Impaired right-ventricular function may benefit from afterload reduction. Inhalation of nitric oxide (NO) reduces pulmonary hypertension without systemic circulatory depression. Influence of NO inhalation on oxygenation, ventilation, and hemodynamic parameters in 10 patients with acute pulmonary hypertension after cardiac surgery was examined in this study. Ten patients without NO treatment served as a control group. NO patients showed significantly improved oxygenation and recovery of right-ventricular function. Pulmonary artery pressure (12.8%), inspiratory oxygen demand (34.7%), PEEP (13.2%), and inspiration time (18.8%) decreased significantly during inhalation of nitric oxide. Mortality in both groups was identical. We therefore conclude that NO, by improving oxygenation and right-ventricular function, temporarily reduces invasiveness of mechanical ventilation. Reduction of invasiveness of ventilation did not influence mortality as compared with patients who did not receive NO. To finally estimate the benefit of NO inhalation, larger patient groups need to be examined.