1 Department of Pediatric Pneumology, University Children's Hospital Basel (UKBB), Basel, Switzerland Division of Respiratory Medicine, Department of Pediatrics, University Children's Hospital of Bern, Bern, Switzerland.
2 Department of Pediatric Pneumology, University Children's Hospital of Ruhr University Bochum at St Josef-Hospital, Bochum, Germany.
3 Division of Respiratory Medicine, Department of Pediatrics, University Children's Hospital of Bern, Bern, Switzerland.