Abstract
The respiratory impedance reference values for the forced oscillation technique (FOT) pseudorandom signal in Thai and Asian preschool population have not yet been established. The aim of this study was to determine the reference values for respiratory impedance as predicted by height and arm span using FOT and assess the feasibility and variability associated with the use of this technique in Thai preschool children. FOT pseudorandom signal was used to measure respiratory impedance (Zrs), which is composed of respiratory resistance (Rrs) and respiratory reactance (Xrs), in Thai healthy children aged 3–7 years. Feasibility, within-test variability, between-test repeatability, and association between Zrs values at 6, 8, and 10 Hz and independent variables, including age, weight, height, arm span, and gender, were assessed. Regression equations of Rrs and Xrs values were also determined. Of 291 children, FOT was successfully performed in 233 children (80.1%). Within-test variability was 2%–3% for Rrs and 9%–15% for Xrs. Between-test repeatability showed mean difference between the 2 sets of all Rrs and Xrs values to be nearly zero. Height was found to be the best predicting factor for 5 of 6 Rrs and Xrs values (excluding Xrs10) and arm span also has strong predictability and correlation with Rrs and Xrs values. Arm span can, therefore, be used in place of height in patients whose height cannot be measured, such as patients with kyphoscoliosis or neuromuscular diseases. FOT is a feasible and repeatable method for evaluating lung function in preschool-aged Thai children. The reference values for respiratory impedance as predicted by height and arm span using FOT were determined in this study. The results of this study may be useful in the determination of respiratory impedance reference values in preschool children from other Asian populations in the future.
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