1. Respiratory Department, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
2. Respiratory Department, Hospital Universitario 12 de Octubre, Madrid, Spain
3. School of Medicine, Complutense University, Madrid, Spain
4. Respiratory Department, Hospital Universitario de Getafe, Getafe, Madrid, Spain
5. Respiratory Department, La Fe University and Polytechnic Hospital, Valencia, Spain
6. Respiratory Department, Hospital Universitari de Bellvitge, Barcelona, Spain