1. Department of Cardiothoracic Surgery, Division of Cardiovascular and Pulmonary Diseases, Oslo University Hospital, Rikshospitalet, Norway;
2. Faculty of Medicine, University of Oslo, Norway;
3. Department of Respiratory Medicine, Division of Cardiovascular and Pulmonary Diseases, Oslo University Hospital, Rikshospitalet, Norway;
4. Oslo Centre for Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, Norway