Characterizing eosinophilic airway inflammation in chronic obstructive pulmonary disease: clinical, functional and bronchoscopic analysis

Abstract

Background
Chronic obstructive pulmonary disease (COPD) shows marked variability in airway inflammatory patterns. Despite this heterogeneity, yet treatment often relies on peripheral blood eosinophil counts. Direct assessment of airway eosinophilia—using bronchoalveolar lavage (BAL) and bronchial mucosal biopsy—may better identify patients at risk of exacerbations.


Methods
We prospectively recruited 25 patients with post-bronchodilator airflow obstruction, defined as FEV1/FVC < 0.70. All underwent a comprehensive clinical assessment, laboratory analysis, induced sputum collection, BAL, and bronchial mucosal biopsy. Eosinophil counts were quantified in peripheral blood, sputum, BAL fluid, and bronchial mucosa, and correlated with clinical parameters, pulmonary function, and exacerbation history.


Results
Eosinophilia was detected in BAL fluid in 28% of patients and in bronchial mucosa in 20%. In contrast, peripheral blood eosinophilia was present in 48%, whereas sputum eosinophilia was uncommon at 4%. Patients with BAL eosinophilia exhibited significantly elevated bronchial mucosal eosinophil counts. Importantly, bronchial mucosal eosinophilia correlated with a higher rate of acute exacerbations during the previous year and more pronounced radiographic hyperinflation. No significant differences were observed in GOLD classification or spirometric values between groups.


Conclusion
Bronchial mucosal eosinophilia in the bronchial wall, rather than eosinophil counts in peripheral blood or sputum, was associated with exacerbation frequency in COPD. These results suggest that assessing eosinophilic inflammation at the mucosal level is associated with exacerbation risk and that compartment-specific inflammatory phenotyping in COPD management warrants further investigation.