The role of nitric oxide in respiratory disease.

Nitric oxide (NO) is found in both the upper and lower airways of man. In the lower airways it is found at concentrations less than 3 ppb, and in the upper airways at about 400 ppb. The NO found in the upper airways is thought to play a role in maintaining the sterility of the paranasal sinuses. NO is also produced by the endothelium of the pulmonary vasculature. Endothelium-derived NO is a potent vasodilator involved in maintaining low pulmonary tone. Impaired endothelial NO production is thought to be involved in some types of pulmonary hypertension. When inhaled, NO acts as a selective pulmonary vasodilator which is used to treat respiratory diseases. One area in which NO has proven to be particularly effective is in the treatment of persistent pulmonary hypertension of the newborn. Inhaled NO therapy can be used in the treatment of adult respiratory distress syndrome, primary pulmonary hypertension and chronic obstructive pulmonary disease.