1. Faculty of Health, Welfare and Organization, Ostfold University College, Postal Box Code 700, 1757 Halden, Norway
2. Department of Anesthesia, Ostfold Hospital Trust, Postal Box Code 300, 1714 Grålum, Norway
3. Department of Health Sciences, Faculty of Health, Science, and Technology, Karlstad University, SE-651 88 Karlstad, Sweden