Forced-oscillometry indices to assess the response to ICS-LABA combination and the improvement of airway inflammation in asthmatic children

<bold>Objectives:</bold> To assess the effect of one-month treatment with ICS-LABA combination on respiratory resistance (Rrs) and reactance (Xrs) in steroid-naive asthmatic children and compare forced oscillation technique (FOT) changes to those of FEV1, FEF75, and fractional exhaled NO (FeNO) values. <bold>Methods:</bold> Twenty-seven children with asthma (mean age 9.61 years, range 4.3-15 years) underwent spirometry, FOT (at 5Hz), and FeNO measurements. We assessed the % change of the above parameters and the changes in bronchodilator response one month after the initiation of therapy and the correlation between FEV1, FEF75, Rrs, Xrs, and FeNO improvement. <bold>Results:</bold> There was an increase in FEV1 (7.6 ± 13%) and FEF75 (19.7 ± 29.5%), and a decrease in Rrs (–9.2 ± 20.9%), Xrs (–16.3 ± 26.9%), and FeNO values (–19 ± 52.6%) one month after the initiation of ICS-LABA combination. There was also a significant improvement in bronchodilator response for FEV1 (11.9 ± 7.2 vs. 4.2 ± 4.1%; p<0.001), FEF75 (44.4 ± 39.5 vs. 24.1 ± 27.4%; p=0.023), and Rrs (–29.5 ± 11.9 vs. –17.9 ± 14.3%; p=0.004), but not for Xrs (–37.4 ± 14.8 vs. –31.1 ± 17.6%; p=0.170). FeNO decrease correlated significantly with Rrs (rho 0.467; p=0.014) and Xrs decrease (0.412; p=0.033), but not with the improvement of FEV1 (–0.182; p=0.364) and FEF75 (–0.205; p=0.304). Rrs decrease could predict FeNO decrease with 90.5% sensitivity and 83.3% specificity. <bold>Conclusion:</bold> FOT parameters Rrs and Xrs may be used to assess the response to ICS-LABA combination and the improvement of airway inflammation in steroid-naive asthmatic children.