Negative pressure ventilator

A negative pressure ventilator (NPV) is a type of mechanical ventilator that stimulates an ill person's breathing by periodically applying negative air pressure to their body to expand and contract the chest cavity. == Description == In most NPVs (such as the iron lung in the diagram), the negative pressure 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.

Source: Wikipedia — Negative pressure ventilator (CC BY-SA 4.0)