Electron Microscopic and Morphometric Study of Rats Exposed to 98.5 Percent Oxygen at Atmospheric Pressure

摘要

Rats were exposed to 98.5% oxygen at 765 Torr in a controlled environmental chamber. Groups were sacrificed at 6, 24, 48, and 72 hours and the lungs were prepared for light and electron microscopic examination. A control group breathed room air. In the groups which breathed oxygen for 6 and 24 hours no changes in lung structure could be observed. After 48 hours the interstitial space was enlarged by accumulation of fluid and early destructive changes of the capillary endothelial lining were found. After 72 hours the widened interstitial space contained numerous leucocytes, thrombocytes and other cells; fibrin strands were numerous. There was marked destruction of the pulmonary capillaries. At this stage, 65% of all alveoli were filled with an exudate containing leucocytes, erythrocytes, macrophages and fibrin strands. There was a decrease in capillary blood volume and of endothelial surface after 72 hours. The thickness of the air-blood barrier was increased after 48 and doubled after 72 hours. The barrier thickening was mainly due to increase of the interstitial space; terminally, the epithelium was also thickened, although the endothelium became thinner, on the average, due to destruction. As a result of these alterations there was a marked fall in estimated gas exchange capacity of the air-blood tissue barrier. (Author)