Smoking effect on exhaled nitric oxide (NO) flow-independent NO exchange parameters

¹ Dept of Medical Cell Biology, Integrative Physiology, Uppsala University, Uppsala, Sweden
² Asthma and Allergy Research Centre, Uppsala University, Uppsala, Sweden; and Dept of Medical Sciences, Respiratory Medicine and Allergology, Uppsala University, Uppsala, Sweden
³ Asthma and Allergy Research Centre, Uppsala University, Uppsala, Sweden; and Dept of Medical Sciences, Occupational and Environmental Medicine, Uppsala University, Uppsala, Sweden
⁴ Dept of Engineering Physics and Mathematics, Helsinki University of Technology, Helsinki, Finland
⁵ Dept of Medical Cell Biology, Integrative Physiology, Uppsala University, Uppsala, Sweden; Asthma and Allergy Research Centre, Uppsala University, Uppsala, Sweden; and Dept of Caring Sciences and Sociology, Section of Medical Science, University of Gävle, Gävle, Sweden

^* To whom correspondence should be addressed. E-mail: Andrei.Malinovschi{at}medcellbiol.uu.se.

	Abstract

It is a well-known fact that smoking is associated with a reduction in exhaled nitric oxide (NO) levels. There is, however, limited knowledge relating to the smoking-induced changes in the production or exchange of NO in different compartments of the airways.

The study comprised 221 adult subjects from the European Community Respiratory Health Survey II who were investigated in terms of their exhaled NO, lung function, IgE sensitisation and smoking habits. The following parameters were determined using the extended NO analysis: Caw_NO (mean airway tissue concentration of NO), Calv_NO (mean alveolar concentration of NO), Daw_NO (airway transfer factor for NO) and FE_{NO 0.05} (fractional exhaled concentration of NO at a flow rate of 50 mL·s^-1). J'aw_NO (total maximum flux of NO in the airways) was calculated by Daw_NOx(Caw_NO-Calv_NO).

Current smokers (n=35) had lower values (geometric mean) of FE_NO0.05 (14.0 vs 22.8 ppb, p<0.001), Caw_NO (79.0 vs 126 ppb, p<0.001) and J'aw_NO (688 vs 1153 pL·s^-1, p=0.001) than never-smokers (n=111). Ex-smokers (n=75) were characterised by lower FE_NO0.05 (17.7 vs 22.8 ppb, p=0.02) and J'aw_NO values (858 vs 1153 pL·s^-1, p=0.02) than never-smokers. These relationships were maintained after adjusting for potential confounders (gender, age, height, IgE sensitisation and FEV₁) and, in this analysis, a negative association was found between current smoking and Calv_NO (p=0.004). Snus consumption (n=21) in ex-smokers was associated with an increase in Daw_NO (p=0.04) and a reduction in Caw_NO (p=0.004), after adjusting for potential confounders. Passive smoking was associated with a higher Calv_NO (p=0.008).

Using extended NO analysis, it was possible to attribute the reduction in exhaled NO levels seen in ex- and current smokers to a lower total airway NO flux in ex-smokers and reduced airway and alveolar NO concentrations in current smokers. The association between snus (oral tobacco) use and reduced NO concentrations in the airways and increased NO transfer from the airways warrants further studies.

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