INCREASED AMOUNT OF NITRIC-OXIDE IN EXHALED AIR OF ASTHMATICS

The presence of nitric oxide (NO) in the exhaled air of humans has rec ently been described. We wanted to assess at what level exhaled NO ori ginates in normal airways, and to determine whether airway inflammatio n induces changes in the levels of exhaled NO. Exhaled NO was continuo usly measured by chemiluminescence technique during normal tidal breat hing through the nose or mouth, with a detection limit of 1 part per b illion (ppb). Twelve control subjects were compared to eight patients with mild atopic asthma and rhinitis caused by occupational allergen. In control subjects, the major part of NO in exhaled air (up to 30 ppb ) seemed to originate in the nasal airways, with only minor contributi on from the lower airways and the oral cavity. However, in mild asthma tics, the level of exhaled NO during oral breathing, indicating the in volvement of the lower airways, was increased 2-3 fold. Since increase d production of NO in the lower airways may involve activated macropha ges or neutrophils, we suggest that exhaled NO may be used to instantl y monitor ongoing bronchial inflammation, at least when involving indu cible NO synthase.