Cut-off values for positive bronchodilator response in healthy Thai preschool children using forced oscillation technique.

Abstract

Forced oscillation technique (FOT) requires minimal patient cooperation and is particularly useful in young children. Bronchodilator test is a valuable tool for wheezy and asthmatic patients. The cut-off value for bronchodilator response by FOT in healthy Thai children has not been reported. To determine the cut-off values for positive bronchodilator response in healthy Thai preschool children using pseudorandom FOT. FOT was used to measure respiratory function at baseline and after 400 mcg MDI salbutamol in healthy Thai children aged 3-6 years. Respiratory resistance (Rrs) and reactance (Xrs) at 6, 8, and 10 Hz were collected. Pre- and post-bronchodilator tests were compared using paired t-test. Absolute and percent changes after bronchodilator were calculated and their cut-off values were defined as mean ± 1.96 SD. Correlation between each of those and baseline data was analyzed using Pearson's correlation coefficient. Of the 150 enrolled children, FOT measurement at baseline and after bronchodilator was successfully completed in 111 children (51 boys). The mean ± standard deviation age, height, and arm span was 5.2 ± 1.1 years, 109.3 ± 8.7 cm, and 107.2 ± 9.1 cm, respectively. No correlation was observed between any absolute or percent changes in bronchodilator response and gender, age, height, or arm span. The cut-off values established for bronchodilator response by percent change were, as follows: Rrs6: -23%, Rrs8: -20%, Rrs10: -20%, Xrs6: 36%, Xrs8: 60%, and Xrs10: 43%. The cut-off values identified in this study will be useful for evaluating bronchodilator response by FOT in wheezy and asthmatic young children.