[1] Hacettepe Univ, Fac Med, Med Intens Care Unit, TR-06100 Ankara, Turkey
[2] US Dept Vet Affairs, Vet Affairs Edward Hines Jr Hosp, Div Pulm & Crit Care Med, Hines, IL 60141 USA
[3] Loyola Univ, Stritch Sch Med, Hines, IL USA
[4] Hacettepe Univ, Fac Med, Dept Publ Hlth, TR-06100 Ankara, Turkey