1 Department of Anaesthesiology and Critical Care, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany. Johannes.kalbhenn@uniklinik-freiburg.de.
2 Department of Anaesthesiology and Critical Care, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.