Exhaled carbon monoxide levels in preschool-age children with episodic asthma

Background: The concentration of exhaled carbon monoxide (eCO) in young children with stable asthma and during acute asthma attack is not known. Methods: A sampling bag was developed to collect the exhaled air of preschool children. A total of 257 preschool-age children (≥3 years and ≤6 years old) were studied; 111 had a diagnosis of asthma (43 suffering a mild asthma attack and 68 without active asthmatic symptom), 99 had upper respiratory infection (URI) and 47 were healthy. Results: In preschool-age children, eCO levels of those with asthma attacks (mean ± SE, 2.7 ± 0.3 p.p.m., n= 43) were significantly higher than those of subjects with asymptomatic asthma (0.5 ± 0.1 p.p.m., P < 0.05), URI (0.8 ± 0.1 p.p.m., P < 0.05) and healthy children (0.4 ± 0.1 p.p.m., P < 0.05). A multivariate linear regression model showed that eCO was higher in children with asthma attacks independent of age and gender. In 33 asthmatic children followed before and after treatment, eCO levels during asthma attacks significantly decreased after inhalation therapy with a combination of salbutamol and sodium cromoglycate (before therapy, 2.9 ± 0.4 p.p.m.; after therapy, 0.6 ± 0.1 p.p.m., P < 0.0001). Conclusions: The measurement of eCO using a novel collecting system is useful in the recognition of asthma in preschool children.