1 Department of Clinical and Experimental Medicine, University of Catania, 95131 Catania, Italy.
2 Respiratory Medicine Unit, Policlinico "G. Rodolico-San Marco" University Hospital, Via S. Sofia, 78, 95123 Catania, Italy.
3 Department of Surgical, Oncological and Oral Science (Di.Chir.On.S.), University of Palermo, 90127 Palermo, Italy.
4 Department of Anesthesia, Intensive Care and Emergency, Policlinico Paolo Giaccone, University of Palermo, Via del Vespro, 129, 90127 Palermo, Italy.