DireCt Lung Ultrasound Evaluation (CLUE): A novel technique for monitoring extravascular lung water in donor lungs

Background: Extravascular lung water (EVLW) could change in donor lungs in a time-dependent fashion during procurement or ex-vivo lung perfusion (EVLP) and may vary across different zones. Current techniques for EVLW assessment are either subjective, general estimation, or not feasible in the clinical setting. An accurate and non-invasive diagnostic tool for EVLW would be desirable for donor lung assessment and management. Therefore, we studied the feasibility and accuracy of direCt Lung Ultrasound Evaluation (CLUE) technique.

Methods: Eleven lungs were utilized for the human model and 6 lungs for the porcine model. Lungs underwent EVLP for 2 hours. In CLUE, ultrasound images were taken directly from the lungs. A scoring system was created for each point based on the percentage of B-lines. Images were graded according to the degree of edema. An equation was used to calculate total lung and lobe scores based on number of images of each grade.

Results: CLUE point score correlated with wet/dry ratio in human and porcine models (n = 99, r = 0.863, p < 0.001; and n = 31, r = 0.916, p < 0.001, respectively). CLUE total lung score correlated with lung weight (n = 19, r = 0.812, p < 0.001; and n = 12, r = 0.895, p < 0.001, respectively). CLUE lobe score correlated negatively with partial pressure of oxygen/fraction of inspired oxygen ratio in the human model (n = 20, r = -0.775, p < 0.001).

Conclusions: EVLW monitoring in donor lungs with CLUE after procurement is feasible and CLUE scores were found to be significantly correlated with lung weight, wet/dry, and PaO₂/FIO₂ ratio.