An apparatus for mechanically ventilating a patient is provided to have two separate components movably arranged with respect to one another within a flexible, air-tight covering fit about the torso of a patient. When the components move away from one another within the air-tight covering, negative pressure is generated which causes the patient to draw air into the lungs. Conversely, when the components stop moving away from one another within the air-tight covering, the patients natural exhalation recoil takes over to allow the patient to expel the air from within the patients lungs. A ventilator for helping a patient such as a premature infant breathe when placed in a chamber, is also provided.
