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 (beta = -0.52, p = 0.02) and body weight (beta = -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.
