Feasibility and accuracy of direCt Lung Ultrasound Evaluation (CLUE) technique to monitor extravascular lung water in porcine lungs

Objectives: Extravascular lung water (EVLW) precedes deterioration of pulmonary function. Current tools to assess EVLW in a setting of donor lung procurement and ex vivo lung perfusion (EVLP) are either subjective or not feasible. Therefore, a direCt Lung Ultrasound Evaluation (CLUE) has been introduced. This study reassesses the feasibility and accuracy of CLUE by measuring its' correlation with lung weight, wet-to-dry ratio (W/D ratio), dynamic compliance, and pulmonary vascular resistance (PVR) in a porcine model.

Methods: CLUE images, lung weight, dynamic compliance and PVR were recorded and lung samples for W/D ratio were taken before and after EVLP. CLUE score was calculated based on B-lines on images taken at each point of the lung using an established equation.

Results: Eighteen porcine lungs were included. Total median of CLUE score, lung weight, W/D ratio and PVR increased significantly, while median of dynamic compliance decreased significantly after EVLP. Total median CLUE score increased significantly in all four surfaces after EVLP with equally high CLUE scores in posterior and diaphragm lines. CLUE score demonstrated a significant strong positive correlation with lung weight (r = 0.825) and W/D ratio (r = 0.837), while CLUE's correlation with dynamic compliance and PVR was significantly moderate to strong (r= - 0.669, r = 0.695, respectively).

Conclusions: CLUE technique is feasible to assess EVLW in donor lungs after procurement and during EVLP. CLUE score correlated significantly with lung weight, W/D ratio, dynamic compliance and PVR. Transplant suitability of a donor lung may not solely depend on CLUE evaluation.