Passive smoking and expired carbon monoxide concentrations in healthy and asthmatic children.

BACKGROUND Carbon monoxide (CO) in expired air has been reported to be an indirect measurement for the quantity of passive smoking. Since endogen CO is produced in inflammatory processes and inflammation is the main pathogenetic mechanism of asthma, it was aimed to investigate the relationship between the intensity of passive smoking and CO concentration in expired air of healthy and asthmatic children. METHODS AND RESULTS The study was performed in the outpatient pediatrics clinics and day care centers. Knowledge about indoor smoking habits were obtained from parents. The exhaled CO concentrations were measured by a portable device in 235 healthy (mean age, 4.4 +/- 2.3 years) and 54 asthmatic (mean age, 4.5 +/- 1.7 years) children. Children with no smoking parents had the lowest exhaled CO concentrations. Significant relationships were found between the number of smoking cigarettes in the house and exhaled CO concentrations in both healthy (p = 0.003) and asthmatic (p = 0.01) children. Carbon monoxide concentrations were higher in asthmatic children than healthy ones (mean +/- SD, 1.32 +/- 1.50 ppm and 0.86 +/- 1.35 ppm, respectively, p = 0.028) if their parental smoking habits were not taken into account. Asthmatic children of non-smoking parents had higher CO concentrations than healthy subjects of non-smoking parents (1.05 +/- 1.55 ppm vs 0.37 +/- 0.53 ppm, p = 0.01). On the other hand, asthmatic children who has no smoking parents and did not receive inhaled steroids had significantly higher CO concentrations (1.75 +/- 1.45 ppm) than those who received steroids (0.58 +/- 0.65 ppm, p = 0.024). CONCLUSIONS Exhaled CO can be used as an indicator of passive smoking in children. Higher expired CO of asthmatic children may reflect inflammation of the lung in asthma.