A further distinction can be made between routine exposure and exposure required for emergency treatment, where a higher risk of oxygen toxicity may be justified to achieve a reduction of a more critical injury, particularly when in a relatively safe controlled and monitored environment. The Repex (repetitive exposure) method, developed in 1988, allows oxygen toxicity dosage to be calculated using a single dose value equivalent to 1 minute at atmospheric pressure called an Oxygen Tolerance Unit (OTU), is used to avoid toxic effects over several days of operetional exposure. Some dive computers will automatically track the dosage bases on depth and selected gas mixture. The limits allow a greater exposure when the person has not been exposed recently, and daily allowable dose decreases with an increase in consecutive days with exposure. These values may not be fully supported by current data. A more recent proposal uses a simple power equation, Toxicity Index (TI) = t2 × PO2c, where t is time and c is the power term. This was derived from the chemical reactions producing reactive oxygen or nitrogen species, and has been shown to give good predictions for CNS toxicity with c = 6.8 and for pulmonary toxicity for c = 4.57.For pulmonary toxicity, time is in hours, and PO2 in atmospheres absolute, TI should be limited to 250. For CNS toxicity, time is in minutes, PO2 in atmospheres absolute, and a TI of 26,108 indicates a 1% risk.
Treatment
Historically, acute MS was a fatal disease, with death occurring within a year of onset, often secondary to extensive brain stem demyelination. Treatment recommendations, based on anecdotes, include plasma exchange in conjunction with high-dose glucocorticoids(e.g., 1 to 2 g/day of methylprednisolone for 10 days followed by a slow taper). For patients who survive the acute attack, follow-up treatments include immunosuppression (monthly mitoxantrone or cyclophosphamide) either alone or in combination with IFN beta or GA (glatiramer acetate). Prognosis
Marburg variant of MS is an acute fulminant demyelinating process which in most cases progresses inexorably to death within 1–2 years. However, there are some reports of Marburg MS reaching stability by three years. See also
Malignant multiple sclerosis
Tumefactive multiple sclerosis

References


== External links ==