Open-lung ventilation versus no ventilation during cardiopulmonary bypass in an innovative animal model of heart transplantation.

Open-lung ventilation during cardiopulmonary bypass (CPB) in patients undergoing heart transplantation (HTx) is a potential strategy to mitigate postoperative acute respiratory distress syndrome (ARDS). We utilized an ovine HTx model to investigate whether open-lung ventilation during CPB reduces postoperative lung damage and complications. Eighteen sheep from an ovine HTx model were included, with ventilatory interventions randomly assigned during CPB: the OPENVENT group received low tidal volume (V _T ) of 3 mL/kg and positive end-expiratory pressure (PEEP) of 8 cm H ₂ 0, while no ventilation was provided in the NOVENT group as per standard of care. The recipient sheep were monitored for 6 h post-surgery. The primary outcome was histological lung damage, scored at the end of the study. Secondary outcomes included pulmonary shunt, driving pressure, hemodynamics and inflammatory lung infiltration. All animals completed the study. The OPENVENT group showed significantly lower histological lung damage versus the NOVENT group (0.22 vs 0.27, p = 0.042) and lower pulmonary shunt (19.2 vs 32.1%, p = 0.001). In addition, the OPENVENT group exhibited a reduced driving pressure (9.6 cm H ₂ O vs. 12.8 cm H ₂ O, p = 0.039), lower neutrophil (5.25% vs 7.97%, p ≤ 0.001) and macrophage infiltrations (11.1% vs 19.6%, p < 0.001). No significant differences were observed in hemodynamic parameters. In an ovine model of HTx, open-lung ventilation during CPB significantly reduced lung histological injury and inflammatory infiltration. This highlights the value of an open-lung approach during CPB and emphasizes the need for further clinical evidence to decrease risks of lung injury in HTx patients.
Competing Interests: Declarations. Ethics approval and consent to participate: The project was approved by Queensland University of Technology (QUT) Animal Ethics Committee (Approval #16-1109). Ratified by the University of Queensland AEC (QUT/393/17/QUT), experiments were performed in accordance with the National Health and Medical Research Council (NHMRC) Australian Code of Practice for the Care and Use of Animals for Scientific Purposes (8th Edition 2013), the Animal Care and Protection Act 2001 (QLD) and complied with the ARRIVE Guidelines. Consent for publication: Not applicable. Competing interests: Professor John Fraser is the CEO of the Quantum Medical Innovation Fund and De Motu Cordis Pty Limited. He is also the co-founder of BiVACOR™ Pty Ltd. In addition, Prof. Fraser and his research group collaborate with Australian Red Cross Lifeblood, Fisher and Paykel healthcare, Mallinckrodt Pharmaceuticals and CSL. Professor Fraser receives reimbursement for travel costs when presenting research created collaboration with Fisher and Paykel Healthcare. Professor David McGiffin provides consultancy services to Abbott. This has no direct impact on the contents of the manuscript. The other authors do not have any conflict of interest.
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