Bronchial responsiveness to histamine after repeated exercise-induced bronchospasm.

摘要: The effects of repeated exercise-induced bronchospasm on nonspecific (nonallergenic) bronchial responsiveness (NSBR) to histamine were studied in 12 asthmatic patients (6 F, 6 M). Baseline NSBR, determined by the provocative concentration giving a 20% fall FEV1 (PC20), ranged from 0.41 10.2 mg/ml (geometric mean ± SD: 2.6 2.5). Each subject performed three consecutive exercises ergometer for min at 70% their VO2 max. test was preceded and followed inhalation (HIT). On control day, 4 HIT done 1 h interval, without intercurrent exercise. A significant reduction observed day first fourth HIT. exercise percent 19.4 12.9, 16.2 12.2 15.8 12.7 after but no difference could be found between four PC20 measurements. Four subjects showed refractoriness second change response during refractory period. In conclusion, (1) do not NSBR; (2) period is due (3) tachyphylaxis occurs some inhalations