A ventilator is a machine that helps a person breathe or breathes for the person. It controls and monitors the amounts of air and oxygen that flows into the person's lungs. Ventilators may be used for people who have serious breathing conditions. These include conditions such as acute respiratory distress syndrome (ARDS), asthma, chronic obstructive pulmonary disease (COPD), or severe pneumonia.

Doctors usually attach a ventilator to a tube they have placed into the person's windpipe (trachea) through the mouth or nose. If the person needs the ventilator for a long period of time, the doctor may make an opening directly in the trachea (tracheostomy) and place the tube through this opening.