Expired Breath Hydrogen Peroxide Is a Marker of Acute Airway Inflammation in Pediatric Patients with Asthma

Airway inflammation is important in the development and progression of many pulmonary disorders, including asthma. We hypothesized that the hydrogen peroxide (H2O2) concentration in expired breath may be a marker of airway inflammation. Expired breath condensate was collected by cooling and the H2O2 concentration was measured fluorimetrically. Thirty-five samples were collected from 22 pediatric patients with asthma who were 7 to 18 yr of age and from 11 healthy, nonasthmatic controls. Asthmatic subjects were determined to be well or sick (acute disease of the upper or lower respiratory tract) by clinical examination. Pulmonary function tests were determined to be abnormal if there was a > 15% reduction in FEV1 or > 20% reduction in FEF25–75 compared with baseline values. Expired breath H2O2 was elevated in asthmatic subjects compared with controls (0.81 ± 0.70 versus 0.25 ± 0.27 µmol/L). The difference was primarily due to elevation of H2O2 in sick asthmatic subjects, whose expired breath H2O2 level of 1...