The PEGASO Vent is a negative pressure ventilator and represents the primary and most traditional method of assisted long-term ventilation. The PEGASO Vent withdraws mechanically the air from a chamber, which embraces the chest (or the whole body) and as a consequence creates a sub-atmospheric pressure inside. This leads to an expansion of the chest, which causes a decrease in intrapulmonary pressure, and increases flow of ambient air into the lungs. When the PEGASO Vent switches to positive pressure and forces air in the chamber, the chest will be compressed and the lungs will exhale. The exhalation can also be passive, through ambient instead of positive pressure, which often is sufficient to deflate the lungs. This ventilation method reproduces mechanically ventilation similar to the human spontaneous breathing.