Effect of aerosolized prostacyclin and inhaled nitric oxide on experimental hypoxic pulmonary hypertension

Objective: To compare the effect of different concentrations of inhaled nitric oxide and doses of nebulized prostacyclin on hypoxia-induced pulmonary hypertension in pigs. Design: Prospective, controlled animal study. Setting: Animal research facilities of an university hospital. Interventions: After reducing the fraction of inspired oxygen (FIO2) from 1.0 to 0.1, two groups of five pigs each were submitted to inhalation of three concentrations of nitric oxide (5, 10 and 20 ppm) or three doses of prostacyclin (2.5, 5, 10 ng x kg(-1) x min(-1)). Results: All doses of prostacyclin and concentrations of nitric oxide resulted in a decrease in mean pulmonary arterial pressure and pulmonary vascular resistance when compared to hypoxic ventilation (p < 0.001) which was independent of the dose or concentration of either drug used. While inhalation of nitric oxide caused a reduction in mean pulmonary arterial pressure back to values obtained during ventilation with FIO2 1.0, values achieved with prostacyclin were still significantly higher when compared to measurements prior to the initiation of hypoxic ventilation. However, direct comparison of the effect of 20 ppm nitric oxide and 10 ng x kg(-1) x min(-1) prostacyclin on mean pulmonary arterial pressure revealed no differences between the drugs. All other hemodynamic and gas exchange parameters remained stable throughout the study. Conclusions: Inhalation of clinically used concentrations of nitric oxide and doses of prostacyclin can decrease elevated pulmonary arterial pressure in an animal model of hypoxic pulmonary vasoconstriction without impairing systemic hemodynamics or gas exchange.