Machinery used to provide artificial ventilation. Also called a respirator or life-support machine, it is an electric pump linked to a supply of air which it pumps into the patient through an endotracheal tube passed through the nose or mouth into the trachea (see ENDOTRACHEAL INTUBATION). Sometimes the air is pumped straight into the trachea through an artificial hole called a TRACHEOSTOMY. During ventilation, the patient's BLOOD GASES (oxygen, carbon dioxide and level of acidity) are closely monitored and other bodily activities such as pulse and heart pressure are regularly measured. In order to ensure that ventilation is adequate. Some patients need to be kept on a ventilator for several days, or even weeks, if their medical condition is serious. (See also ARTIFICIAL VENTILATION OF THE LUNGS.)