1 University Hospital Zurich, Division of Pulmonology, Raemistrasse 100, 8091 Zurich, Switzerland; University of Zurich, Faculty of Medicine, Raemistrasse 71, 8006 Zurich, Switzerland. Electronic address: rene.hage@usz.ch.
2 University Hospital Zurich, Division of Pulmonology, Raemistrasse 100, 8091 Zurich, Switzerland; University of Zurich, Faculty of Medicine, Raemistrasse 71, 8006 Zurich, Switzerland.