Archive for October 29th, 2014

October 29, 2014

Nitrogen Narcosis


Nitrogen narcosis [nahr-koh-sis] (also known as ‘raptures of the deep’ and the ‘Martini effect’) is a reversible alteration in consciousness that occurs while diving at depth. It is caused by the anesthetic effect of certain gases at high pressure. The Greek word ‘narcosis’ is derived from ‘narke,’ ‘temporary decline or loss of senses and movement, numbness,’ a term used by Homer and Hippocrates. Narcosis produces a state similar to intoxication caused by drinking alcohol or inhaling nitrous oxide. It can occur during shallow dives, but usually becomes noticeable at depths greater than 30 meters (100 ft).

Except for helium and probably neon, all gases that can be breathed have a narcotic effect, although widely varying in degree. The effect is consistently greater for gases with a higher lipid solubility (the ability to diffuse directly through the fatty part of a cell membrane), and there is good evidence that the two properties are mechanistically related. As depth increases, the mental impairment may become hazardous. Divers can learn to cope with some of the effects of narcosis, but it is impossible to develop a tolerance. Narcosis affects all divers, although susceptibility varies widely from dive to dive, and between individuals.

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