To examine quantitative end-tidal carbon dioxide (ETCO₂) in children with acute exacerbations of asthma. We hypothesize that quantitative ETCO₂ will be lower in children during an acute exacerbation of asthma and will correlate with the severity of the exacerbation. We also hypothesize that ETCO₂ can be successfully performed in all groups in the setting of a pediatric emergency department.

Patients with acute exacerbation of asthma (n = 86) and control subjects without respiratory or metabolic disturbances (n = 88) were prospectively enrolled in a pediatric emergency department. A physical examination, vital signs, and ETCO₂ measurements were performed on arrival and, in the patients with asthma, after each bronchodilator treatment.

ETCO₂ was measured successfully in 97% of enrolled children. After adjusting for respiratory rate, ETCO₂ was significantly lower in patients with acute exacerbation of asthma than in control subjects (P < .001). ETCO₂ measured after the first and after the final bronchodilator treatment were significantly associated with the number of bronchodilator treatments received and with hospital admission (P ≤ .002).

ETCO₂ can be successfully measured in all children and is significantly lower in children with acute exacerbations of asthma compared with healthy control subjects. Quantitative ETCO₂ may be an objective, noninvasive, and effort-independent way to assess the severity of asthma.