Measurement of airway resistance using the interrupter technique in preschool children in the ambulatory setting

This study describes the feasibility, repeatability, and interrater reliabi lity of the measurement of airway resistance by the interrupter technique ( Rint) in children 2-5 yrs of age, and examines whether reversibility to bro nchodilator can be demonstrated in wheezy children. The mean of six Rint values was taken as a measurement. If subjects could c omplete one measurement and then a second 15 min after bronchodilator, base line testing and reversibility testing were considered feasible. To measure repeatability, two measurements 30 s apart and measurements before and 15 min after placebo bronchodilator were compared. Measurements by two testers were compared for interrater reliability. Change in Rint in wheezy childre n was measured after bronchodilator. Fifty-six per cent of 2-3-yr-olds (n=79), 81% of 3-4-yr-olds (n=104) and 95 % of 4-5-yr-olds (n=88) completed baseline testing, and 53%, 71% and 91% co mpleted reversibility testing. Baseline measurements were 0.47-2.56 kPa.L-1 .s. Repeatabilities (2 SD of the mean differences between measurements) at 30 s in the three age bands were 0.21, 0.17 and 0.15 kPa.L-1.s and 0.19 kPa .L-1.s after placebo. Using 0.21 kPa.L-1.s as the threshold for reversibili ty, reversibility was demonstrated in most wheezy children. Interrater reli ability was 0.15 kPa.L-1.s. Preschool children can undertake measurements of airway resistance by the i nterrupter technique in ambulatory settings and reversibility to bronchodil ator in wheezy children can be demonstrated. This technique promises to be a useful clinical and research tool.