Ventilation Protocol in a New Experimental Ex Vivo Single-Lung Perfusion Model for Transplantation

Silvia Ramos Cerro1, Ignacio Garutti Martínez1, Alberto Fernández Peña1, Ángela Puig Ramos1, Carlos Simón Adiego2, Elena Vara Ameigeiras3
1 Department of Anesthesiology and Intensive Care and 2 Department of Thoracic Surgery, Gregorio Marañon University General Hospital, Madrid, Spain; and 3 Department of Biochemistry and Molecular Biology III, Complutense University of Madrid, Madrid, Spain.

BACKGROUND AND GOAL OF STUDY: Nowadays, only about 15% of donated 
lungs are used for transplantation while up to 20% of patients die while waiting for a lung transplant. Ex vivo lung perfusion (EVLP) has been shown to be a useful technique for preservation, assessment and reconditioning of donor lungs. Clinical and experimental research is needed to address many unanswered questions about EVLP.
To assess the viability of a new porcine single lung EVLP model for assessment/reconditioning of non heart-beating donor lungs. The detailed technique for ex vivo lung ventilation is described. 

MATERIAL AND METHODS: Fifteen pigs were submitted to a left lung transplant. Donor lungs were harvested after electrical cardiac arrest and a 30-minute period of warm ischemia.  The left lung was then submitted to a three-hour period of cold preservation. In SHAM group (n=5), left lung was then implanted and reperfusion was maintained for two hours. In EVLP group (n=10) donor lungs were assessed/reconditioned for 60 minutes in a normothermic EVLP circuit using an acellular perfusate and leaving the left atrium open. Perfusate flow and temperature were gradually increased to 16% of the calculated cardiac output and 370C respectively. Ventilation was started after 20-25 minutes, when temperature of perfusate reached 320C. Ventilatory parameters: rate up to 14/min; tidal volume up to 4 mL/kg (donor body weight); PEEP= 5 cm H2O; FiO2=40%; I:E ratio=1:2; maximum airway pressure=20 cm H2O. Airway resistance and pressure, lung compliance and perfusate gases were measured 30 and 60 minutes after the beginning of perfusion. Lung was then recooled, implanted and reperfused for two hours. In both groups, left pulmonary venous gases were measured 60 and 120 minutes after the beginning of reperfusion. 

RESULTS AND DISCUSSION: Lung airway resistance decreased significantly during EVLP (P<0.05) while lung compliance increased (P<0.05). The oxygenation capacity of the lung improved during EVLP (PaFiO2 75±37 vs 335±89) at 30min and 60min respectively (p<0.01). The oxygenation capacity of the implanted lungs after two hours of reperfusion was significantly better in the EVLP group than in the SHAM group (P<0.05). In EVLP group, pulmonary vein gases of transplanted lungs after reperfusion did not significantly differ from arterial gases from donor pigs.

CONCLUSION: The present experimental model has proven to be feasible and suitable to investigate reconditioning strategies for damaged donor lungs.

Ventilation protocol in a new experimental ex vivo single-lung perfusion model for transplantation