Persons at risk:
(1) patient on mechanical ventilation receiving high inspiratory levels of oxygen
(2) patient undergoing hyperbaric therapy
(3) diver breathing high partial pressures of oxygen for prolonged periods
Acute toxicity:
(1) Acute toxicity may occur after exposure to 60-100% oxygen at 1 atmosphere. The duration of exposure required to produce injury varies, but usually it takes > 24 hours. In general, the higher the concentration of oxygen, the shorter the exposure required to produce injury.
(2) Symptoms of tracheobronchitis develop first, with coughing, painful breathing on inspiration and substernal chest pain. These symptoms are reversible if the exposure is discontinued.
(3) With continued exposure, pulmonary edema and acute respiratory distress syndrome (ARDS) may develop.
Chronic toxicity:
(1) In infants prolonged exposure to elevated partial pressures of oxygen may be associated with bronchopulmonary dysplasia.
(2) Interstitial fibrosis may develop.
Additional risk factors for injury:
(1) Patients with protein malnutrition and/or vitamin A or E deficiencies may be more susceptible to oxidation injury.
(2) Certain drugs like bleomycin or disulfiram may potentiate the lung injury.
Diagnosis is based on combinations of the following findings:
(1) an exposure history
(2) clinical symptoms (may not be available if the person is unconscious)
(3) abnormal pulmonary function testing, with decreases in vital capacity, lung compliance and carbon monoxide diffusing capacity.
