Background: 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.

Background and Aim The eucapnic voluntary hyperventilation (EVH) testing is a diagnostic tool for diagnostics of exercise‐induced bronchoconstriction; while the testing has become more common among children, data on the test's feasibility among children remain limited. Our aim was to investigate EVH testing feasibility among children, diagnostic testing cut‐off values, and which factors affect testing outcomes. Methods We recruited 134 patients aged 10–16 years with a history of exercise‐induced dyspnoea and 100 healthy control children to undergo 6‐min EVH testing. Testing feasibility was assessed by the children's ability to achieve ≥70% of the target minute ventilation of 30 times forced expiratory volume in 1 s (FEV1). Bronchoconstriction was assessed as a minimum of 8%, 10%, 12%, 15% or 20% fall in FEV1. Patient characteristics were correlated with EVH outcomes. Results Overall, 98% of the children reached ≥70%, 88% reached ≥80%, 79% reached ≥90% and 62% reached ≥100% of target ventilation in EVH testing; of children with a history of exercise‐induced dyspnoea, the decline percentages were as follows: 24% (≥8% fall), 17% (≥10% fall), 10% (≥12% fall), 6% (≥15% fall) and 5% (≥20% fall) in FEV1, compared to 11%, 4%, 3%, 1% and 0% among the healthy controls, respectively. Healthy controls and boys performed testing at higher ventilation rates ( p < .05). Conclusion Eucapnic voluntary hyperventilation testing is feasible among children aged 10–16 years and has diagnostic value in evaluating exercise‐induced dyspnoea among children. A minimum 10% fall in FEV1 is a good diagnostic cut‐off value. Disease status appears to be important covariates.

The EVH test was successful in the 10-16-year-old children having participated in the study and the test was well tolerated. Through the study, it was possible to provoke both dysfunctional breathing disorder and bronchoconstriction in the symptomatic patients. Based on the pilot study, EVH test seems to be usable in the diagnostics of pediatric exercise-induced dyspnea but larger studies are warranted to confirm our preliminary findings.