Respiratory impedance and bronchodilator response in healthy Italian preschool children

Objective To define normal values for respiratory resistance (R(rs)) and reactance (X(rs)) and bronchodilator response (BDR) in a population of healthy Italian preschool children using a commercially available forced oscillation device Methods R(rs) and X(rs) 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 mu g of inhaled salbutamol and calculated as an absolute change in R(rs) and X(rs) 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) R(rs) and X(rs) at 6 8 and 10 Hz were related to height but not other variables The CR was 1 53 hPa s L(-1) for R(rs8) and 091 hPa s L(-1) for X(rs8) The 5th percentile for absolute R(rs8) BDR was -3 16 hPa s L(-1) whereas the 95th percentile for absolute X(rs8) 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 R(rs) and X(rs) in healthy Italian preschool children using forced oscillations We recommend a change in Z score of -1 88 for R(rs8) and 2 48 for X(rs8) as cut off values for a positive BDR Pediatr Pulmonol 2010, 45 1086-1094 (C) 2010 Wiley Liss Inc