1. Department of Pneumology, Cologne Merheim Hospital, Cologne, Germany
2. Faculty of Health/School of Medicine, Witten/Herdecke University, Witten, Germany
3. Department of Pulmonary Diseases/Home Mechanical Ventilation, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
4. Groningen Research Institute for Asthma and COPD (GRIAC), University of Groningen, University Medical Center Groningen, Groningen, The Netherlands