Narcosis while diving (also known as nitrogen narcosis, inert gas narcosis, raptures of the deep, Martini effect), is a reversible alteration in consciousness that occurs while scuba diving at depth. The Greek word ναρκωσις (narcosis) is derived from narke, "temporary decline or loss of senses and movement, numbness", a term used by Homer and Hippocrates.[2] Narcosis produces a state similar to alcohol intoxication or nitrous oxide inhalation, and can occur during shallow dives, but usually does not become noticeable until greater depths, beyond 30 meters (100 ft).
..Due to its perception-altering effects, the onset of narcosis may be hard to recognize.[6][7] At its most benign, narcosis results in relief of anxiety and a feeling of tranquility and mastery of the environment. These effects are essentially identical to various concentrations of nitrous oxide. They also resemble (though not as closely) the effects of alcohol and the familiar benzodiazepine drugs such as diazepam and alprazolam.[8] Such effects are not harmful unless they cause some immediate danger not to be recognized and addressed. Once stabilized, the effects generally remain the same at a given depth, only worsening if the diver ventures deeper.
..The cause of narcosis is related to the increased solubility of gases in body tissues, as a result of the elevated pressures at depth (Henry's law).[12] Modern theories have suggested that inert gases dissolving in the lipid bilayer of cell membranes cause narcosis.[13] More recently, researchers have been looking at neurotransmitter receptor protein mechanisms as a possible cause of the narcosis.[14] The breathing gas mix entering the diver's lungs will have the same pressure as the surrounding water, known as the ambient pressure. For any given depth, the pressure of gases in the blood passing through the brain catches up with ambient pressure within a minute or two and this produces a delay in narcotic effect after coming to a new depth.