1. Institute of Nursing Science, University of Basel, Bernoullistraß 28, 4056 Basel, Switzerland
2. Department of Cardiovascular Surgery, University Hospital of Bern, Freiburgstraß 1, 3000 Bern, Switzerland
3. Department of Health Promotion and Development, School of Nursing, University of Pittsburgh, 350 Victoria Building, 3500 Victoria Street, Pittsburgh, PA 15261, USA
4. Department of Orthopedic Surgery, University Hospital of Bern, Freiburgstraß 1, 3000 Bern, Switzerland