Oxygen Toxicity occurs when excessive oxygen inhalation is done as in prolonged ventilation with hundred percent (100%) oxygen.
When the inspired oxygen saturation or FiO2 of a patient on oxygen therapy is kept for long time Toxicity of oxygen is bound can take place. FiO2 of 100 % should not be kept for more than 12 hours. Similarly within 24 hours of oxygen therapy with FiO2 of 90%, it should be lowered to 80%.
Systemic Effects of Oxygen Toxicity
Pulmonary Toxicity
Prolonged high concentrations can cause pulmonary toxicity. 100% oxygen is usually considered safe for up to 8 to 12 hours in normal adults (in infants and neonates 100% oxygen for more than 2 to 3 hours can cause pulmonary toxicity). Oxygen Toxicity depends on alveolar concentration (not on arterial concentration).
Pathophysiology: Toxicity with oxygen is because of toxic radicals of oxygen like superoxide and hydroxyl ions, singlet oxygen, hydrogen peroxide. These radicals damage the capillary membrane increasing capillary permeability and ARDS like picture.
Abnormality in ciliary transport, absorption atelectasis and tracheobronchitis are other features of oxygen toxicity.
In neonates pulmonary toxicity manifests as bronchopulmonary dysplasia.
Retrolental Fibroplasia
This is dependent on arterial oxygen concentration. Premature neonates (< 36 weeks) are at greatest risk.
Cerebral Effects
Acute oxygen toxicity may manifest as convulsions this is called as Paul Bert effect. The convulsions in Paul Bert effect have to be managed by anticonvulsants.