Positive effects of oxygenation on simulated post-transplantation lung edema and pulmonal arterial resistance

Objective: Ischemia-reperfusion injury still causes severe problems after lung transplantation. It is supposed that systemic oxygen supply to the transplanted lungs could improve transplantation outcome. By using an ex vivo model of isolated perfused and ventilated rabbit lungs we investigated the influence of systemic oxygenation on pulmonary function during simulated transplantation.

Methods: The heart-lung blocks of 12 New Zealand White rabbits (2.22±0.4kg) were excised and transferred to a 37°C water-heated artificial thorax chamber. Negative pleural pressure ventilation was initiated and perfusion with recirculating, albumin-containing Tyrode-Solution was slowly increased to a constant end flow of 100ml/min. The lungs were arranged in a stable perfusion and ventilation mode for 30min. Afterwards lungs underwent a flush-perfusion with Perfadex^® Solution, followed by an ischemic storage for 4h on ice, thereafter ventilation and reperfusion for 2h were continued to simulate a transplantation situation (oxygenated group, pulmonary artery pO₂=120mmHg). In another series the perfusate inflow was additionally gassed with nitrogen (connecting a fiber oxygenator) to simulate deoxygenation (deoxygenated group, pulmonary artery pO₂=50mmHg). Hemodynamic and ventilatory parameters (pulmonary artery pressure (PAP), pulmonary compliance, pulmonary resistance, lung weight) were continuously detected.

Results: After 2h reperfusion time in the oxygenated group we found a significant lower PAP and lung weight compared to the deoxygenated group (p<0.05). PAP and lung weight steadily increased after reestablishment of lung perfusion (PAP: initial 8.78±0.89 cmH₂O, 30min reperfusion 7.2±1.48 cmH₂O, 2h reperfusion 11.5±1.06 cmH₂O; lung weight: initial 22.1±1.32g, 30min reperfusion 26.1±1.87g, 2h reperfusion 35.4±4.23g). This development was significantly influenced by the intravascular pO₂ (PAP: initial 9.65±0.43 cmH₂O, 30min reperfusion 7.92±0.52 cmH₂O, 2h reperfusion 8.02±0.63 cmH₂O; lung weight: initial 17.9±1.54g, 30min reperfusion 19.0±1.68g, 2h reperfusion 21.5±2.29g, p<0.05).

Conclusions: Oxygenation of the lung perfusate during simulated transplantation attenuates post transplant edema formation and decreases pulmonal arterial hypertension. Transfering this to the surgical situation, revascularisation of bronchial arteries after lung transplantation might initiate positive effects in the early phase after lung transplantation.