The study of bronchial hyperresponsiveness in asthmatic children by forced oscillation technique.

We have studied the bronchial hyperresponsiveness (BHR) of children with normal controls and asthma by methacholine inhalation challenge, using a forced oscillation method. Four parameters, respiratory conductance (Grs), bronchial responsiveness (PD35Grs), bronchial sensitivity (Dmin) and reactivity (SGrs) were studied. There were three patterns of dose-response curves identified in this study, which were significantly correlated to the clinical severity of asthma. (r = 0.846, p less than 0.001, Spearman's rank correlation). There were significant negative correlations between control Rrs (Rrs cont.) and age (r = 0.514, p less than 0.001) or body height (r = 0.685, p less than 0.001). Positive correlations between SGrs and subjects' age (r = 0.457, p less than 0.001) and body height (r = 0.496, p less than 0.001) were also noted. In the normal controls, Dmin and PD35Grs were over 25 units and 50 units, respectively. The Grs for normal children was statistically higher than that of asthmatic children (p less than 0.05). In the asthmatic children, there were significant differences among all subgroups in PD35Grs (p less than 0.001) and Dmin (p less than 0.01). In summary, the bronchial provocation test using the forced oscillation technique is simple, fast and easy to be applied to children. In addition to being capable of investigating BHR, it may offer valuable information for the clinical diagnosis and treatment of asthmatic children.