412 Quantitative air trapping analysis in lung transplant recipients

Objectives/Goals: Bronchiolitis obliterans syndrome (BOS), a form of chronic lung allograft dysfunction (CLAD) that primarily affects the small airways, is often diagnosed too late using standard pulmonary function tests. This project aims to evaluate whether quantitative air trapping analysis can serve as an early diagnostic tool for BOS. Methods/Study Population: We performed a retrospective analysis of 134 computed tomography scans with inspiratory and expiratory protocols from 73 lung transplant recipients (48 male, 25 female). Quantitative air trapping analysis was performed by VIDA Diagnostics using a supervised machine learning technique called disease probability measure (DPM). Results/Anticipated Results: We found that lung transplant recipients exhibit significantly more air trapping compared to healthy controls and other small airway diseases, such as long COVID and cystic fibrosis. Notably, lung transplant recipients showed increased air trapping in the upper lobes. However, when separating participants into CLAD and non-CLAD groups, those meeting criteria for CLAD had significantly more air trapping in the left lower lobe. Additionally, only 2 out of 16 participants meeting CLAD criteria had less than 20% air trapping in their lungs, suggesting early involvement of the small airways. Discussion/Significance of Impact: Quantitative air trapping analysis seems to be an important diagnostic modality in the early detection of lung transplant-related small airway disease. Prospective longitudinal studies are needed to evaluate the spatial pathophysiology in these patients and to determine whether early air trapping can predict the development of CLAD.