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Updated: Feb 13, 2026
Conducting Respiratory Oscillometry in an Outpatient Setting
Published on: April 8, 2022
Early detection of airway obstruction by impulse oscillometry system in methacholine challenge testing in preschool
Jung Won Yoon1, Youn Ho Sheen2, Eun Kyo Ha3
1Department of Pediatrics, Myongji Hospital, Seonam University College of Medicine, Goyang, Republic of Korea.
Insights
In preschool children with asthma, reactance at 5 Hz (Xrs5) is a better predictor of bronchial hyperresponsiveness than clinical signs alone. This finding aids in early asthma detection and management.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Asthma Research
Background:
- Small airway hyperresponsiveness is key in pediatric asthma control.
- Assessing bronchial hyperresponsiveness in preschoolers is crucial for asthma management.
- Impulse Oscillometry (IOS) measures lung function parameters like reactance (Xrs) and resistance (Rrs).
Purpose of the Study:
- To explore the relationship between IOS parameters (Xrs, Rrs), FEV1, and clinical indicators in children with asthma symptoms.
- To identify which IOS parameter best predicts bronchial hyperresponsiveness before clinical endpoints are met.
Main Methods:
- A methacholine challenge test was conducted on 94 preschool children suspected of having asthma.
- The study defined the end of the test (EOT+) by audible wheezing (PCw+), decreased oxygen saturation (PCs+), or respiratory symptoms (PCr+).
Main Results:
- Changes in FEV1, Xrs5, and Rrs5 were significant at EOT+.
- Xrs5 changes exceeded 80% in all EOT+ groups and correlated better with oxygen saturation changes (r=-0.578) than Rrs5 (r=-0.426).
- A 49% decrease in Xrs5 was identified as an optimal predictor for subsequent significant changes.
Conclusions:
- Clinical parameters alone are insufficient as endpoints in methacholine challenge tests for preschoolers.
- Reactance at 5 Hz (Xrs5) is a valuable predictive marker for bronchial hyperresponsiveness in this age group.
- IOS, specifically Xrs5, offers a sensitive measure for assessing airway reactivity in young children with asthma.
Background:
Small airway hyperresponsiveness is a critical aspect in preschool children with asthmatic symptoms interms of asthma control. The aim of this study was to elucidate the relationship of changes in reactance (Xrs) and resistance (Rrs) of IOS and FEV1 with those in clinical parameters and to determine which IOS parameter is correlated with bronchial hyperresponsiveness before positive clinical endpoints.
Methods:
We performed the methacholine challenge test in ninety-four preschool children (4.2±1.1 years) with suspected asthma. The end of test (EOT+) was defined as one or more of the following: audible wheezing (PCw+), a fall in the oxygen saturation (w92%, PCs+) or development of respiratory symptoms (PCr+).
Results:
Mean changes in FEV1, Xrs5, and Rrs5 in the EOT+ group were 39.2±14.3% (95% CI 35.1-43.2%), 176.8±78.0 (95% CI 154.9-198.8) and 53.6±30.2 (45.1-62.0), respectively. The changes of Xrs5 in three EOT+ groups exceeded 80% and were lowest in PCr+(median, 95.9, IQR;73.4 to 132.4), followed by PCw+ and PCs+. However, Rrs5 did not show greater than 40% changes in PCr+. Xrs5 showed a higher correlation with changes in saturation (r=-0.578) than Rrs5 (r=-0.426). A49% decrease in Xrs5 was the optimal point for predicting a 80% change of Xrs5 at the following step.
Conclusion:
When examining the 5 step methacholine challenge test in preschoolers, the use of clinical parameters alone as an endpoint is of little value. The reactance value of 5 Hz is a useful predictive marker for bronchial hyperresponsiveness.
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