1. Department of Pulmonary and Critical Care Medicine, Hospital Clinic, Barcelona, Spain
2. CIBER Enfermedades Respiratorias (CIBERES), Mallorca, Spain
3. Dipartimento di Scienze Chirurgiche e Diagnostiche Integrate, Universita' degli Studi di Genova, Genova, Italy
4. University of Barcelona, Barcelona, Spain
5. Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain