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 s hown to improve pulmonary gas exchange in acute lung injury (ALI). This stu dy was performed to investigate a possible additive effect of prostacyclin and almitrine on pulmonary ventilation-perfusion ((V) overdot/(Q) overdot)) ratio in ALI compared with inhaled prostacyclin or intravenous almitrine a lone. Methods: Experimental ALI was established in 24 pigs by repeated lung lavag e. Animals were randomly assigned to receive either 25 ng.kg(-1).min(-1) in haled prostacyclin alone, 1 mug.kg(-1).min(-1) almitrine alone, 25 ng.kg(-1 ).min(-1) inhaled prostacyclin in combination with 1 mug.kg(-1).min(-1) alm itrine, or no specific treatment (controls) for 30 min. For each interventi on, pulmonary gas exchange and hemodynamics were analyzed and (V) over dot/ (Q) over dot distributions were calculated using the multiple inert gas eli mination technique. The data was analyzed within and between the groups by analysis of variance for repeated measurements, followed by the Student-New man-Keuls test for multiple comparison when analysis of variance revealed s ignificant differences. Results: All values are expressed as mean +/- SD. In controls, pulmonary ga s exchange, hemodynamics, and (V) over dot A/(Q) over dot distribution rema ined unchanged. With prostacyclin alone and almitrine alone, arterial oxyge n partial pressure (Pao,) increased, whereas intrapulmonary shunt ((Q) over dot (S)/(Q) over dot (T)) decreased (P < 0.05). Combined prostacyclin and almitrine also increased Pao, and decreased (Q) over dot (S)/(Q) over dot ( T) (P < 0.05). When compared with either prostacyclin or almitrine alone, t he combined application of both drugs revealed no additional effect in gas exchange or (V) over dot A/(Q) over dot distribution. Conclusions: The authors conclude that, in this experimental model of ALI, the combination of 25 ng.kg(-1).min(-1) prostacyclin and 1 mug.kg(-1).min(- 1) almitrine does not result in an additive improvement of pulmonary gas ex change or (V) over dot/(Q) over dot distribution when compared with prostac yclin or almitrine alone.