The procedure, usually carried out in an operating theatre or intensive-care unit, in which a device called a VENTILATOR takes over a person's breathing. This is done for someone who is unable to breathe normally. Damage to the respiratory centre of the brain as a result of head injury, disease of the brain, or an overdose of sedative or narcotic drugs may affect the respiratory centre. Chest injuries, disease of the lungs, nerve or muscle disorders or surgery of the chest or abdomen can also affect breathing and require the use of a ventilator to maintain normal breathing. Artificial ventilation can also be carried out as an emergency by mouth-to-mouth resuscitation. (See also ANAESTHESIA; ARTIFICIAL VENTILATION OF THE LUNGS.)