• Johannes Schmidt, Christin Wenzel, Marlene Mahn, Sashko Spassov, Heidi Cristina Schmitz, Silke Borgmann, Ziwei Lin, Jörg Haberstroh, Stephan Meckel, Sebastian Eiden, Steffen Wirth, Hartmut Buerkle, and Stefan Schumann.
• From the Department of Anesthesiology and Critical Care (JS, CW, MM, SS, HCS, SB, ZL, SW, HB, SS), Experimental Surgery, Centre for Experimental Models and Transgenic Service (JH) and Department of Neuroradiology (SM, SE), Medical Centre - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
• Eur J Anaesthesiol. 2018 Oct 1; 35 (10): 736744736-744.

BackgroundIn contrast to conventional mandatory ventilation, a new ventilation mode, expiratory ventilation assistance (EVA), linearises the expiratory tracheal pressure decline.ObjectiveWe hypothesised that due to a recruiting effect, linearised expiration oxygenates better than volume controlled ventilation (VCV). We compared the EVA with VCV mode with regard to gas exchange, ventilation volumes and pressures and lung aeration in a model of peri-operative mandatory ventilation in healthy pigs.DesignControlled interventional trial.SettingAnimal operating facility at a university medical centre.AnimalsA total of 16 German Landrace hybrid pigs.InterventionThe lungs of anaesthetised pigs were ventilated with the EVA mode (n=9) or VCV (control, n=7) for 5 h with positive end-expiratory pressure of 5 cmH2O and tidal volume of 8 ml kg. The respiratory rate was adjusted for a target end-tidal CO2 of 4.7 to 6 kPa.Main Outcome MeasuresTracheal pressure, minute volume and arterial blood gases were recorded repeatedly. Computed thoracic tomography was performed to quantify the percentages of normally and poorly aerated lung tissue.ResultsTwo animals in the EVA group were excluded due to unstable ventilation (n=1) or unstable FiO2 delivery (n=1). Mean tracheal pressure and PaO2 were higher in the EVA group compared with control (mean tracheal pressure: 11.6 ± 0.4 versus 9.0 ± 0.3 cmH2O, P < 0.001 and PaO2: 19.2 ± 0.7 versus 17.5 ± 0.4 kPa, P = 0.002) with comparable peak inspiratory tracheal pressure (18.3 ± 0.9 versus 18.0 ± 1.2 cmH2O, P > 0.99). Minute volume was lower in the EVA group compared with control (5.5 ± 0.2 versus 7.0 ± 1.0 l min, P = 0.02) with normoventilation in both groups (PaCO2 5.4 ± 0.3 versus 5.5 ± 0.3 kPa, P > 0.99). In the EVA group, the percentage of normally aerated lung tissue was higher (81.0 ± 3.6 versus 75.8 ± 3.0%, P = 0.017) and of poorly aerated lung tissue lower (9.5 ± 3.3 versus 15.7 ± 3.5%, P = 0.002) compared with control.ConclusionEVA ventilation improves lung aeration via elevated mean tracheal pressure and consequently improves arterial oxygenation at unaltered positive end-expiratory pressure (PEEP) and peak inspiratory pressure (PIP). These findings suggest the EVA mode is a new approach for protective lung ventilation.

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