Extended exhaled NO measurement differentiates between alveolar and bronchial inflammation

Lower respiratory tract inflammation can be detected by measuring exhaled n itric oxide (NO) concentration at a single exhalation flow rate, but this d oes not differentiate between alveolar and bronchial NO production. We asse ssed alveolar NO concentration and bronchial NO flux with an extended metho d of measuring exhaled NO at several exhalation flow rates in 40 patients w ith asthma, 17 patients with alveolitis, and 57 healthy control subjects. B ronchial NO flux was higher in asthma (2.5 +/- 0.3 nl/s, p < 0.001) than in alveolitis (0.7 +/- 0.1 nl/s) and healthy control subjects (0.7 + 0.1 nl/s ). Alveolar NO concentration was higher in alveolitis (4.1 +/- 0.3 ppb, p < 0.001) than in asthma (1.1 +/- 0.2 ppb) and healthy control subjects (1.1 +/- 0.1 ppb). In asthma, bronchial NO flux correlated with serum level of e osinophil protein X (EPX) (r = 0.60, p < 0.001) and bronchial hyperresponsi veness (r = 0.55, p < 0.001). In alveolitis, alveolar NO concentration corr elated inversely with pulmonary diffusing capacity (r = -0.55, p = 0.022) a nd pulmonary restriction. Glucocorticoid treatment or allergen avoidance no rmalized bronchial NO flux in asthma and decreased alveolar NO concentratio n toward normal in alveolitis. In conclusion, extended exhaled NO measureme nt can be used to separately assess alveolar and bronchial inflammation and to assess disease activity/severity in asthma and alveolitis.