Central nervous system toxicity may be referred to as the "Paul Bert effect".Pulmonary oxygen toxicity was first described by J. Lorrain Smith in 1899 when he noted central nervous system toxicity and discovered in experiments in mice and birds that 0.43 bar (43 kPa) had no effect but 0.75 bar (75 kPa) of oxygen was a pulmonary irritant. Pulmonary toxicity may be referred to as the "Lorrain Smith effect". The first recorded human exposure was undertaken in 1910 by Bornstein when two men breathed oxygen at 2.8 bar (280 kPa) for 30 minutes, while he went on to 48 minutes with no symptoms. In 1912, Bornstein developed cramps in his hands and legs while breathing oxygen at 2.8 bar (280 kPa) for 51 minutes. Smith then went on to show that intermittent exposure to a breathing gas with less oxygen permitted the lungs to recover and delayed the onset of pulmonary toxicity.Albert R. Behnke et al. in 1935 were the first to observe visual field contraction (tunnel vision) on dives between 1.0 bar (100 kPa) and 4.1 bar (410 kPa). During World War II, Donald and Yarbrough et al. performed over 2,000 experiments on oxygen toxicity to support the initial use of closed circuit oxygen rebreathers. Naval divers in the early years of oxygen rebreather diving developed a mythology about a monster called "Oxygen Pete", who lurked in the bottom of the Admiralty Experimental Diving Unit "wet pot" (a water-filled hyperbaric chamber) to catch unwary divers.
Central nervous system toxicity
Exposures, from minutes to a few hours, to partial pressures of oxygen above 1.6 bars (160 kPa)—about eight times normal atmospheric partial pressure—are usually associated with central nervous system oxygen toxicity and are most likely to occur among patients undergoing hyperbaric oxygen therapy and divers. Since sea level atmospheric pressure is about 1 bar (100 kPa), central nervous system toxicity can only occur under hyperbaric conditions, where ambient pressure is above normal. Divers breathing air at depths beyond 60 m (200 ft) face an increasing risk of an oxygen toxicity "hit" (seizure). Divers breathing a gas mixture enriched with oxygen, such as nitrox, can similarly have a seizure at shallower depths, should they descend below the maximum operating depth allowed for the mixture. Lung toxicity
The lungs and the remainder of the respiratory tract are exposed to the highest concentration of oxygen in the human body and are therefore the first organs to show toxicity. Pulmonary toxicity occurs only with exposure to partial pressures of oxygen greater than 0.5 bar (50 kPa), corresponding to an oxygen fraction of 50% at normal atmospheric pressure.