Is it possible to further improve the function of pulmonary grafts by extending the duration of lung reconditioning using ex vivo lung perfusion?

Background: The method of ex vivo lung perfusion (EVLP) has been suggested as a reliable means of differentiating between "good" and "poor" pulmonary grafts in marginal donors as, when grafts identified as good by this method are transplanted, the results do not differ from those using lungs fulfilling standard criteria. The EVLP method is also thought to improve pulmonary grafts by reducing lung edema and eliminating lung atelectasis. In the present study, we investigated whether the pulmonary graft could be further improved by extending the duration of EVLP. Methods and Materials: Six Landrace pigs were used. The lungs were reconditioned and evaluated, using the EVLP method, as double lungs. After the initial evaluation, EVLP was continued for a further 90 minutes. Results: The arterial oxygen level (pO(2)) was 60.8 +/- 4.8 kPa after the standard 60 minutes of EVLP and 67.1 +/- 2.2 kPa after 150 minutes (p = 0.48). The pulmonary vascular resistance was 453 +/- 78 dyne*s/cm(5) after 60, 90, 120 and 150 minutes of EVLP (p = 1.0). The pulmonary artery pressure was 17.8 +/- 1.0 mmHg after 60, 90, 120, and 150 minutes of EVLP (p = 1.0) and the pulmonary artery flow was 3.5 +/- 0.4 l/min after 60, 90, 120, and 150 minutes of EVLP (p = 1.0). The mean weight of the pulmonary grafts after harvesting was 574 +/- 20 g at the beginning of EVLP 541 +/- 24 g and, after 150 min of EVLP, 668 +/- 33 (p = 0.011). Conclusions: The blood gases and hemodynamic parameters in the pulmonary grafts did not improve as a result of the extra 90 minutes of EVLP. However, the weight of the pulmonary graft increased significantly with increasing duration of EVLP, indicating lung perfusion injury.