Bronchodilator effect of inhaled nitric oxide in healthy men.

Studies in animals have shown that inhalation of nitric oxide (NO) either reduced pulmonary resistance after an induced bronchospasm or protected animals from bronchoconstriction. To evaluate whether NO inhalation (80 parts per million) influences basal bronchial tone or reverses methacholine-induced bronchospasm, we determined specific airway conductance (SGaw) as a measure of airway caliber in seven healthy men. After methacholine-induced bronchoconstriction NO increased SGaw by 23% (p < 0.05). One week later, NO inhalation did not change baseline SGaw values. However, albuterol inhaled after NO, or on a separate day, significantly increased SGaw (p < 0.05). The bronchodilator effect of NO in men with methacholine-induced bronchospasm is much less than that reported in animals or that regularly observed in asthmatic patients after the inhalation of beta-sympathomimetic drugs.