[1] Hosp Clin Barcelona, IDIBAPS, Thorax Inst, Barcelona, Spain
[2] CIBER Enfermedades Resp CIBERES, FISIB Palma Mallorca, Palma de Mallorca, Spain
[3] Hosp Univ Miguel Servet, CIBER Enfermedades Resp CIBERES, Inst Aragones Ciencias Salud, Zaragoza, Spain
[4] CIBER Enfermedades Resp CIBERES, Zaragoza, Spain
[5] Hosp Arnau Vilanova, Inst Rec Biomed, Lleida, Spain
[6] Univ Gothenburg, Sahlgrenska Acad, Dept Sleep Med, Gothenburg, Sweden
[7] Univ Roma Tor Vergata, Dept Internal Med, Unit Resp Clin Pharmacol, Rome, Italy
[8] Pulm & Crit Care Med Ctr, Omaha, NE USA