The pre-stage of Chronic Obstructive Pulmonary Disease (Pre-COPD) is challenging to diagnose. However, identifying Pre-COPD is a crucial step in the prevention and management of COPD. Endobronchial optical coherence tomography showed the value of diagnosis in Pre-COPD and COPD in previous researchs.

We recruited COPD patients (stage I-II, n=15; stage III-IV, n= 15), Pre-COPD (n= 20) and healthy never-smokers (healthy human, n=21). Age,gender,BMI, smoking history, spirometry, chest computed tomography (CT), bronchoscopy and EB-OCT were performed. Inner luminal area (Ai) and airway wall area (Aw) of bronchi which inner perimeter was 10mm, 20mm and 30mm were measured using EB-OCT respectively. By analyzing and studying the above situation, we aim to discover the application value of OCT in Pre-COPD

Inclusion Criteria:

• non-smoking with normal lung function, no other pulmonary diseases besides pulmonary nodule as indicated by chest computed tomography (CT).

Exclusion Criteria:

• (1) patients with contraindication of bronchoscopy, (2) patients who are participating in other clinical studies, (3) patients with poor compliance who are believed by the researchers to be unable to cooperate for the completion of the examination and follow-up, and (4) women who were pregnant.

Pre-COPD: Pre-COPD was diagnosed based on GOLD 2022; Patients exhibit early pulmonary abnormalities, such as, CT scans show the presence of emphysema, bullae, and air trapping; COPD: COPD was diagnosed based on GOLD guideline; No acute exacerbations within 4 weeks; CT scans show no other pulmonary diseases besides COPD; pulmonary function test results were available from within the last 3 days. All COPD patients were treatment-naive except for those with at stage III-IV who received maintenance therapy.