Determinants of the Severity of Exercise-Induced Bronchoconstriction in Patients with Asthma

Aim. In examining the mechanisms of exercise-induced bronchoconstriction (EIB), it is important to determine which factors most strongly affect the severity of EIB. We determined such factors in patients with asthma by stepwise multiple-regression analysis. Methods. Twenty-three patients with asthma underwent pulmonary function tests, methacholine provocation test, and sputum induction. Eosinophilic inflammatory indices and airway vascular permeability index (ratio of albumin concentrations in induced sputum and serum) were examined in sputum samples, and then an exercise test was performed by all asthmatics. Results. There was a significant correlation between the severity of EIB and degree of eosinophilic inflammation in induced sputum. Moreover, there was a significant correlation between the severity of EIB and airway vascular permeability index. Although we could not find a significant correlation between the severity of EIB and 1-sec forced expired volume, 20% provocation concentration of (PC₂₀) methacholine tended to be correlated with the severity of EIB. By stepwise multiple-regression analysis, we also found that airway vascular permeability index, eosinophil cationic protein levels in sputum, and PC₂₀ methacholine are independent predictors of the severity of EIB. Conclusion. We found that airway vascular hyperpermeability, eosinophilic inflammation, and bronchial hyperreactivity are independent factors predicting the severity of EIB.