Oxygen: The odorless gas that is present in the air and necessary to maintain life. Oxygen may be given in a medical setting, either to reduce the volume of other gases in the blood or as a vehicle for delivering anesthetics in gas form. It can be delivered via nasal tubes, an oxygen mask, or an oxygen tent. Patients with lung disease or damage may need to use portable oxygen devices on a temporary or permanent basis.
Last Editorial Review: 5/13/2016