A medical ventilator (or simply ventilator in context) is a machine designed to mechanically move breathable air into and out of the lungs, to provide the mechanism of breathing for a patient who is physically unable to breathe, or breathing insufficiently.While modern ventilators are computerized machines, patients can be ventilated with a bag valve mask, a simple hand-operated bag-valve mask.Ventilators are chiefly used in intensive care medicine, home care, and emergency medicine (as standalone units) and in anesthesia (as a component of an anesthesia machine).Medical ventilators are sometimes colloquially called "respirators," a term which stems from commonly used devices in the 1950s (particularly the "Bird Respirator").