[1] Sao Francisco Xavier Hosp, CHLO, Polyvalent Intens Care Unit, Lisbon, Portugal
[2] Univ Nova Lisboa, CEDOC, Fac Med Sci, Lisbon, Portugal
[3] Univ Porto, Fac Med, CINTESIS, Dept Biostat & Med Informat, P-4100 Oporto, Portugal
[4] Santo Antonio Hosp, Oporto, Portugal