[1] Hosp Univ Getafe, Unidad Cuidados Intens, Madrid 28905, Spain
[2] Univ Toronto, Univ Hlth Network, Dept Med, Div Respirol, Toronto, ON, Canada
[3] Univ Toronto, Univ Hlth Network, Interdepartmental Div Crit Care Med, Toronto, ON, Canada
[4] King Fahad Natl Guard Hosp, Riyadh, Saudi Arabia
[5] Hosp Prof Posadas, Buenos Aires, DF, Argentina
[6] Hosp Gen Medellin, Medellin, Colombia
[7] Tufts Univ, Sch Med, New England Med Ctr, Dept Med,Pulm & Crit Care Div, Boston, MA 02111 USA
[8] Fdn S Maugeri, Ist Sci Pavia, Resp Intens Care Unit, Pavia, Italy
[9] Hosp Univ Sao Jose, Belo Horizonte, MG, Brazil
[10] Hosp Clin, Caracas, Venezuela
[11] Univ Texas, Hlth Sci Ctr, San Antonio, TX USA