Inhaled nitric oxide in the treatment of hypoxemic respiratory failure

Inhaled nitric oxide (iNO) is a pulmonary vasodilator that recruits blood flow to well-ventilated lung areas in the presence of lung disease. iNO may improve oxygenation by decreasing intrapulmonary shunt or may worsen oxygenation by reversing hypoxic pulmonary vasoconstriction, therapy increasing ventilation-perfusion mismatch. Recent studies have examined the mechanisms for gas exchange alterations with iNO. Moreover, several randomized controlled trials have explored the magnitude of the effect on oxygenation and the beneficial influence on clinical outcome in neonatal patients with hypoxemic respiratory failure. It is not known to what extent an increase in oxygenation affects clinical outcome in older patients. The potential benefit of iNO therapy must be weighed against the potential risks of inactivating surfactant and platelet function as well as influencing endogenous pulmonary vasoregulation. Well-designed studies will be important to determine whether the improvement in oxygenation outweighs these as well as unknown risks.