Respiratory impedance and bronchodilator response in healthy Italian preschool children

Objective To define normal values for respiratory resistance (Rrs) and reactance (Xrs) and bronchodilator response (BDR) in a population of healthy Italian preschool children using a commercially available forced oscillation device. Methods Rrs and Xrs were measured in kindergartens in Viterbo, Italy. Regression analysis was performed taking into account height, weight, age, gender, and reference equations calculated. The coefficient of repeatability (CR) between two tests performed 15 min apart was calculated in a subset of children. BDR was assessed by repeating the measurements 15 min after the administration of 200 µg of inhaled salbutamol and calculated as an absolute change in Rrs and Xrs at 8 Hz, as a percent change in baseline, and as a change in Z‐score calculated from the reference equations. Results Lung function was attempted in 175 healthy children and successful in 163 (81 male, median age 4.8, range 2.9–6.1 years). Rrs and Xrs at 6, 8, and 10 Hz were related to height but not other variables. The CR was 1.53 hPa s L−1 for Rrs8 and 0.91 hPa s L−1 for Xrs8. The 5th percentile for absolute Rrs8 BDR was −3.16 hPa s L−1, whereas the 95th percentile for absolute Xrs8 BDR was 2.25 hPa s L−1. These cut‐off values corresponded to a change in the Z‐score of −1.88 and 2.48, respectively. Conclusions We have established reference equations for Rrs and Xrs in healthy Italian preschool children using forced oscillations. We recommend a change in Z‐score of −1.88 for Rrs8 and 2.48 for Xrs8 as cut‐off values for a positive BDR. Pediatr Pulmonol. 2010;45:1086–1094. © 2010 Wiley‐Liss, Inc.