Purpose: Computed tomography studies demonstrate thickening of the asthmatic airway wall and its relation to disease severity. We evaluated the effect of inhaled corticosteroid on this phenomenon.
Methods: Cross-sectional images of the right upper lobe apical segmental bronchus were obtained by helical computed tomography in 45 corticosteroid-naïve patients with persistent asthma and 28 healthy controls. Airway wall thickness was measured as airway wall area normalized to body surface area. Computed tomography, pulmonary function, and serum levels of eosinophil cationic protein were examined before and after treatment with beclomethasone (800 microg/d for 12 weeks).
Results: Before treatment, airway wall thickness was greater in asthma patients than in controls (P <0.0001). After treatment, it decreased by 11% (P <0.001) but remained high (P <0.0001 vs. control); the serum level of eosinophil cationic protein decreased, and airflow obstruction was reduced, but not to the level in controls. The decrease in wall thickness was associated with a decrease in the serum level of eosinophil cationic protein (r = 0.39, P = 0.009) and an increase in the forced expiratory volume in 1 second (r = 0.45, P = 0.003) and was inversely related to disease duration at entry (r = -0.38, P = 0.009). Post-treatment wall thickness was related to disease duration (r = 0.45, P = 0.003) and remaining airflow obstruction.
Conclusion: Wall thickening of asthmatic central airways responds partially to inhaled corticosteroid therapy and may reflect an overall reduction in airway inflammation. "Unresponsive components," possibly involving structural changes, may increase in the absence of inhaled corticosteroid treatment, potentially leading to chronic airflow obstruction.