Iron lung cylinder (black), patient head exposed through sealed opening. Diaphragm (yellow) mechanically extends, and then retracts, varying cylinder air<unk>  and causing the patient's chest to expand (top), and then contract (bottom) In most NPVs (such as the iron lung in the diagram), the<unk><unk>  is applied to the patient's torso, or entire body below the neck, to cause their chest to expand, expanding their lungs, drawing air into the patient's lungs through their airway, assisting (or forcing) inhalation. When<unk><unk>  is released, the chest naturally contracts, compressing the lungs, causing exhalation. In some cases, positive external<unk>  may be applied to the torso to further stimulate exhalation. Another form of NPV device (such as the Pulmotor) is placed at the patient's airway, and alternates<unk><unk>  with positive<unk>  to pump air into their lungs (inhale under positive<unk> , then suck it back out (exhale under<unk><unk> .
Negative pressure ventilator
Mechanical ventilation
Artificial ventilation
Elastomeric respirator
Pressure support ventilation
Positive airway pressure
Non-invasive ventilation
Airway pressure release ventilation