Hydrogen peroxide in exhaled air is increased in stable asthmatic children

Exhaled air condensate provides a noninvasive means of obtaining samples from the lower respiratory tract. Hydrogen peroxide (H2O2) in exhaled air has been proposed as a marker of airway inflammation. We hypothesized that in stable asthmatic children the H2O2 concentration in exhaled air condensate may be elevated as a result of airway inflammation. In a cross-sectional study, 66 allergic asthmatic children (of whom, 41 were treated with inhaled steroids) and 21 healthy controls exhaled through a cold trap. The resulting condensate was examined fluorimetrically for the presence of H2O2. All subjects were clinically stable, nonsmokers, without infection. The median H2O2 level in the exhaled air condensate of the asthmatic patients was significantly higher than in healthy controls (0.60 and 0.15 micromol, respectively; p<0.05), largely because of high values in the stable asthmatic children who did not use anti-inflammatory treatment (0.8 micromol; p<0.01 compared to controls). We conclude that hydrogen peroxide is elevated in exhaled air condensate of children with stable asthma, and may reflect airway inflammation

Flow-dependency of exhaled nitric oxide in children with asthma and cystic fibrosis

The concentration of nitric oxide in exhaled air, a marker of airway inflammation, depends critically on the flow of exhalation. Therefore, the aim of this study was to determine the effect of varying the flow on end-expiratory NO concentration and NO output in children with asthma or cystic fibrosis (CF) and in healthy children. Nineteen children with stable asthma, 10 with CF, and 20 healthy children exhaled from TLC while controlling expiratory flow by means of a biofeedback signal at approximately 2, 5, 10 and 20% of their vital capacity per second. NO was measured in exhaled air with a chemiluminescence analyser. Comparisons between the three groups were made by analysing the NO concentration at the endexpiratory plateau and by calculating NO output at different flows. Exhaled NO decreased with increasing flow in all children. Children with asthma had significantly higher NO concentrations than healthy children, but only at the lowest flows. Asthmatics using inhaled steroids (n=13) tended to have lower median exhaled NO than those without steroids. The slope of linearized (log-log transformed) NO/flow plots was significantly steeper in asthmatics than in healthy controls. CF patients had a significantly lower NO concentration and output over the entire flow range studied, compared to asthmatic and control subjects, with a similar NO/flow slope as control subjects. In conclusion, the nitric oxide concentration in exhaled air is highly flow-dependent, and the nitric oxide-flow relationship differs between asthmatics versus cystic fibrosis patients and control subjects. Assessment of the nitric oxide/flow relationship may help in separating asthmatics from normal children

Hydrogen peroxide in exhaled air of healthy children: reference values

An increased content of hydrogen peroxide (H2O2), a marker of inflammation, has been described in the condensate of exhaled air from adults and children with inflammatory lung disorders, including asthma. However, the normal range of [H2O2] in the exhaled air condensate from healthy children has not been established. Therefore, the aim of this study was to determine the reference range of exhaled [H2O2] in healthy school-aged children. Ninety-three healthy nonsmoking children (48 female and 45 male, mean age 10 yrs, range 8-13 yrs), with a negative history for allergy, eczema or respiratory disease and with a normal lung function, participated. Exhaled air condensate was examined fluorimetrically for the presence of H2O2. In addition, the reproducibility of [H2O2] within subjects and between days and the stability of [H2O2] during storage at -20 degrees C were assessed. The median [H2O2] in the exhaled air condensate of all children was 0.13 microM, with a 2.5-97.5% reference range of <0.01-0.48 microM. No significant difference existed between males and females. There was no correlation between exhaled [H2O2] and age or lung function. Repeated [H2O2] measurements on 2 consecutive days showed satisfactory within-subject reproducibility and [H2O2] in stored samples remained stable for at least 1 month at -20 degrees C. In conclusion, this study provides reference data for exhaled hydrogen peroxide in a large group of healthy children. The observed levels were lower than those reported previously for healthy adults and were independent of age, sex and lung function