Oscillometric and spirometric bronchodilator response in preschool children with and without asthma

BACKGROUND: Bronchodilator responses (BDR) are routinely used in the diagnosis and management of asthma; however, their acceptability and repeatability have not been evaluated using quality control criteria for preschool children. OBJECTIVES: To compare conventional spirometry with an impulse oscillometry system (IOS) in healthy and asthmatic preschool children. METHODS: Data from 30 asthmatic children and 29 controls (two to six years of age) who underwent IOS and spirometry before and after salbutamol administration were analyzed. RESULTS: Stable asthmatic subjects significantly differed versus controls in their spirometry-assessed BDR (forced expiratory volume in 1 s [FEV1], forced vital capacity and forced expiratory flow at 25% to 75% of forced vital capacity) as well as their IOS-assessed BDR (respiratory resistance at 5 Hz [Rrs(5)], respiratory reactance at 5 Hz and area under the reactance curve). However, comparisons based on the area under the ROC curve for Delta FEV1 %initial versus Delta Rrs(5) % initial were 0.82 (95% CI 0.71 to 0.93) and 0.75 (95% CI 0.62 to 0.87), respectively. Moreover, the sensitivity and specificity for Delta FEV1 >= 9% were 0.53 and 0.93, respectively. Importantly, sensitivity increased to 0.63 when either Delta FEV1 >= 9% or Delta Rrs(5) >= 29% was considered as an additional criterion for the diagnosis of asthma. CONCLUSION: The accuracy of asthma diagnosis in preschool children may be increased by combining spirometry with IOS when measuring BDR.