1. Department of Respiratory Diseases and Allergy, Aarhus University Hospital, Aarhus, Denmark
2. Research Unit of Internal Medicine, Oulu University Hospital and University of Oulu, Oulu, Finland
3. Department of Respiratory Medicine, Vejle Hospital, Vejle, Denmark
4. Department of Research and Development, Physio R&D ApS, Frederiksberg, Denmark
5. Department of Communication Studies, University Carlos III of Madrid, Madrid, Spain
6. Health Research Institute, University of Almeria, Almeria, Spain