title: Central versus peripheral airway obstruction in bronchial responsiveness due to exercise.
abstract: The change in the site of maximal flow-limitation with time in exercise-induced bronchoconstriction was studied in 16 asthmatic children by repeated measurements of maximal flow-volume curves in air and helium-oxygen (80/20). Bronchoconstriction shortly after exercise is determined by flow-limitation in the more peripheral airways in nearly all of the patients. Bronchoconstriction then fades away, while the site of maximal flow-limitation returns towards the central airways. Both variables have a significant relationship (P less than 0.05), which differs with time and among patients. The degree of protection by the beta-sympathetic agonist is more pronounced (mean 28%) than that of the parasympatholytic (mean 3%), and its action increases along with the degree of shift in the maximal flow-limitation towards the periphery. The implications for the mechanism involved and the therapy are discussed.
mesh_terms: D000293:Adolescent; D000318:Adrenergic beta-Agonists; D001249:Asthma / Q000503:physiopathology*; D001250:Asthma, Exercise-Induced / Q000175:diagnosis / Q000503:physiopathology*; D001980:Bronchi / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D002648:Child; D006371:Helium; D006801:Humans; D008449:Maximal Expiratory Flow-Volume Curves; D010100:Oxygen; D010276:Parasympatholytics; D013997:Time Factors
chemical_list: D000318:Adrenergic beta-Agonists; D010276:Parasympatholytics; D006371:Helium; D010100:Oxygen