Inhibition of Hypoxic Pulmonary Vasoconstriction by Nifedipine

SEVERE pulmonary hypertension mainly due to hypoxic vasoconstriction may develop in patients with chronic airflow obstruction and acute respiratory failure.1 Experiments in isolated rat lungs have implied that the calcium antagonist verapamil inhibits hypoxic pulmonary vasoconstriction.2 A preliminary report on patients with hypoxia suggests that verapamil causes an immediate drop in pulmonary vascular resistance.3 However, the concomitant fall in cardiac output may be hazardous in these severely hypoxic subjects. Nifedipine, a new calcium antagonist, causes few side effects4 and is a powerful vasodilating agent of systemic vessels5; as a result it usually increases cardiac output in both normal subjects . . .