Figure 1.

Examples of vascular lesions resulting from deforming stress. (A) Images of the blood–gas barrier (i.e., intraalveolar capillaries) of rats exposed to injurious mechanical ventilation. Note endothelial (A1) and epithelial (A2) blebbing and gaps that are marked by arrows. AS = alveolar space; IE = interstitial edema; PN = polymorphonuclear neutrophil. (Reproduced with permission from Dreyfuss D, et al. Principles and Practices of Mechanical Ventilation. New York: McGraw-Hill, 1994. pp. 793–811.) (B) Images of the blood–gas barrier of rabbits with hydrostatic pulmonary edema. Note blebbing and vesicle formation (B1and B2, thin arrows and asterisks) as well as the large alveolar fenestration with denuded/exposed basement membrane (B3, wide arrow). AE = alveolar edema; BM = basement membrane; End = endothelium. (B1 and B2 reproduced with permission from Reference 54; B3 reproduced with permission from Reference 25.) (C) Images of two adherent endothelial cells (red and yellow) from a frog mesenteric capillary that is exposed to high vascular pressures. Upper panel = en-face view; lower panel = cross-section. Note the intracellular gap formation (G1) and the preserved intercellular tight junction. (Reproduced with permission from Reference 89.) (D) Scanning electron-micrograph of an intraalveolar pulmonary capillary from a mechanically ventilated patient with acute respiratory distress syndrome (D1). Note that the capillary/basement membrane fracture (D2 is magnified view). (Reproduced with permission from Reference 80.)