1. Department of Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
2. Department of Anesthesiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
3. Department of Biomedical Signals and Systems, University of Twente, Enschede, The Netherlands
4. eHealth Group, Roessingh Research and Development, Enschede, The Netherlands