Sequential changes of perivascular edema cuffs in models of permeability and hemodynamic pulmonary edema

The areas of perivascular edema cuffs surrounding pulmonary arteries and veins were sequentially measured as an index of the fluid transport unit in lung interstitium (FTULI) in epinephrine-induced and oleic acid-induced pulmonary edema in rats. The former edema represents a model of hemodynamic edema and the latter, permeability pulmonary edema, respectively. In epinephrine-induced pulmonary edema, both the ratio of edema cuff area to cross-sectional area of the pulmonary artery (Rr) and the ratio of lung weight to body weight (L/B) were increased in parallel, reached maximum levels at 0.5 h after the treatment, and returned to the control levels after 3 h. In oleic acid-induced pulmonary edema, the changes in Rr and L/B were not parallel, and the maximum levels were reached at different times, Rr at 3 h and L/B at 1.5 h. Rr returned close to the control level in 24 h but L/B remained elevated so that rate of recovery was delayed. The cuffs around the veins appeared similar to those around the arteries, but were very slight in both models. The difference in the time course of Rr and L/B in the two models may suggest that the recruitment of FTULI is insufficient in oleic acid-induced pulmonary edema; this limitation seems to be an important factor which makes the permeability edema refractory to treatment, together with the damage to the blood gas barrier.