[1] Univ Florence, Dept Crit Care Med & Surg Gerontol & Geriatr Med, Intens Care Unit, I-50141 Florence, Italy
[2] AOU Careggi, I-50141 Florence, Italy
[3] Univ Florence, Dept Crit Care Med & Surg, Internal Med & Cardiol Unit, I-50141 Florence, Italy
[4] Columbia Univ Coll Phys & Surg, Div Pulm Allergy & Crit Care Med, New York, NY 10032 USA