Flow Controlled Ventilation during EVLP Improves Oxygenation and Preserves Alveolar Recruitment

Abstract

Ex vivo lung perfusion (EVLP) is considered a useful platform to evaluate, preserve and recondition grafts prior to lung transplantation (LTx). Reducing physical stress due to standard volume-controlled ventilation (VCV), might further prolong EVLP in time and reduce ventilator induced lung injury (VILI). An innovative approach might be the use of flow-controlled ventilation (FCV), a ventilation mode which controls inspiratory and expiratory flow. These properties can reduce atelectrauma and volutrauma related to standard VCV. This is the first study to evaluate the use of FCV during EVLP in a porince model. Porcine lungs were mounted on EVLP after 2 hours of warm ischemia and divided into 2 groups (n=7/group). EVLP was maintained for 6 hours and physiological parameters were continuously recorded. In the first group, lungs on EVLP were ventilated standardly (VCV, 7 ml/kg). In the second group, lungs were ventilated using FCV (7ml/kg). After EVLP, W/D ratios were taken of the right lung and the left lung was frozen while inflated in liquid nitrogen vapors and CT scanned. Results are demonstrated in figure 1. Pulmonary vascular resistance (PVR) was comparable between VCV and FCV (p=0.52). FCV significantly increased oxygenation (P/F ratios) (p=0.01), and better maintained dynamic compliance (p=0.03). There was no difference in W/D ratios between the groups (p=0.16). CT density measurements were decreased by FCV (p=0.05). FCV is feasible to ventilate pulmonary grafts during EVLP and improves oxygenation. The lower decline in compliance and lower CT density measurements in FCV might indicate a better preservation of alveolar recruitment since extravascular water content (W/D ratio) was similar between both groups. In conclusion, FCV ventilation might reduce injury related to standard volume-controlled ventilation. Using FCV mode during EVLP might stabilize and prolong EVLP time in the future and open the perspective to further actively recondition grafts.