Ultra-protective ventilation combined with V-V ECMO has a preferable therapeutic effect on Acute Respiratory Distress Syndrome: An experimental study in aged Beagle dogs

Background: To assess the optimal mechanical ventilation strategies during venovenous extracorporeal membrane oxygenation (V-V ECMO) in aged dogs with severe respiratory distress syndrome. Methods: Beagle dogs aged 10-12 years old were randomized assigned(n = 6 per group) to control or three different ventilation strategy groups: conventional ventilation strategy (CV) group, protective ventilation strategy (PV) group and ultra-protective ventilation strategy (UPV) group. ARDS model was established and V-V ECMO was used in all the dogs of CV, PV and UPV groups. Gas exchange data including blood partial pressure of oxygen (PaO 2 ), partial pressure of carbon dioxide (PaCO 2 ) and ventilator-induced lung injury(VILI) data including airway plateau pressure (Pplat), extravascular lung water index (EVLWI) and lung compliance were continuously monitored. After continuous treatment for 24 hours, lung tissue were collected to assess the histological examination and the inflammatory factors expression. Results: For VILI data, the 24-hour lung compliance of UPV group was significantly higher than CV and PV groups. Pplat and EVLWI were significantly lower in UPV group than those in the other two ventilation strategy groups. And the pathology study demonstrated that lower lung injury scores of the UPV group than the CV or the PV group. Results of immunohistochemistry showed that the expression of IL-6, IL-10, and TNF-α were significantly lower in UPV group than PV and CV groups, which further confirmed the effectiveness of UPV strategy. Conclusions: UPV strategy showed significant advantage on decreasing lung injury and the inflammatory responses in the aged dog of severe ARDS model supported with V-V ECMO.