Childhood asthma: Quantification of the bronchodilator response by impulse oscillometry system

Abstract

Rationale Asthma is common among young children who rarely perform feasible forced expiratory maneuvers. The assessment of respiratory resistance by impulse oscillometry system (IOS), based on the superimposition of respiratory flows by short-time impulses, requires no patient active collaboration. We evaluated the baseline repeatability and bronchodilator response of IOS indices, and their correlation with FEV1 and sRaw. Differences between atopic and non-atopic children were evaluated. Methods Thirty-three asthma children (3-6 yrs.) underwent IOS measurements (R5rs, R20rs and X5rs) by triplicate at each, the baseline, after placebo and after salbutamol inhalation. At the baseline and post-salbutamol, spirometry (FEV1) and whole body plethysmography (sRaw) were performed. Baseline within-test (Coefficient of variation: CV%) and between test (baseline-placebo) repeatability were addressed. The SD index (change in multiples of the between-test repeatability) was used to evaluate the bronchodilator response. Results Baseline repeatability of IOS was 4.1% for R5rs, 4.0% for R20rs and 5.6% for X5rs. R5rs decreased by 2SD after salbutamol and correlated with FEV1 and sRaw at both, baseline (R=-0.51 and R=0.49) and post-salbutamol (r=−0.63 and R=0.54). A trend towards correlation between salbutamol-induced changes in R5rs and in sRaw (r=0.33) was observed. No difference between atopic and non-atopic children was detected. Conclusion IOS was well accepted by young asthma children and provided reproducible and sensitive indices of lung function. Resistance at low frequencies (R5rs) showed the best correlation with plethysmography and spirometry.