Relation of airway reactivity and sensitivity with bronchial pathology in asthma

Airway hyperresponsiveness in asthmatics, which may result from inflammation or remodeling, is expressed as the concentration of methacholine that causes a 20% fall in FEV₁ in the concentration-response curve (PC₂₀). A decrease in PC₂₀ may be due to a steeper curve (hyperreactivity) and/or a curve shift to the left (hypersensitivity). Our purpose was to analyze the relation of airway sensitivity and reactivity to airway pathological changes. The PC₆, as sensitivity parameter, and the slope between PC₂₀ and PC₄₀ as reactivity parameter, were calculated. Total and differential cell counts in the bronchoalveolar lavage fluid, and percentage of epithelial shedding, basement membrane thickness, and submucosal thickness on bronchial biopsy, were measured. The PC₆ showed a correlation with the baseline FEV₁%. The slope was significantly correlated with the basement membrane thickness, and also demonstrated a strong association with submucosal thickness. The PC₂₀ showed a correlation with the baseline FEV₁% and the degree of epithelial shedding. These results suggest that the airway sensitivity and reactivity measurements reflect the degree of airway caliber and remodeling, respectively.