Different patterns of exhaled nitric oxide response to [beta]2-agonists in asthmatic patients according to the site of bronchodilation

Background In asthmatic patients undergoing airway challenge, fraction of exhaled nitric oxide (Feno) levels decrease after bronchoconstriction. In contrast, model simulations have predicted both decreased and increased Fenolevels after bronchodilation, depending on the site of airway obstruction relief. Objective We sought to investigate whether β2-agonists might induce divergent effects on Fenovalues in asthmatic patients as a result of airway obstruction relief occurring at different lung depths. Methods Feno, FEV1, and the slope of phase III of the single-breath washout test (S) of He (SHe) and sulfur hexafluoride (SSF6) were measured in 68 asthmatic patients before and after salbutamol inhalation. SHeand SSF6decreases reflected preacinar and intra-acinar obstruction relief, respectively. Changes (Δ) were expressed as a percentage from the baseline. Results No Fenochange (|ΔFeno|