Inhaled nitric oxide in chronic obstructive lung disease

During an investigation of the effect of nitric oxide on the pulmonary circulation the authors had the opportunity to give nitric oxide to a patient with longstanding obstructive airway disease, with successful results. A 72-year-old man with chronic obstructive pulmonary disease was referred to the institution for assessment of pulmonary vascular reactivity to acetylcholine and nitric oxide. Acetylcholine was infused into the main pulmonary artery followed 15 min later by an inhalation of 80 parts per million (ppm) nitric oxide. Heart rate and systemic arterial and pulmonary arterial pressures were continuously monitored. Throughout the study the inspired oxygen concentration was kept constant at 98%. Nitrogen dioxide and nitric oxide concentrations were monitored while nitric oxide was delivered. The infusion of acetylcholine resulted in a small increase in pulmonary artery pressure and pulmonary vascular resistance. Nitric oxide produced a substantial fall in pulmonary artery pressure and pulmonary vascular resistance with a concomitant increase in systemic arterial oxygen tension. These results suggest that endothelium-dependent relaxation of the pulmonary vasculature was impaired in the patient and that exogenous nitric oxide was an effective pulmonary vasodilator. In-vitro investigation of explanted airways disease suggests not only that endothelium-dependent pulmonary artery relaxation is impaired but alsomore » that the dysfunction is related to pre-existing hypoxemia and hypercapnia. Nitric oxide inhibits proliferation of cultured vascular smooth muscle cells and might alter the pulmonary vascular remodeling characteristic of patients with chronic obstructive airways disease.« less