1 Centre for Patient Centered Heart and Lung Research, Department of Cardiothoracic Surgery, Oslo University Hospital, Kirkeveien 166, 0450 Oslo, Norway.
2 Department of Health Sciences in Gjøvik, Norwegian University of Science and Technology, 2802 Gjøvik, Norway.
3 Department of Nursing and Health Promotion, Faculty of Health Sciences, Oslo Metropolitan University, St. Olavs Plass, Oslo, Norway.