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 through a pulmonary artery catheter into an acinar region with occluded blood flow and measuring Xe-133 washout by gamma scintillation scanning. We measured washout in six anesthetized paralyzed dogs during mechanical ventilation with O-2 before and after injection of 0.6 mg/kg of oleic acid into the right atrium, which induces severe pulmonary edema within 2 h. Changes in the elastance and resistance of the lung were also calculated from measurements of airway flow, airway pressure, and esophageal pressure. Before injection of oleic acid, the monoexponential rate constant for Xe-133 washout was 3.6 +/- 1.4 (SE) min(-1); from this we estimated that the rate of gas transfer of Xe-133 from the acini was 1.0 l/min. The rate constant decreased gradually after the injection and was correlated with increases in elastance and resistance (r = -0.66) and decreases in alveolar Po, (r = 0.71). At 2 h after injection, 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 <0.32 l/min. We conclude that resistance in the acini is increased during pulmonary edema and that it is correlated, in the oleic acid model, with changes in overall lung mechanical properties.