Slowed mental activity, as indicated by increased reaction time and increased errors in cognitive function, are effects which increase the risk of a diver mismanaging an incident. When more serious, the diver may feel overconfident, disregarding normal safe diving practices. The syndrome may cause exhilaration, giddiness, extreme anxiety, depression, or paranoia, depending on the individual diver and the diver's medical or personal history.
Other effects include vertigo and visual or auditory disturbances. The most dangerous aspects of narcosis are the impairment of judgement, multi-tasking and coordination, and the loss of decision-making ability and focus. Once stabilized, the effects generally remain the same at a given depth, only worsening if the diver ventures deeper. Such effects are not harmful unless they cause some immediate danger to go unrecognized and unaddressed. They also resemble (though not as closely) the effects of alcohol or cannabis and the familiar benzodiazepine drugs such as diazepam and alprazolam. These effects are essentially identical to various concentrations of nitrous oxide. At its most benign, narcosis results in relief of anxiety – a feeling of tranquillity and mastery of the environment. Narcosis can produce tunnel vision, making it difficult to read multiple gauges.ĭue to its perception-altering effects, the onset of narcosis may be hard to recognize. Xenon has historically been too expensive to be used very much in practice, but it has been successfully used for surgical operations, and xenon anesthesia systems are still being proposed and designed. The noble gases argon, krypton, and xenon are more narcotic than nitrogen at a given pressure, and xenon has so much anesthetic activity that it is a usable anesthetic at 80% concentration and normal atmospheric pressure. The effect of carbon dioxide is a consistent diminution of mental and psychomotor function. The noble gases, except helium and probably neon, as well as nitrogen, oxygen and hydrogen cause a decrement in mental function, but their effect on psychomotor function (processes affecting the coordination of sensory or cognitive processes and motor activity) varies widely. Narcosis results from breathing gases under elevated pressure, and may be classified by the principal gas involved. These mixtures prevent narcosis by replacing some or all of the inert fraction of the breathing gas with non-narcotic helium. In order to dive at greater depths, as narcosis and oxygen toxicity become critical risk factors, specialist training is required in the use of various helium-containing gas mixtures such as trimix or heliox. Diving much beyond 40 m (130 ft) is generally considered outside the scope of recreational diving. Thus narcosis while diving in open water rarely develops into a serious problem as long as the divers are aware of its symptoms, and are able to ascend to manage it. Narcosis may be completely reversed in a few minutes by ascending to a shallower depth, with no long-term effects. The main class of diving that deals with its prevention and treatment is scuba diving at substantial depth. Narcosis can affect all divers, although susceptibility varies widely among individuals and from dive to dive. Divers can learn to cope with some of the effects of narcosis, but it is impossible to develop a tolerance. As depth increases, the mental impairment may become hazardous. The effect is consistently greater for gases with a higher lipid solubility, and although the mechanism of this phenomenon is still not fully clear, there is good evidence that the two properties are mechanistically related. It can occur during shallow dives, but does not usually become noticeable at depths less than 30 meters (100 ft).Įxcept for helium and probably neon, all gases that can be breathed have a narcotic effect, although widely varying in degree. Narcosis produces a state similar to drunkenness (alcohol intoxication), or nitrous oxide inhalation. The Greek word νάρκωσις (narkōsis), "the act of making numb", is derived from νάρκη (narkē), "numbness, torpor", a term used by Homer and Hippocrates. It is caused by the anesthetic effect of certain gases at high pressure. 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 diving at depth. A cylinder label shows the maximum operating depth and mixture (oxygen/helium). Divers breathe a mixture of oxygen, helium and nitrogen for deep dives to avoid the effects of narcosis.
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