Inflammatory Markers and Acid-Base Equilibrium in Exhaled Breath Condensate of Stable and Unstable Asthma Patients

Abstract

Background: Nitrosative and acid stress play an important role in the pathogenesis of asthma. The aim of this study was to evaluate whether, in asthmatics, a link exists between the concentrations of nitrite/nitrate, ammonia and pH values in exhaled breath condensate (EBC) and asthma severity, lung function, exhaled nitric oxide (F_ENO), total IgE, eosinophil cationic protein (ECP) and blood eosinophilia. Methods: The above-mentioned parameters were measured in 19 healthy volunteers and 91 allergic asthmatics divided into three groups, i.e. 22 subjects with steroid-naïve stable asthma, 35 with inhaled corticosteroid (ICS)-treated stable asthma and 34 with ICS-treated unstable asthma. Results: Compared with healthy subjects, EBC from asthmatics had significantly lower pH values and ammonia concentrations and significantly higher levels of nitrite/nitrate. The extent of these changes was higher in patients with unstable than in patients with steroid-naïve and stable ICS-treated asthma. The EBC pH was positively correlated with ammonia and negatively correlated with nitrite/nitrate, F_ENO or blood eosinophilia in all three groups of asthmatics. Significant positive correlations between EBC nitrite/nitrate and blood eosinophilia, ECP levels or F_ENO were observed in all groups of asthmatics. Significant negative correlations between EBC ammonia and nitrite/nitrate, F_ENO, ECP concentrations or blood eosinophilia were demonstrated in the groups of ICS-naïve and ICS-treated stable asthmatics. Conclusions: In asthmatic patients there is a relationship between EBC pH, ammonia and nitrite/nitrate concentrations and other recognized markers of airway inflammation. EBC pH values, ammonia and nitrite/nitrate levels measured together may help to assess airway inflammatory status and asthma severity.