Airway closing index in school-age children during exercise bronchoprovocation

Abstract

Objective

Airway Closing Index (ACI), the ratio of % change in FVC to % change in FEV₁ with bronchoprovocation, may represent changes in airflow due to airway closure, as opposed to airway narrowing. The objective of this study was to evaluate ACI during exercise bronchoprovocation (EB) in children.

Methods

Children, 6 to 18 years of age, who underwent EB using a stationary bicycle ergometer over a 6-year period were reviewed. Pulmonary function, including ACI, in patients with a positive exercise challenge, defined as ≥10% decrease in FEV₁ following exercise, were compared to patients with a negative challenge.

Results

A total of 1030 children with a median age of 13 (IQR 11–15) underwent EB, of which 376 (37%) had a positive exercise challenge. There was wide variability in ACI, with a median of 0.75 (0.28–1.21). Median ACI in those with a positive test was 0.68 (IQR 0.41–0.93) compared to 0.84 (IQR 0.09–1.06) for those with a negative test, p = 0.017. Median ACI was higher in older children (p < 0.001) and females (p < 0.0001). Median percent change in FEV₁ following bronchodilator for children in the highest quintile for ACI was 4.5 (IQR 1.3–8.1) compared to 5.5 (IQR 2–9.2) for children in the lowest quintile, p = 0.04.

Conclusions

There is wide variability in the ACI in children undergoing EB. ACI was lower in children with a positive challenge, the significance is unknown. Children with higher ACI may have increased airway closure with bronchoprovocation, and less response to bronchodilators.

KEYWORDS:

• Airway closure
• exercise-induced bronchospasm
• lung function
• obesity
• bronchodilator

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.