<unk>  or<unk>  syndrome (also known as the "Paul Bert effect") is severe hyperoxia caused by breathing<unk>  at elevated partial pressures. The high concentration of<unk>  damages cells. The precise mechanism(s) of the damage are not known, but<unk>  gas has a propensity to react with certain metals to form superoxide which may attack double bonds in many organic systems, including the unsaturated fatty acid residues in cells. High concentrations of<unk>  are known to increase the formation of cascades of such free-radicals in biological systems, at which in many then go on to directly harm DNA and other structures (see nitric oxide, peroxynitrite, and trioxidane). Normally, the body has many defense systems against such damage (see glutathione, catalase, and superoxide dismutase) but at higher concentrations of free<unk> , these systems are eventually overwhelmed with time, and the rate of damage to cell membranes exceeds the capacity of systems which control or repair it. Cell damage and cell death then results.
Oxygen toxicity
Cerebral hypoxia
Carbon monoxide poisoning
Organophosphate poisoning
Mercury poisoning
Lead poisoning
Nitrogen narcosis
Cyanide poisoning