Small Airway Disease in Asymptomatic Asthmatic Adolescents

Abstract To determine the frequency of persistent obstruction of the small airways in adolescents with asthma during asymptomatic periods, frequency dependence of dynamic compliance was measured in 15 adolescents. The subjects, selected from 500 children participating in a long-term epidemiologic study of asthma, had normal respiratory resistance and lung volume. They came from the mild to moderate end of the spectrum of asthma in childhood, because all children in the epidemiologic study with severe asthma had abnormal respiratory function tests. Eight of the 15 adolescents had frequency dependence of dynamic compliance; its presence did not correlate with the number of episodes of overt wheezing or the time lapse from the most recent episode. Frequency dependence of compliance in 5 of the 7 subjects was abolished after an inhalation of isoproterenol. The study indicated that small airway obstruction persisted in some adolescents with mild to moderate asthma during asymptomatic periods, but its presence could not be predicted on the basis of clinical findings. To determine its significance will require a simpler method of detection than measurement of frequency dependence of dynamic compliance.