For an inert gas the narcotic potency was found to be proportional to its lipid solubility. As hydrogen has only 0.55 the solubility of nitrogen, deep diving experiments using hydrox were conducted by Arne Zetterström between 1943 and 1945. Jacques-Yves Cousteau in 1953 famously described it as "livresse des grandes profondeurs" or the "rapture of the deep".Further research into the possible mechanisms of narcosis by anesthetic action led to the "minimum alveolar concentration" concept in 1965. This measures the relative concentration of different gases required to prevent motor response in 50% of subjects in response to stimulus, and shows similar results for anesthetic potency as the measurements of lipid solubility. The (NOAA) Diving Manual was revised to recommend treating oxygen as if it were as narcotic as nitrogen, following research by Christian J. Lambertsen et al. in 1977 and 1978. See also
Hydrogen narcosis – Psychotropic state induced by breathing hydrogen at high partial pressures
Oxygen toxicity – Toxic effects of breathing oxygen at high concentrations

Footnotes
References
Notes
Sources
Bennett, Peter; Rostain, Jean Claude (2003). "Inert Gas Narcosis". In Brubakk, Alf O; Neuman, Tom S (eds.). Bennett and Elliotts physiology and medicine of diving (5th ed.). United States: Saunders. ISBN 0-7020-2571-2. OCLC 51607923. Lippmann, John; Mitchell, Simon J. (2005). "Nitrogen narcosis". Deeper into Diving (2nd ed.). Victoria, Australia: J. L. Publications. pp. 103–8. ISBN 0-9752290-1-X. OCLC 66524750. U.S. Navy Supervisor of Diving (2008). U.S. Navy Diving Manual (PDF). SS521-AG-PRO-010, revision 6. U.S. Naval Sea Systems Command. Archived from the original (PDF) on 2014-12-10. Retrieved 2014-01-21.
In the rare event of misdiagnosis when another condition is causing the symptoms, the initial management – ascending closer to the surface – is still essential. Prevention
The most straightforward way to avoid nitrogen narcosis is for a diver to limit the depth of dives. The other main preventive measure is properly informed selection/choice of which gas to use for the particular dive under consideration. Since narcosis becomes more severe as depth increases, a diver keeping to shallower depths can avoid serious narcosis. Most recreational dive schools will only certify entry level divers to depths of 18 to 20 m (60 to 70 ft), and at these depths narcosis does not present a significant risk. Further training is normally required for certification up to 30 m (100 ft) on air, and this training should include a discussion of narcosis, its effects, and management. Some diver training agencies offer specialized training to prepare recreational divers to go to depths of 40 m (130 ft), often consisting of further theory and some practice in deep dives under close supervision. Scuba organizations that train for diving beyond recreational depths, may forbid diving with gases that cause too much narcosis at depth in the average diver (such as the typical widely used nitrox mixtures suitable for most recreational diving), and strongly encourage the use of other breathing gas mixes containing helium in place of some or all of the nitrogen in air – such as trimix and heliox – because helium has no narcotic effect.