 Materials and Methods Twenty healthy male volunteers aged between 18 and 65 years-old with no history of respiratory or cardiovascular pathologies will be enrolled. Females and all subjects with history of respiratory or cardiovascular diseases will be excluded. Volunteers will be enrolled among staff members of the Cardiac Surgical Intensive Care Unit of the Agostino Gemelli University Hospital in Rome. Each enrolled volunteer will be trained to perform Valsalvas and Mullers maneuvers. 