1 School of Medicine, Unit of Respiratory Diseases, Department of Medical Sciences and Infective Diseases, IRCCS San Matteo Foundation, University of Pavia, Pavia, Italy - g.stella@smatteo.pv.it.
2 School of Medicine, Unit of Respiratory Diseases, Department of Medical Sciences and Infective Diseases, IRCCS San Matteo Foundation, University of Pavia, Pavia, Italy.