Nitric oxide: a selective pulmonary vasodilator.

Nitric oxide (NO) has recently been found to be the endothelium-derived factor that produces profound relaxation of the vascular smooth muscle. This discovery has led to the experimental use of inhaled NO as a selective pulmonary vasodilator without concomitant systemic vasodilation. Currently, clinical trials of inhaled NO in persistent pulmonary hypertension of the newborn (PPHN) are in progress. Inhaled NO has also been used in the adult respiratory distress syndrome (ARDS). The therapeutic role, if any, of inhaled NO in other diseases featuring pulmonary hypertension remains unknown. Further research is needed to determine potential toxic effects of NO, development of delivery systems, and monitoring techniques applicable to routine clinical care.