Regional gas exchange evaluation during ex vivo lung perfusion in a swine model of localized lung dysfunction

Background: Ex vivo lung perfusion (EVLP) allows the evaluation of lungs that do not meet standard transplantation criteria. Current procedures do not permit the identification of regional functional deficits. We investigated the feasibility of assessing lobar gas exchange during EVLP in a swine model. Methods: In five healthy swine, lungs were procured with beating heart and connected to an open-atrium EVLP circuit. Each pulmonary vein was cannulated for lobar perfusate sampling. After baseline assessment, the left inferior bronchus (LIB) and then the left superior bronchus (LSB) were temporarily clamped to simulate localized injury. At each step, perfusate gas analyses from each vein and the left atrium (LA), lung mechanics, pulmonary hemodynamics, and computed tomography (CT) were obtained. Results: At baseline, no differences were observed between LA and lobar samples. Occlusion of LIB and LSB produced up to 95% non- or poorly aerated tissue in the affected lobe, with lobar shunt increasing to 97% [88%-103%] (LIB) and 97% [78%-106%] (LSB). Corresponding lobar PaO2/FiO2 fell to 47 [46-54] and 45 [43-67] mmHg, whereas LA-mixed venous blood maintained higher values (299 [188-373] and 349 [347-377] mmHg, respectively). Bronchial occlusions caused overall significant worsening of lung function, including increased pulmonary vascular resistance, and reduction in total air lung volume and normally aerated tissue on CT scan analysis. In Left Inferior Lobe (LIL), histological samples showed significant interstitial congestion and alveolar hemorrhage. Conclusions: Lobar-specific perfusate gas analysis during EVLP provides accurate functional assessment and enables the localization of lung injury, potentially improving graft evaluation before transplantation.