1. Department of Occupational Medicine; University Medical Center Freiburg; Freiburg; Germany
2. Department of Anaesthesia and Critical Care Medicine; Ortenau Clinical Center; Offenburg; Germany
3. Department of Congenital Heart Disease; University Heart Center Freiburg; Freiburg; Germany
4. Department of Anaesthesia and Critical Care Medicine; University Medical Center Freiburg; Freiburg; Germany