1. Intensive Care Unit, Hospital Universitario Río Hortega, Valladolid, Spain
2. Intensive Care Unit, Hospital Universitario de Burgos, Burgos, Spain
3. Intensive Care Unit, Hospital Clínico Universitario, Valladolid, Spain
4. Intensive Care Unit, Complejo Hospitalario de Salamanca, Salamanca, Spain
5. Intensive Care Unit, Complejo Hospitalario de León, León, Spain
6. Intensive Care Unit, Hospital Río Carrión, Palencia, Spain
7. Intensive Care Unit, Hospital General de Segovia, Segovia, Spain
8. Intensive Care Unit, Hospital El Bierzo, Ponferrada, León, Spain
9. Intensive Care Unit, Complejo Hospitalario de Soria, Soria, Spain
10. Intensive Care Unit, Hospital Virgen de la Concha, Zamora, Spain
11. CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain
12. Multidisciplinary Organ Dysfunction Evaluation Research Network (MODERN), Hospital Universitario Dr Negrin, Las Palmas de Gran Canaria, Spain