Analytic Reviews : Oxygen Toxicity

Abstract

Oxygen therapy is administered to patients to decrease tissue hypoxia and to relieve arterial hypoxemia. High concentrations of oxygen often are used for short pe riods of time in patients with acute respiratory illnesses, and concentrations only slightly higher than ambient levels are administered for much longer time periods to patients with chronic respiratory diseases. Supplying oxygen to plants, animals, or bacteria has long been known to produce varying amounts of tissue damage; toxicity increases as concentrations of oxygen or the pressure used during exposure increases. End-organ damage from hyperoxia depends on both the concentra tion of oxygen administered and the pressure during the exposure. Prolonged exposure to hyperbaric oxygen (> 2.5 atmosphere of pressure) causes both central nervous system and pulmonary toxicity that results in atelectasis, pulmonary edema, and seizures. Lung dam age as a result of normobaric hyperoxia is the predomi nant manifestation of toxicity. A severe retinopathy (re trolental fibroplasia) also can occur in neonates during oxygen exposures at ambient pressure, and cases have been reported to occur with only modest increases in inspired oxygen concentrations. For these reasons, the lowest possible concentration of oxygen that relieves tissue hypoxia is administered to patients, and the oxy gen concentration is stabilized when the desired thera peutic goals are accomplished.