M Bachofen

Eight normal human lungs obtained from patients dying from causes not related to the lung were subjected to morphometric analysis to determine the number of cells in the alveolar region and their mean volume and surface characteristics. The age range was 19 to 40 yr, average body weight was 74 kg, and the average fixed lung volume was 4,300 ml. The overall mean nuclear diameters of the nuclei of 5 major cell types in the lung parenchyma were found to have little variation, with means ranging from 7.54 to 8.77 micrometers. Alveolar type I epithelial cells were found to comprise 8% of the cells and to be one of the largest cells, having a mean volume of 1,764 micrometers 3 and covering an average of 5,098 micrometers 2 of alveolar surface. Seven percent of the alveolar surface was covered by alveolar type II cells, which make up 16% of the total alveolar cells and have a mean volume that is half that of the type I pneumocyte. Capillary endothelial cells make up 30% of the lung cells and were significantly smaller in both size and average surface area than the alveolar type I cells. Cells in the interstitial space comprised 37% of the total cells. The number of alveolar macrophages showed great variability, ranging from 19% of alveolar cells in 1 person to 3 to 5% in the nonsmoking females. The alveolar cell population characteristics found in resected lobes from 2 nonsmoking females were found to be similar to 2 nonsmoking females studied after autopsy. An interspecies comparison of characteristics of cells from the alveolar regions of normal lungs from humans, baboons, and rats showed that proportions of cells in the alveolar region and their average thickness, size, and surface areas were relatively constant.

Abstract Lung tissue from 9 patients dying in different stages of an acute respiratory distress syndrome due to septicemia was fixed by a postmortem transthoracic injection method for an ultrastruc-tural and morphometric analysis. At the initial stage of septic lung disease a widespread interstitial and alveolar edema was the essential finding. The capillary endothelium was relatively well preserved; in particular, no large endothelial gaps could be detected. In contrast, local destruction of the squamous epithelium, often covered by hyaline membranes, and a rapid proliferation of Type II epithelial cells were noted. In the subacute stage, cuboidal transformation of the epithelium and fibrotic alterations of the interstitium were the predominant findings. The extent of fibrotic alterations of lung architecture was not clearly related to the time course of the disease; on the other hand, the thickening of the air-blood barrier estimated by morphometry mirrored the disturbances of gas exchange and lung mechanics. The nonspecificity of the lesions observed in the subacute as well as in the acute stage of the disease provided further evidence of a uniform and characteristic reaction pattern of the lung that does not reflect the type and route (via blood or inspired air) of the damaging agents. Hence, it appears questionable whether lung biopsy specimens obtained from patients with acute respiratory distress syndrome can contribute to the diagnosis of the underlying disease.