Bronchial responsiveness to inhaled histamine and exercise

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.