Importance of left atrial pressure during ex vivo lung perfusion

Ex vivo lung perfusion (EVLP) allows for the evaluation and treatment of donor lungs before transplant. Different EVLP strategies have been described using either an open left atrium (LA) (pressure of 0 mm Hg) or closed LA (pressure of 5 mm Hg). We hypothesized that maintaining a physiologic positive LA pressure during EVLP is protective to the lung.

Pig lungs were flushed with Perfadex, retrieved and stored at 4°C for 4 hours [short cold ischemic time (CIT), n = 10] or 18 hours (prolonged CIT, n = 8). Subsequently, lungs underwent normothermic EVLP for 12 hours using either an open or closed LA technique. A linear mixed effect model was used to compare functional parameters between the 2 groups.

After short CIT, 12-hour EVLP could not be completed in 4 of 5 open atrium cases due to significant pulmonary edema. Lung injury was evident in this group after 7 hours of EVLP, demonstrating an increase in pulmonary vascular resistance (p < 0.001) and peak inspiratory pressure (p = 0.001), and a decrease in lung compliance (p < 0.001) and perfusate oxygenation (p = 0.04). In contrast, in the closed atrium group, all lungs completed 12 hours of EVLP with stable functional parameters. At the end of the experiment, the wet/dry ratio (p = 0.015) and lung edema score (p = 0.02) were significantly worse in the open LA group compared with the closed LA EVLP group. Similar findings were observed in the prolonged CIT group.

The use of a closed atrial technique to create a controlled positive LA during EVLP leads to significantly less edema and superior lung physiology.