Objective: The effect of spirometric maneuvers on exhaled nitric oxide (NO) at the constant flow rate of 50 ml/s (FE(NO)) has been studied with equivocal results. Furthermore, the effects of spirometry on bronchial NO flux (J'aw(NO)) and alveolar NO (CA(NO)), two measurements increasingly being used in clinical and research protocols, are unknown. The aim of this study was to evaluate the effect of spirometry on FE(NO), J'aw(NO), and CA(NO) in adults with asthma.
Methods: Forty-four adults with asthma were studied. To assess the impact of exhaled NO measurement itself on exhaled NO values, FE(NO), J'aw(NO), and CA(NO) were obtained twice, at baseline and after a resting period of 10 min. Then spirometry (with or without bronchodilator) was performed followed by exhaled NO measurements at 10 min.
Results: In the group with pre-bronchodilator study only (n = 26), mean (95% CI) values before spirometry were 37.3 ppb (22.2-52.4) for FE(NO), 2375 pl/s (1613-3137) for J'aw(NO), and 1.65 ppb (0.95-2.35) for CA(NO), compared with 35.5 ppb (21.1-49.0, p = .10), 2402 pl/s (1663-3141, p = .85), and 1.60 ppb (0.64-2.56, p = .87) after spirometry, respectively. Spirometry-induced changes in exhaled NO values were also not significant in the group with both pre- and post-bronchodilators (n = 18). Furthermore, changes in FE(NO), J'aw(NO), and CA(NO) values were similar in the two groups.
Conclusions: Our findings demonstrate that spirometry (with or without bronchodilator) does not induce significant changes in bronchial NO flux or alveolar NO values. Therefore, exhaled NO values may be obtained after spirometric maneuvers.