The effect of passive smoking on exhaled nitric oxide in asthmatic children

To date, some studies suggest that passive smoking (PS) may be an important determinant of FeNO levels in children but sill there is a need of investigations using objective methods of PS exposure. The aim of our study was to examine the effect of PS, measured by urine cotinine levels, on FeNO and lung function (FEV1) in allergic and non-allergic asthmatic children. METHODS: It was a prospective, non-interventional study. 140 children, aged 4-17, newly diagnosed with asthma were recruited into two study groups (exposed group, unexposed group), according to smoking exposure/unexposure based on the questionnaire. There was one study visit. Subjects underwent a medical history (including history of atopy), physical examination, spirometry, FeNO and urinary cotinine measurement. RESULTS: 70 individuals had been exposed to tobacco smoke. The patients exposed to tobacco smoke were characterized by statistically significantly higher urine concentration of cotinine, 10,80 ng/mL, than their counterparts who had not been exposed to tobacco smoke, 1,56 ng/mL (P = 0,019). In the group of individuals unexposed to tobacco smoke the mean value of FeNO was 34,99 ppb, while in the group of patient who had been exposed to tobacco smoke, the corresponding mean value was significantly lower, it amounted to 22,41 ppb (P = 0,001) (Table 1). As regards to FEV1 measurements, there were not any statistically significant differences by study groups unexposed/exposed to tobacco smoke (P = 0,179 and P = 0,074, respectively). FeNO levels (ppb) in the studied patients allergic to cat, grass or trees, exposed to tobacco smoke were significantly lower than in those children unexposed to tobacco smoke. Our results suggest a clinically important issue, that FeNO results should be interpreted in the context of environmental tobacco smoke exposure. Additionally allergy to cat dander, grass or tree may be potential confounding factor, which should be taken into consideration.