Summary
Separating individuals with viral-induced wheezing from those with asthma is challenging, and there are no guidelines for children under 6 years of age. Impulse oscillometry, however, is feasible in 4-year-old children.
Objective: To explore the use of impulse oscillometry in diagnosing and monitoring asthma in young children and evaluating treatment response to inhaled corticosteroid (ICS).
Methods: A total of 42 children (median age 5.3 years, range 4.0-7.9 years) with physician-diagnosed asthma and lability in oscillometry were followed for 6 months after initiation of ICS treatment. All children performed the 6-minute free-running test and impulse oscillometry at 3 time points. After the baseline, they attended a second visit when they had achieved good asthma control and a third visit approximately 60 days after the second visit. A positive ICS response was defined as having greater than 19 points in asthma control test and no hyperreactivity on the third visit.
Results: In total, 38 of 42 children responded to ICS treatment. Exercise-induced increases of resistance at 5 Hz decreased after ICS treatment (61% vs 18% vs 13.5%, P < .001), and running distance during the 6-minute test was lengthened (800 m vs 850 m vs 850 m, P = .001). Significant improvements in childhood asthma control scores occurred between the baseline and subsequent visits (21 vs 24 vs 24, P < .001) and acute physicians’ visits for respiratory symptoms (1, (0−6) vs 0, (0−2), P = .001). Similar profiles were observed in children without aeroallergen sensitization and among those under 5 years of age.
Conclusion: Impulse oscillometry is a useful tool in diagnosing asthma and monitoring lung function in young children

Relevance
Impulse oscillometry combined with Free Running Test is a useful tool for identifying asthma in young children. Without objective testing, there is a risk of overdiagnosing and misdiagnosing asthma and overtreating ICS, which is why objective testing is needed.