1. Respiratory Service, Hospital Universitario de Gran Canaria Dr. Negrín, Canary Islands, Spain
2. Respiratory Service, Hospital Universitario Nuestra Señora de la Candelaria, Canary Islands, Spain
3. Respiratory Service, Hospital Universitario Miguel Servet, Zaragoza, Spain
4. Respiratory Service, Clínica Universitaria de Navarra, Pamplona, Spain
5. Investigation Unit, Hospital Universitario de Gran Canaria Dr. Negrín, Canary Islands, Spain
6. Pulmonary and Critical Care Service, Brigham and Women’s Hospital, Boston, Massachusetts and
7. Pulmonary and Critical Care Division, Baystate Medical Center, Springfield, Massachusetts