Effect of Inhaled Prostacyclin in Combination with Almitrine on Ventilation-Perfusion Distributions in Experimental Lung Injury

Background: Inhaled prostacyclin and intravenous almitrine have both been shown to improve pulmonary gas exchange in acute lung injury (ALI). This study was performed to investigate a possible additive effect of prostacyclin and almitrine on pulmonary ventilation-perfusion (a/) ratio in ALI compared with inhaled prostacyclin or intravenous almitrine alone.

Methods: Experimental ALI was established in 24 pigs by repeated lung lavage. Animals were randomly assigned to receive either 25 ng middle dot] kg-1 middle dot] min-1 inhaled prostacyclin alone, 1 mu]g middle dot] kg-1 middle dot] min-1 almitrine alone, 25 ng middle dot] kg-1 middle dot] min-1 inhaled prostacyclin in combination with 1 mu]g middle dot] kg-1 middle dot] min-1 almitrine, or no specific treatment (controls) for 30 min. For each intervention, pulmonary gas exchange and hemodynamics were analyzed and a/ distributions were calculated using the multiple inert gas elimination technique. The data was analyzed within and between the groups by analysis of variance for repeated measurements, followed by the Student-Newman-Keuls test for multiple comparison when analysis of variance revealed significant differences.

Results: All values are expressed as mean +/- SD. In controls, pulmonary gas exchange, hemodynamics, and a/ distribution remained unchanged. With prostacyclin alone and almitrine alone, arterial oxygen partial pressure (Pao2) increased, whereas intrapulmonary shunt (S/T) decreased (P < 0.05). Combined prostacyclin and almitrine also increased Pao2 and decreased S/T (P < 0.05). When compared with either prostacyclin or almitrine alone, the combined application of both drugs revealed no additional effect in gas exchange or a/ distribution.