Although forced expiratory volume in one second (FEV1) remains the gold standard for staging COPD, the association between airway remodeling and airflow limitation remains unclear.
Endobronchial optical coherence tomography (EB-OCT) was performed to assess the association between disorders of large- and medium-to-small-sized airways and COPD staging. We also evaluated small-airway architecture in heavy-smokers with normal FEV1 (SNL) and healthy never-smokers.
We recruited 48 COPD patients (stage Ⅰ, n=14; stage Ⅱ, n=15; stage Ⅲ-Ⅳ, n=19), 21 SNL, and 17 healthy never-smokers. Smoking history inquiry, spirometry, chest computed tomography, bronchoscopy and EB-OCT were performed. Mean luminal diameter (Dmean), inner luminal area (Ai), and airway wall area (Aw) of generation 3∼9 bronchi were measured using EB-OCT.
Patients with more advanced COPD demonstrated greater abnormality of airway architecture in both large- and medium-to-small-sized airways, followed by SNL and never-smokers. Abnormality of airway architecture and EB-OCT parameters in SNL were comparable to those with stage I COPD. FEV1% predicted correlated with D and Ai of generation 7∼9 in COPD; however, neither D nor Ai of generation 3∼6 correlated with FEV1% in stage Ⅰ and Ⅱ COPD and SNL.
FEV1-based COPD staging partially correlates with small-airway disorders in stage Ⅱ-Ⅳ COPD. EB-OCT-detected small airway abnormalities correlate with FEV1-based staging in COPD and identify early pathology in healthy heavy-smokers.