[1] Univ Roma La Sapienza, Dept Anesthesiol & Intens Care, Rome, Italy
[2] Univ Roma La Sapienza, Dept Cardiovasc & Resp Sci, Rome, Italy
[3] Univ Paris 11, Hop Bicetre, Serv Reanimat Med, Le Kremlin Bicetre, France
[4] UCL, Bloomsbury Inst Intens Care, London, England
[5] Univ Cattolica Sacro Cuore, Dept Anesthesiol & Intens Care, Rome, Italy
[6] Univ Roma La Sapienza, Dept Internal Med, Rome, Italy
[7] Tufts Univ, New England Med Ctr, Boston, MA 02111 USA