Measurements of upper and lower airway nitric oxide in healthy adults

Abstract

Introduction. Nasal nitric oxide (NO) measurement can be a useful tool for monitoring upper airway diseases. However, there is a considerable lack of validation data. Aims. To evaluate the repeatability and intra-subject variations of nasal NO output (nV NO) in healthy adults and to study its correlation with lower airway NO parameters. Methods. nV NO was measured in healthy non-smokers at baseline (N = 31, age: 28 ± 6 years), after 1 h (N = 15), 1 d (N = 15), 1 week (N = 17), and compared using the Bland–Altman method. At baseline, lower airway NO parameters (F ENO, flux of NO in the conducting airways and alveolar NO concentration) were also measured and correlated to nV NO (Spearman correlation). Multivariate regression analysis was used to assess the factors influencing nV NO. Results. Baseline median nV NO was 465 (interquartile range (IQR) = 404–536) nL min−1. The mean differences between the baseline and repeated measurements were not significant (p > 0.05). The coefficient of repeatability (mean: 118, IQR = 88–181 nL min−1) and coefficient of variation (mean: 9.1%) were low. We found no correlation between nV NO and lower airway NO parameters (p > 0.05). Sex (β = −0.52, p = 0.02) and body weight (β = −0.65, p = 0.03) influenced nV NO (model: p = 0.04, R 2 = 0.31). Conclusion. nasal NO output has good repeatability in healthy adults. The NO productions of lower and upper airways are not related in health, but nasal NO output seems to be affected by sex and body weight.