and extracellular surfactant fluorescence recover steadily by the fifth day of adaptation. The amount of phagocytized surfactant in alveolar macrophages is increased, with the changes being opposite to those characteristic of extracellular surfactant.