The Role of Exhaled Nitric Oxide in Evaluation of Acute Asthma in a Pediatric Emergency Department

Objectives: Fractional excretion of nitric oxide (FENO) has been used as a noninvasive marker to assess and manage chronic asthma in adults and children. The aim of this study was to determine the feasibility of obtaining FENO concentrations in children treated in the emergency department (ED) for acute asthma exacerbation and to examine the association between FENO concentrations and other measures of acute asthma severity. Methods: This was a cross‐sectional study of a convenience sample of children 2–18 years old who were seen in an urban ED for acute asthma exacerbation. Using a tidal breathing method with real‐time display, the authors measured FENO concentrations before and 1 hour after the administration of corticosteroids and at discharge from the ED. Outcome measures included pulmonary index score (PIS), hospital admission, and short‐term outcomes (e.g., missed days of school). Results: A total of 133 subjects were enrolled. Sixty‐eight percent (95% confidence interval [CI] = 60% to 76%) of the subjects provided adequate breaths for FENO measurement. There was no difference in the median initial FENO concentration among subjects, regardless of the severity of their acute asthma. Most subjects showed no change in their FENO concentrations from the start to the end of treatment. FENO concentrations were not significantly associated with other short‐term outcomes. Conclusions: Measurement of FENO is difficult for a large proportion of children with acute asthma exacerbation. FENO concentration during an asthma exacerbation does not correlate with other measures of acute severity and has limited utility in the ED management of acute asthma in children.