In situ expansion capacity evaluation of terminal alveoli in chronic obstructive pulmonary disease using an ultrathin optical coherence tomography catheter

Morphological structural changes in the peripheral alveoli serve as critical indicators for the early pathological features of chronic obstructive pulmonary disease (COPD). Endoscopic optical coherence tomography (OCT) has emerged as a valuable diagnostic tool for COPD, enabling the assessment of airway mucosa, smooth muscle thickness, lumen diameter, lumen area, and airway wall area. However, conventional transbronchial OCT imaging catheters are limited in size, restricting their access to terminal bronchioles and thereby impeding the morphological and structural analysis of peripheral alveoli. In this study, we present a bronchial ultrathin OCT (Bronchial-uOCT) imaging catheter with an outer diameter of 380 µm, an axial resolution of 8.4 µm, and a lateral resolution of 9.3 µm. Using New Zealand rabbit COPD models, we achieved real-time in situ 3D volumetric imaging of terminal alveoli. Statistical analysis revealed a difference of 5 times in the alveolar area between normal and COPD pathological groups (P = 0.00018). Quantitative analysis of expansion compliance revealed significant differences in the growth rate and trend of the alveolar area between the normal group and the COPD pathology group. Furthermore, the opening direction of the curve obtained through power law fitting may help diagnose COPD. These findings highlight bronchial-uOCT as a clinically significant approach capable of in situ visualization of alveolar structures in the terminal bronchioles, offering a promising approach for the early diagnosis and assessment of COPD.