oxygen (O) /ok″səjən/ [Gk, oxys, sharp, genein, to produce] , a tasteless, odorless, colorless gas essential for human respiration and metabolism. Its atomic number is 8; its atomic mass is 15.9994. Oxygen makes up approximately 21% of the gases in the atmosphere. In anesthesia, oxygen functions as a carrier gas for the delivery of anesthetic agents to tissues. In respiratory therapy, oxygen is administered to increase the amount circulating in the blood. Overdose of oxygen can cause irreversible toxicity in people with pulmonary abnormalities, especially when complicated by chronic carbon dioxide retention. Prolonged administration of high concentrations of oxygen may cause irreversible retinal damage to infants’ eyes. An oxygen-rich environment is favorable to fire and explosion. Thus smoking, open flame, or electric spark must be avoided when oxygen is being administered. See also oxygen toxicity.
