Background: Fraction of exhaled nitric oxide (FeNO) is considered, by some authors, to be a treatment follow-up parameter in allergic asthmatics. However, factors such as active smoking can influence NO production and must be taken into account in the interpretation of FeNO values. In children, the evidence in favour of an impact of passive smoking (PS) on FeNO values is controversial. The aim of this study was to evaluate the impact of chronic PS on FeNO in allergic asthmatic children.
Methods: Seventy nontreated allergic asthmatic children over 5 years of age, exposed and unexposed to PS, underwent measurement of FeNO, spirometry, and allergic tests (skin prick tests, total and specific serum IgE, and blood eosinophilia). Children were considered to be exposed to PS when at least 1 cigarette per day was declared to be smoked at home.
Results: Geometric mean FeNO value in 22 children exposed to PS was 26.3 +/- 1.5 ppb vs 56.3 +/- 1.7 ppb in 48 children unexposed (P < 0.001). After adjustment for age, blood eosinophilia, allergic sensitizations, total IgE, dust mite sensitization and asthma severity, multivariate analysis showed that PS exposure was negatively associated with FeNO values (P = 0.0001) and was the primary determinant of FeNO variations.
Conclusion: Passive smoking lowers FeNO, and might be a major determinant of FeNO levels in nontreated allergic asthmatic children.