Elevated concentrations of exhaled hydrogen peroxide in asthmatic patients

Background: Airway inflammation is important in the development and progression of asthma. Activation of inflammatory cells induces a respiratory burst resulting in the production of reactive oxygen species, such as H2O2. The aim of this study was to measure the concentration of H2O2 in exhaled breath condensate and its correlation with airway obstruction, airway hyperresponsiveness, and concentration of eosinophil cationic protein (ECP) in serum in 70 steroid-naive, atopic patients with unstable asthma (20 men; age range, 18 to 62 years) and 17 normal subjects (7 men; age range, 19 to 34 years). Methods: Exhaled H2O2 was measured using a colorimetric assay, and the concentration of ECP in serum was measured using radioimmunoassay. Airway hyperresponsiveness was expressed as the provocative concentration of inhaled histamine causing a 20% fall in FEV1 (PC20). Results: In patients with asthma, the mean H2O2 concentration was significantly elevated compared to values in normal subjects: 0.127 +/- 0.083 mol/L vs 0.024 +/- 0.016 mol/L (p < 0.001). There was a significant correlation among H2O2 concentration, FEV1, PC20, and ECP in serum. Conclusion: We conclude that exhaled H2O2 is significantly elevated in asthmatic patients. This is correlated with disease severity and indirect markers of airway inflammation. Measurement of exhaled H2O2 may be useful to assess airway inflammation and oxidative stress in asthmatic patients.