[1] Univ Nova Lisboa, NOVA Med Sch, P-1300 Lisbon, Portugal
[2] Hosp Sao Francisco Xavier CHLO, Dept Intens Care, P-1449 Lisbon, Portugal
[3] Reg Hlth Author Lisbon & Tagus Valley, Pulmol Diagnost Ctr Dr Ribeiro Sanches, Publ Hlth Dept, P-1700 Lisbon, Portugal
[4] OUH Odense Univ Hosp, Ctr Clin Epidemiol & Res Unit Clin Epidemiol, DK-5000 Odense, Denmark