BRONCHODILATOR RESPONSE IN 3-6.5 YEARS OLD HEALTHY AND STABLE ASTHMATIC-CHILDREN

Few data are available on the bronchodilator response in preschool chi ldren. This study was set up to study baseline lung function and bronc hodilator responses in healthy and asthmatic children younger than 7 y rs old. In 281 preschool children attending kindergarten (age range 2. 7-6.6 yrs old) respiratory system resistance (Rrs) and reactance (Xrs) by impulse oscillation system at 5, 10, 15, 20, 25 and 35 Hz as well as resonance frequency (f(0)) were measured before and 20 min after 20 0 mu g inhaled salbutamol by a metered-dose inhaler connected to a spa cer device. Thirty-four of them were diagnosed as asthmatics based on a validated standardized questionnaire. The mean Rrs (+/-SD) at 5 Hz ( Rrs,5) was 1.03 (+/-0.24) kPa.L-1.s for healthy children and 1.09 (+/- 0.26) kPa.L-1.s for stable asthmatics. The mean change in Rrs,5 after salbutamol was -0.13 (+/-0.20) kPa.L-1.s for the healthy children and -0.09 (+/-0.25) kPa.L-1.s for the asthmatic group. The scatter for the measurements was striking. Neither baseline values of impulse oscilla tion nor its changes after bronchodilator administration was significa ntly different between healthy and stable asthmatic children. A change in respiratory system resistance at 5 Hz of 40% is to be considered t he cut-off for a ''positive'' bronchodilator response.