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Oxygen (O2) is toxic at elevated partial pressures and oxygen toxicity can therefore occur whenever the O2 partial pressure is substantially elevated for more than a few hours. Oxygen toxicity is a diving disorder and also a potential complication of mechanical ventilation.
In the context of diving, O2 toxicity can be caused by breathing any breathing gas at high pressure, for example, when underwater at depth.
In humans, there are several types of oxygen toxicity:
- Central nervous system oxygen toxicity is caused by breathing gas mixes at elevated partial pressures, 1.0 bar or more, of oxygen even for periods of 2 or more hours. At high partial pressures of oxygen, 1.6 bar or more, the dangerous exposure period could be seconds or minutes. The diver suffers a fit similar to an epileptic fit, which although not lethal in itself, can have other lethal consequences if it occurs underwater - for example, drowning or pressure damage resulting from rapid ascent to the surface.
- Pulmonary oxygen toxicity is caused by extended exposure, 16 or more hours, to moderate partial pressures, 0.5 bar or more, of oxygen and can lead to irreversible lung damage. This is a rare complication in diving, but may be a relevant cause of morbidity in intensive care patients undergoing mechanical ventilation.
- ''Retinopathy of prematurity
