Impulse oscillometry and free-running tests for diagnosing asthma and monitoring lung function in young children.

BACKGROUND Separating viral-induced wheezers from asthmatics is challenging, and there are no guidelines for children under 6 years of age. Impulse oscillometry is feasible beginning 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. METHODS Forty-two children (median age 5.3 years, range 4.0-7.9 years) with doctor diagnosed asthma and lability in oscillometry were followed for 6 months after initiation of inhaled corticosteroid treatment. All children performed the 6-minute free-running test and impulse oscillometry at three time points. After the baseline, they attended a second visit when they had achieved good asthma control, and a third visit about 60 days after the second visit. A positive ICS-response was defined as having greater than 19 points in ACT and no hyperreactivity on the third visit. RESULTS In total, 38/42 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 (800m vs. 850m vs. 850m, p= .001). Significant improvements in childhood asthma control (C-ACT) scores occurred between the baseline and subsequent visits (21 vs. 24 vs. 24, p < .001) and acute doctors' 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.