Ultrastructural substrates for increased lung water content in experimental pulmonary edema.

We examined the relationship between the incidence of ultrastructural changes in the alveolar septum and the extravascular lung water content. Pulmonary edema was induced in 18 mongrel dogs by either dextran (n = 12) or alloxan (n = 6) administration. Six other dogs served as controls. Extravascular lung water content was measured by the thermal-dye double indicator dilution method. Specimens of lung tissue were examined with an electron microscope, and the incidence of 13 types of pathological changes in the alveolar septum was studied. For each type of pathological change, the incidence was correlated with the magnitude of lung water content. The following results were obtained. The incidence of edematous changes in the alveolar interstitium (widening of the interstitial space, and dispersion and disarray of collagen fibres in the interstitial space) was well correlated with lung water content (r = 0.78, p < 0.01, and r = 0.84, p < 0.01, respectively). The correlation was not significant in the remaining types of changes. We conclude that the incidence of the pathological changes in the alveolar septum is increased along with the increase in the content of lung water in both dextran- and alloxan-induced experimental pulmonary edema in dogs.