Objective: To explore the dose-response relationship in patients with pulmonary hypertension after inhalation of nitric oxide (NO).
Methods: The effect of various concentrations (20, 40, 60 and 80 ppm) of NO on hemodynamics and cardiac function in 16 patients with pulmonary hypertension was studied with right heart catheterization.
Results: Pulmonary artery pressure and pulmonary vascular resistance reduced significantly after inhalation of various concentrations (20, 40, 60 and 80 ppm) of NO. The vascular response to NO was not concentration-dependant with a maximal effect obtained at 20 ppm. At inhalation of low dose of NO (20 ppm), the mean pulmonary artery pressure and pulmonary vascular resistance dropped by 26.5% and 40.3% (P < 0.0001), respectively. With the increase of inhaled NO concentration, pulmonary artery pressure and pulmonary vascular resistance did not decline.
Conclusion: The best concentration of inhaled NO was not more than 20 ppm in the patients of this study.