Original article
Bronchial responsiveness to inhaled histamine and exercise

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Abstract

Bronchial responsiveness to inhaled histamine and exercise was measured in 19 asthmatics. Histamine aerosol was inhaled to determine the provocative concentration producing a 20% fall in forced expired volume in one second (FEV1) (PC20). Exercise was performed on a treadmill and a cycle ergometer; following each procedure the percent fall in the FEV1 (ΔFEV1) and the exercise lability (percent rise in FEV1 plus percent fall in FEV1) were calculated. ΔFEV1 and exercise lability after both forms of exercise were similar. PC20 correlated with ΔFEV1 and exercise lability in both forms of exercise; however, the correlation with exercise lability was better. PC20 was more sensitive in demonstrating bronchial hyperresponsiveness. The close correlation between the level of bronchial responsiveness to histamine and exercise supports the view that release of endogenous chemical mediators is an important determinant of exercise-induced asthma. The treadmill exercise and cycle ergometry protocols were equally effective in producing exercise-induced asthma.

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Supported by Grant No. MA5888 from the Medical Research Council of Canada.

Fellow in Respirology and Allergy supported by Bencard Allergy Service, Weston, Ontario.

∗∗

Fellow of the Medical Research Council of Canada; current address: Division of Pulmonary Medicine, University of Saskatchewan, Saskatoon.

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