To review the basic science, physiology, toxicity, and delivery of inhaled nitric oxide (NO).

A literature review of inhaled NO is presented, and a brief discussion of current clinical applications is included.

Inhaled NO is a new investigational drug used for selective vasodilation of the pulmonary vasculature. It mimics the effects of endogenously produced endothelium-derived relaxing factor. In addition to selective pulmonary vasodilation, inhaled NO can improve hypoxemia by improving ventilationperfusion relationships within the lung. The doses of inhaled NO that produce improvements in oxygenation are lower than those needed to produce maximal vasodilation. Inhaled NO is being used in the intensive-care unit to treat critically ill patients with pulmonary hypertension or hypoxemia associated with ventilation-perfusion imbalance. It is also being used in the cardiac catheterization laboratory as a diagnostic tool. Few adverse effects have been associated with the use of inhaled NO.

Despite a lack of randomized, controlled studies that show improved outcome in comparison with traditional treatments, inhaled NO. seems to be an effective new therapy for patients with pulmonary vasospasm or hypoxemia associated with ventilation-perfusion imbalance. It may also prove to be a valuable diagnostic tool in the cardiac catheterization laboratory.