The Assessment of Lobe Oxygenation by Differential Blood Gas Analysis on Ex-Vivo Lung Perfusion May Predict Postoperative Outcomes

Abstract

Lung assessment of marginal donor lungs on ex vivo lung perfusion (EVLP) can be challenging due to limited objective parameters. Currently, the significance of isolated differential analysis of blood gas (ABG) from each lobar pulmonary vein is not clear. The aim of this study is to identify the impact of differential ABG (D-ABG) on EVLP evaluation, and compare the D-ABG with the post-transplant outcomes. From Feb 2016 to August 2019, 110 EVLP lungs from 57 donors were analyzed for this study. Donor lungs were perfused with an acellular EVLP protocol, and transplant suitability of lungs was evaluated based on standard EVLP parameters. D-ABGs were taken from each pulmonary vein at the same time of standard evaluation. In transplanted EVLP lungs, primary graft dysfunction (PGD) was assessed at 72 hours. In the favorable group (defined as PGD grade 0-1), both PaO2/FiO2 (P/F) ratio at left atrium (P/F LA) and P/F ratio at lower lobe pulmonary vein (P/F LPV) were significantly higher than that of the unfavorable group (non-suitable or PGD grade 2-3) [LA, 526 (466-574) vs. 437 (386-499) mmHg, P < 0.001; LPV, 409 (349-452) vs. 332 (250-364) mmHg, p <0.001]. In receiver operating characteristic curve analysis for unfavorable, P/F ratio LPV showed the highest AUC with threshold of 384, sensitivity 0.88 and specificity 0.63 than that of other standard parameters (Table 1). Regarding PGD at 72 hours in transplanted lungs, P/F LA on EVLP assessment was not different between PGD≥2 and PGD≤1 groups [526 (466-574) vs. 510 (433-513) mmHg, p = 0.307, Figure], while P/F LPV in PGD≥2 was significantly lower than that in PGD≤1 [352 (334-398) vs. 409 (349-452) mmHg, p = 0.046]. These results suggest that D-ABG on EVLP could provide additional, valuable information for evaluation. The deterioration of lobe oxygenation might be masked throughout whole lung ABG; however, low D-ABG of the lower lobe may predict a greater incidence of high-grade PGD after lung transplantation.