1. Department of Physics, University of Helsinki, Helsinki, Finland
2. Medical Imaging Center, Helsinki University Hospital, Helsinki, Finland
3. Hedenstierna Laboratory, Department of Surgical Sciences, Uppsala University, Sweden
4. Department of Pediatric Intensive Care, Amiens University Hospital, Amiens, France
5. Anesthesiological Investigations Unit, University Hospitals of Geneva, Geneva, Switzerland
6. Maquet Critical Care, Solna, Sweden; and
7. University of Grenoble EA-7442 and Department of Clinical Physiology, Sleep and Exercise, Grenoble University Hospital, Grenoble, France