title: Changes in functional residual capacity during exercise in patients with exercise-induced asthma.
abstract: Forty-eight patients with a history of exercise-induced asthma were exercised on ambient breathing (T = 18-20 degrees C, relative humidity = 45-55%). There were 19 responders and 29 non-responders according to post-exercise spirometry. During the first minutes of exercise at a workload of 25-50 W, the functional residual capacity (FRC) was measured by a rebreathing technique. There was a significant increase in FRC in responders (p less than 0.025). A loose though significant correlation was found between the rise in FRC during exercise and the fall in forced expiratory volume in one second (FEV1) after exercise (r = -0.429, p less than 0.005). The effects of a sympathomimetic drug were studied in five responders submitted to a second exercise test 4 h after the first one. Spirometry returned to normal but FRC remained high between both tests. During the second test neither spirometry nor FRC changed. The results suggest that different mechanisms may be responsible for changes in FRC and in maximal expiratory flow in exercise-induced broncho constriction.
mesh_terms: D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000503:physiopathology*; D001250:Asthma, Exercise-Induced / Q000503:physiopathology*; D002000:Bronchospirometry; D005260:Female; D005541:Forced Expiratory Volume; D005652:Functional Residual Capacity; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D005082:Physical Exertion; D013726:Terbutaline / Q000494:pharmacology; D014797:Vital Capacity / Q000187:drug effects
chemical_list: D013726:Terbutaline