Exhaled Carbon Monoxide Levels in Children with Bronchial Asthma

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Abstract
Exhaled carbon monoxide (eCO) has been proposed as a potential marker of oxidative stress in the asthmatic airways. This study was conducted to investigate eCO levels in different asthma groups in children. Exhaled CO was measured electrochemically in 117 asthmatic and 45 non-asthmatic, non-atopic healthy children between the ages of 6 to 16 years. Exhaled CO levels in viral associated wheeze were similar to healthy controls. However, all symptomatic patients with either persistent or seasonal asthma had higher eCO values (mean ± SD) (2.05 ± 0.9 parts per million (ppm) and 2.30 ± 0.8 ppm) as compared to controls (0.94 ± 0.5 ppm, p < 0.001, p < 0.001, respectively), viral associated wheeze (1.19 ± 0.4 ppm, p < 0.001, p < 0.001, respectively), and symptom-free seasonal asthmatics (1.45 ± 0.6 ppm, p < 0.01, p < 0.001, respectively). In symptom-free seasonal asthmatics eCO levels that were measured at the specific pollen season, were higher than the controls (p < 0.001) and the viral associated wheeze (p < 0.01). However, all these groups were symptom-free and clinically stable, and there were no significant differences between the forced expiratory volume in one second values. In atopic persistent asthmatics eCO levels were 1.5-fold higher than non-atopic ones (p = 0.007, Mann-Whitney U). But there were only nine non-atopic persistent asthmatics, while atopics were 27. No correlation was found between forced expiratory volume in 1 sec and eCO values measured in all asthma groups regardless of inhaled corticosteroid therapy. In conclusion, the measurements of CO in exhaled air may be useful in the evaluation of children with asthma in clinical setting.