Electron-microscopic investigation of lung biopsies in patients with post-traumatic respiratory insufficiency

Lung biopsies were taken from patients during the course of post-traumatic respiratory insufficiency, from 3 hours to 19 days after the onset of shock. Electron-microscopic investigations revealed that the initial phases of cellular damaged were followed by both endothelial and epithelial changes, including atelectasis, lymphatic dilation, and interstitial as well as interalveolar fibrin extravasation. Interstitial edema and extravascular migration of granulocytes, lymphocytes and mast cells are followed by fibroblastic proliferation and, as an end result, fibrosis of the alveolar septa. As a result, fibroblasts replace capillaries at the surface, where gas exchange takes place. The capillaries are forced into the depths of the interstitial tissues. At the same time, the alveolar surface becomes covered with thick-walled proliferating epithelial cell layers, which also renders gas exchange increasingly difficult. Lung function is thereby reduced.