Research of Endobronchial Optical Coherence Tomography in Pre-stage of Chronic Obstructive Pulmonary Disease

Control group

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

Pre-stage of Chronic Obstructive Pulmonary Disease (Pre-COPD)

Patients exhibit early pulmonary abnormalities, such as, CT scans show the presence of emphysema, bullae, and air trapping; pulmonary function manifested as preserved ratio impaired spirometry (PRISm). PRISm was defined as a normal ratio \[the forced expiratory volume in one second (FEV1) / forced vital capacity (FVC) ≥ 0.7\] after inhalation of a bronchodilator, but impaired ventilatory function \[percentage of forced expiratory volume in the first second to the expected value (FEV1%) and/or percentage of FVC to the expected value (FVC%) \< 80%\], with concurrent structural changes in the lungs (such as emphysema) and/or physiological abnormalities (such as hyperinflation, decreased diffusion capacity, rapid decline in FEV1 )

Chronic Obstructive Pulmonary Disease (COPD)

COPD was diagnosed based on GOLD guideline \[1\]; 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