The effect of bronchodilation and spirometry on fractional exhaled nitric oxide (FeNO50), bronchial NO flux (JawNO) and alveolar NO concentration (CANO) in children and young adults

Objective: Fractional exhaled nitric oxide (FeNO), bronchial nitric oxide (JawNO) and alveoar nitric oxide (C_ANO) are biomarkers of eosinophilic inflammation, usually measured simultaneously with spirometry and bronchodilation. Our aim was to investigate the effect of bronchodilation and spirometry on FeNO, C_ANO and JawNO in children and young adults with well-controlled asthma and in healthy volunteers. Methods: FeNO was measured in 95 subjects (62 controls, 33 asthmatics). C_ANO and JawNO were assessed in 41 of the subjects (35 healthy, 6 asthmatics.) Measurements were performed before spirometry (1), right after spirometry (2), 20 min after the first spirometry and bronchodilation (3), right after the post-bronchodilation spirometry (4) and 30 min after the last spirometry (5). Results: The presence of well-controlled asthma was not associated with different pattern of reaction after spirometry and bronchodilation. A statistically significant difference was observed only between FeNO4 and FeNO5, as well as between C_ANO1 and C_ANO3 (19.14 ± 1.68 vs 20.62 ± 1.85 ppb, p = 0.001 and 4.42 ± 0.40 vs 3.09±0.32 ppb, p = 0.001, respectively). Conclusions: Spirometry and bronchodilation have an insignificant effect on FeNO and JawNO. Even if a slight change occurs in FeNO and JawNO, this does not modify clinician's decision and therapeutic strategy. C_ANO values (C_ANO1) are significantly decreased 20 min after spirometry and bronchodilation.