EFFECT OF PULMONARY-EDEMA ON TRANSFER OF GAS FROM ACINUS TO AIRWAYS

We directly measured the effect of progressive pulmonary edema on gas transfer from the acinus by injecting Xe-133 dissolved in saline throu gh a pulmonary artery catheter into an acinar region with occluded blo od flow and measuring Xe-133 washout by gamma scintillation scanning. We measured washout in six anesthetized paralyzed dogs during mechanic al ventilation with O-2 before and after injection of 0.6 mg/kg of ole ic acid into the right atrium, which induces severe pulmonary edema wi thin 2 h. Changes in the elastance and resistance of the lung were als o calculated from measurements of airway flow, airway pressure, and es ophageal pressure. Before injection of oleic acid, the monoexponential rate constant for Xe-133 washout was 3.6 +/- 1.4 (SE) min(-1); from t his we estimated that the rate of gas transfer of Xe-133 from the acin i was 1.0 l/min. The rate constant decreased gradually after the injec tion and was correlated with increases in elastance and resistance (r = -0.66) and decreases in alveolar Po, (r = 0.71). At 2 h after inject ion, the rate constant (1.2 +/- 0.8 min-l) was lower than control (P < 0.01), and the rate of gas transfer of Xe-133 from the acini was <0.3 2 l/min. We conclude that resistance in the acini is increased during pulmonary edema and that it is correlated, in the oleic acid model, wi th changes in overall lung mechanical properties.