Carbon monoxide (CO) can be detected in exhaled air and is increased in adult and childhood persistent asthmatic patients. However, little is known about the exhaled CO concentration in episodic childhood asthma. This study aimed to clarify whether measurement of exhaled CO is useful in monitoring disease activity in children with episodic asthma. We measured exhaled CO concentration by modified Micro-Smokerlyzer in 217 elementary school children (132 boys; mean age, 10 +/- 1 (SE) years; range, 9-12 years), in whom 29 had infrequent episodic asthma without current exacerbations. We also measured exhaled CO concentrations in 22 children with episodic asthma (13 boys; mean age, 10 +/- 3 years; range, 8-12 years), who had acute mild asthmatic attacks during examination. In these patients with mild asthmatic attacks, exhaled CO was measured both before and after combination therapy with salbutamol and sodium cromoglycate (SCG) by powered nebulizer. Among 217 schoolchildren, exhaled CO levels in infrequent episodic asthmatic children (1.1 +/- 0.1 parts per million (ppm), n = 29) were not significantly different from those in healthy schoolchildren (1.0 +/- 0.1 ppm, n = 188, P > 0.68). The exhaled CO concentrations during asthma attacks in children with episodic asthma were significantly higher (5.1 +/- 0.4 ppm, n = 22) compared with those in healthy children (P < 0.001) or those in asymptomatic asthmatic children (P < 0.001). The elevated exhaled CO levels were significantly decreased after inhalation therapy of a combination of salbutamol and SCG (3.2 +/- 0.5 ppm, n = 22, P < 0.02). In conclusion, exhaled CO levels were significantly elevated during acute asthma exacerbations, and partially recovered after treatment with beta(2)-agonist and SCG in children with mild episodic asthma. These findings indicate that measurement of exhaled CO might provide another noninvasive measurement of asthma exacerbations that would be suitable for use in children with acute mild episodic asthma.
The measurement of eCO using a novel collecting system is useful in the recognition of asthma in preschool children.
Objective: There are few lung function tests available to evaluate bronchial asthma in infants and toddlers. The objective of this study was to test the hypothesis that the measurement of exhaled carbon monoxide (eCO) levels is applicable to evaluate infants and toddlers with stable asthma and during acute asthma attack. Methods: A one-way valve breath sampling bag was developed to collect the exhaled air of infants and toddlers. A total of 483 infants (under 2 years) and toddlers (2-5 years) were studied; 355 had an established diagnosis of asthma (182 suffering mild asthma attacks and 173 without active asthmatic symptoms), 119 had upper respiratory infection (URI) including acute bronchitis, and 9 were healthy. Results: In infants and toddlers, eCO levels of those with asthma attacks [median (interquartile range) = 2.0 (2.0-3.25) ppm, n =182] were significantly higher than those of subjects with asymptomatic asthma [2.0 (1.0-2.0) ppm, n =173, P < 0.0001], URI [2.0 (1.0-3.0) ppm, n =119, P < 0.0001], and healthy children [1.0 (0.0-1.0) ppm, n =9, P < 0.0001]. In 75 children with asthma petit mal, eCO levels during asthma attacks [3.0 (2.0-4.0) ppm] significantly decreased after therapy [1.0 (1.0-2.0) ppm, P < 0.0001]. In infants and toddlers with an established diagnosis of asthma ( n =355), eCO cut-off >2 ppm discriminated asthma attack from an asymptomatic state with a sensitivity of 95.6%, a specificity of 43.3%, and an area under the curve (AUC) of 0.71 (95% CI: 0.65-0.76, P < 0.0001). In 401 infants and toddlers with some respiratory symptoms, of which 285 cases were finally diagnosed as asthma [eCO level = 2.0 (2.0-3.0) ppm] and 116 cases were not asthma [eCO level = 2.0 (1.0-3.0) ppm, P < 0.0001], eCO cut-off >3 ppm supported the final diagnosis of asthma with a sensitivity of 38.9%, a specificity of 74.1%, and AUC of 0.63 (95% CI: 0.56-0.69, P < 0.0001). Conclusion: The measurement of eCO by a novel method is applicable to evaluate asthmatic activity and treatment responsiveness, and to diagnose asthma in infants and toddlers.
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