A CLUE for Better Assessment of Donor Lungs: Novel Technique in Clinical Ex-Vivo Lung Perfusion

Abstract

Direct lung ultrasound evaluation (CLUE) technique was proven to be an accurate method for monitoring extravascular lung water in donor lungs during ex-vivo lung perfusion (EVLP) in porcine and human lung models. The aim of this study was to examine the application of CLUE in the clinical setting. Lungs were evaluated in acellular EVLP with standard protocol. Ultrasound images were obtained at each point of 4 lines passing through the anterior, lateral, posterior, and diaphragmatic surfaces of each lung. Images were graded according to the percentage of B-lines and presence of consolidation. CLUE scores were calculated at the beginning (initial) and the end (final) of EVLP for the whole lung, each side and lobe using this equation: CLUE Score = (No. of Grade 1 images x 1 + No. of Grade 2 images x 2 + No. of Grade 3 images x 3 + No. of Grade 4 images x 4 + No. of Consolidation images x 5) / Total No. of images taken. In our clinical EVLP program, 36 lungs from 18 donors were evaluated by CLUE. Eighteen lungs were deemed suitable and were transplanted (8 double & 2 single) with no hospital mortality. There were no cases of primary graft dysfunction (PGD) grade 2 observed and one recipient had PGD 3 at 72 hours. Final CLUE score was significantly lower in suitable lungs compared to non-suitable (0.86 ± 0.4 vs 1.80 ± 0.3, p < 0.001). CLUE score had the highest area under the receiver-operating characteristic curve (0.98, with threshold of 1.4, specificity 94% & sensitivity 92%) when compared to other evaluation parameters like Δ PO2 (0.68) and dynamic compliance (0.89). Initial CLUE score of standard donor lungs which were perfused for logistic reasons was significantly lower than marginal lungs (0.58 ± 0.3 vs 1.38 ± 0.4, p = 0.001) with threshold of 0.93. Initial CLUE score was significantly higher in lungs put in prone position compared to the supine group (1.56 ± 0.5 vs 1.12 ± 0.5, p = 0.004). The change in initial to final CLUE score in prone group showed significant improvement (1.00 ± 0.4 vs 1.69 ± 0.4, p = 0.004) especially in the upper lobes (1.34 ± 0.8 vs 2.67 ± 0.7, p = 0.009). CLUE technique shows the highest accuracy in evaluating donor lungs for transplant compared to other parameters used in EVLP. CLUE can help in improving the outcomes of lung transplant by guiding decision making through the whole process of EVLP and providing a comprehensive precise assessment of individual lungs and lobes.