1. Respiratory Department, San Pedro de Alcántara Hospital, Cáceres, Spain
2. CIBER de Enfermedades Respiratorias (CIBERES), Madrid, Spain
3. Instituto Universitario de Investigación Biosanitaria de Extremadura (INUBE), Badajoz, Spain
4. Medicine/Pulmonary and Critical Care, University of Chicago, Chicago, Illinois
5. Institut de Recerca Biomédica de Lleida (IRBLLEIDA), Lleida, Spain
6. Respiratory Department, Virgen del Puerto Hospital, Plasencia, Cáceres, Spain
7. Unidad Médico-Quirúrgica de Enfermedades Respiratorias, Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/Universidad de Sevilla, Sevilla, Spain
8. Respiratory Department, University Hospital, Burgos, Spain
9. Respiratory Department, IIS Fundación Jiménez Díaz, Madrid, Spain
10. Respiratory Department, Valdecilla Hospital, Santander, Spain
11. Respiratory Department, Gregorio Marañon Hospital, Madrid, Spain
12. Respiratory Department, Miguel Servet Hospital, Zaragoza, Spain
13. Respiratory Department, Valld'Hebron Hospital, Barcelona, Spain
14. Respiratory Department, Doce de Octubre Hospital, Madrid, Spain
15. Respiratory Department, San Juan Hospital, Alicante, Spain
16. Respiratory Department, Alava University Hospital IRB, Vitoria, Spain
17. Nursing Department, Extremadura University, Cáceres, Spain; and
18. Department of Quantitative Methods, University of Las Palmas de Gran Canaria, Las Palmas, Spain