1. Respiratory and Critical Care Unit, Policlinico S. Orsola-Malpighi di Bologna, IRCCS Azienda Ospedaliero Universitaria di Bologna, Via Albertoni 15, 40138 Bologna, Italy
2. Department of Medical and Surgical Science (DIMEC), Alma Mater Studiorum University of Bologna, Via Massarenti 9, 40138 Bologna, Italy