text: nitrogen narcosis 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 . it is caused by the anesthetic effect of certain gases at high pressure . the greek word ( narcosis ) is derived from , " temporary decline or loss of senses and movement , numbness " , a term used by homer and hippocrates . narcosis produces a state similar to drunkenness ( alcohol intoxication ) , or nitrous oxide inhalation . it can occur during shallow dives , but does not usually become noticeable at depths less 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 , 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 . narcosis may be completely reversed in a few minutes by ascending to a shallower depth , with no long - term effects . 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 . diving beyond 40 m ( 130 ft ) is generally considered outside the scope of recreational diving . below these 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 . these mixtures prevent narcosis by replacing some of the breathing gas with non - narcotic helium . classification narcosis results from breathing gases under elevated pressure , and may be classified by the principal gas involved . 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 . the effects of carbon dioxide consistently result in a diminution of mental and psychomotor function . 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 . 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 . signs and symptoms due to its perception - altering effects , the onset of narcosis may be hard to recognize . at its most benign , narcosis results in relief of anxiety – 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 or marijuana and the familiar benzodiazepine drugs such as diazepam and alprazolam . such effects are not harmful unless they cause some immediate danger to go unrecognized and unaddressed . once stabilized , the effects generally remain the same at a given depth , only worsening if the diver ventures deeper . the most dangerous aspects of narcosis are the impairment of judgement , multi - tasking and coordination , and the loss of decision - making ability and focus . other effects include vertigo and visual or auditory disturbances . the syndrome may cause exhilaration , giddiness , extreme anxiety , depression , or paranoia , depending on the individual diver and the diver 's medical or personal history . when more serious , the diver may feel overconfident , disregarding normal safe diving practices . the relation of depth to narcosis is sometimes informally known as " martini 's law " , the idea that narcosis results in the feeling of one martini for every 10 m ( 33 ft ) below 20 m ( 66 ft ) depth . professional divers use such a calculation only as a rough guide to give new divers a metaphor , comparing a situation they may be more familiar with . reported signs and symptoms are summarized against typical depths in meters and feet of sea water in the following table : causes 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 ) . modern theories have suggested that inert gases dissolving in the lipid bilayer of cell membranes cause narcosis . more recently , researchers have been looking at neurotransmitter receptor protein mechanisms as a possible cause of narcosis . the breathing gas mix entering the diver 's lungs will have the same pressure as the surrounding water , known as the ambient pressure . after any change of depth , the pressure of gases in the blood passing through the brain catches up with ambient pressure within a minute or two , which results in a delayed narcotic effect after descending to a new depth . rapid compression potentiates narcosis owing to carbon dioxide retention . a divers ' cognition may be affected on dives as shallow as 10 m ( 33 ft ) , but the changes are not usually noticeable . there is no reliable method to predict the depth at which narcosis becomes noticeable , or the severity of the effect on an individual diver , as it may vary from dive to dive even on the same day . significant impairment due to narcosis is an increasing risk below depths of about 30 m ( 100 ft ) , corresponding to an ambient pressure of about 4 bar ( 400 kpa ) . most sport scuba training organizations recommend depths of no more than 40 m ( 130 ft ) because of the risk of narcosis . when breathing air at depths of 90 m ( 300 ft ) – an ambient pressure of about 10 bar ( 1 , 000 kpa ) – narcosis in most divers leads to hallucinations , loss of memory , and unconsciousness . a number of divers have died in attempts to set air depth records below 120 m ( 400 ft ) . because of these incidents , guinness world records no longer reports on this figure . narcosis has been compared with altitude sickness insofar as its variability ( though not its symptoms ) ; its effects depend on many factors , with variations between individuals . thermal cold , stress , heavy work , fatigue , and carbon dioxide retention all increase the risk and severity of narcosis . carbon dioxide has a high narcotic potential and also causes increased blood flow to the brain , increasing the effects of other gases . increased risk of narcosis results from increasing the amount of carbon dioxide retained through heavy exercise , shallow or skip breathing , or because of poor gas exchange in the lungs . narcosis is known to be additive to even minimal alcohol intoxication , and also to the effects of other drugs such as marijuana ( which is more likely than alcohol to have effects that last into a day of abstinence from use ) . other sedative and analgesic drugs , such as opiate narcotics and benzodiazepines , add to narcosis . mechanism the precise mechanism is not well understood , but it appears to be the direct effect of gas dissolving into nerve membranes and causing temporary disruption in nerve transmissions . while the effect was first observed with air , other gases including argon , krypton and hydrogen cause very similar effects at higher than atmospheric pressure . some of these effects may be due to antagonism at nmda receptors and potentiation of gabaa receptors , similar to the mechanism of nonpolar anesthetics such diethyl ether or ethylene . however , their reproduction by the very chemically inactive gas argon makes them unlikely to be a strictly chemical bonding to receptors in the usual sense of a chemical bond . an indirect physical effect – such as a change in membrane volume – would therefore be needed to affect the ligand - gated ion channels of nerve cells . et al. have suggested non - chemical binding due to the attractive van der waals force between proteins and inert gases . similar to the mechanism of ethanol 's effect , the increase of gas dissolved in nerve cell membranes may cause altered ion permeability properties of the neural cells ' lipid bilayers . the partial pressure of a gas required to cause a measured degree of impairment correlates well with the lipid solubility of the gas : the greater the solubility , the less partial pressure is needed . an early theory , the meyer - overton hypothesis , suggested that narcosis happens when the gas penetrates the lipids of the brain 's nerve cells , causing direct mechanical interference with the transmission of signals from one nerve cell to another . more recently , specific types of chemically gated receptors in nerve cells have been identified as being involved with anesthesia and narcosis . however , the basic and most general underlying idea , that nerve transmission is altered in many diffuse areas of the brain as a result of gas molecules dissolved in the nerve cells ' fatty membranes , remains largely unchallenged . management and diagnosis the management of narcosis is simply to ascend to shallower depths ; the effects then disappear within minutes . in the event of complications or other conditions being present , ascending is always the correct initial response . should problems remain , then it is necessary to abort the dive . the decompression schedule can still be followed unless other conditions require emergency assistance . the symptoms of narcosis may be caused by other factors during a dive : ear problems causing disorientation or nausea ; early signs of oxygen toxicity causing visual disturbances ; or hypothermia causing rapid breathing and shivering . nevertheless , the presence of any of these symptoms should imply narcosis . alleviation of the effects upon ascending to a shallower depth will confirm the diagnosis . given the setting , other likely conditions do not produce reversible effects . 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 . 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 basic divers to depths of 18 m ( 60 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 cure . 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 , 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 potential . the use of these gases forms part of technical diving and requires further training and certification . while the individual diver cannot predict exactly at what depth the onset of narcosis will occur on a given day , the first symptoms of narcosis for any given diver are often more predictable and personal . for example , one diver may have trouble with eye focus ( close accommodation for middle - aged divers ) , another may experience feelings of euphoria , and another feelings of claustrophobia . some divers report that they have hearing changes , and that the sound their exhaled bubbles make becomes different . specialist training may help divers to identify these personal onset signs , which may then be used as a signal to ascend to avoid the narcosis , although severe narcosis may interfere with the judgement necessary to take preventive action . deep dives should be made only after a gradual training to test the individual diver 's sensitivity to increasing depths , with careful supervision and logging of reactions . diving organizations such as global underwater explorers ( ) emphasize that such sessions are for the purpose of gaining experience in recognizing the onset symptoms of narcosis for an individual , which are somewhat more repeatable than for the average group of divers . scientific evidence does not show that a diver can train to overcome any measure of narcosis at a given depth or become tolerant of it . equivalent narcotic depth ( end ) is a commonly used way of expressing the narcotic effect of different breathing gases . the national oceanic and atmospheric administration ( noaa ) diving manual now states that oxygen and nitrogen should be considered equally narcotic . standard tables , based on relative lipid solubilities , list conversion factors for narcotic effect of other gases . for example , hydrogen at a given pressure has a narcotic effect equivalent to nitrogen at 0 . 55 times that pressure , so in principle it should be usable at more than twice the depth . argon , however , has 2 . 33 times the narcotic effect of nitrogen , and is a poor choice as a breathing gas for diving ( it is used as a drysuit inflation gas , owing to its low thermal conductivity ) . some gases have other dangerous effects when breathed at pressure ; for example , high - pressure oxygen can lead to oxygen toxicity . although helium is the least intoxicating of the breathing gases , at greater depths it can cause high pressure nervous syndrome , a still mysterious but apparently unrelated phenomenon . inert gas narcosis is only one factor influencing the choice of gas mixture ; the risks of decompression sickness and oxygen toxicity , cost , and other factors are also important . because of similar and additive effects , divers should avoid sedating medications and drugs , such as marijuana and alcohol before any dive . a hangover , combined with the reduced physical capacity that goes with it , makes nitrogen narcosis more likely . experts recommend total abstinence from alcohol for at least 12 hours before diving , and longer for other drugs . abstinence time needed for marijuana is unknown , but owing to the much longer half - life of the active agent of this drug in the body , it is likely to be longer than for alcohol . prognosis and epidemiology narcosis is potentially one of the most dangerous conditions to affect the scuba diver below about 30 m ( 100 ft ) . except for occasional amnesia of events at depth , the effects of narcosis are entirely removed on ascent and therefore pose no problem in themselves , even for repeated , chronic or acute exposure . nevertheless , the severity of narcosis is unpredictable and it can be fatal while diving , as the result of illogical behavior in a dangerous environment . tests have shown that all divers are affected by nitrogen narcosis , though some experience lesser effects than others . even though it is possible that some divers can manage better than others because of learning to cope with the subjective impairment , the underlying behavioral effects remain . these effects are particularly dangerous because a diver may feel they are not experiencing narcosis , yet still be affected by it . history french researcher victor t. junod was the first to describe symptoms of narcosis in 1834 , noting " the functions of the brain are activated , imagination is lively , thoughts have a peculiar charm and , in some persons , symptoms of intoxication are present . " junod suggested that narcosis resulted from pressure causing increased blood flow and hence stimulating nerve centers . walter moxon ( 1836 – 1886 ) , a prominent victorian physician , hypothesized in 1881 that pressure forced blood to inaccessible parts of the body and the stagnant blood then resulted in emotional changes . the first report of anesthetic potency being related to lipid solubility was published by hans h. meyer in 1899 , entitled zur theorie der . two years later a similar theory was published independently by charles ernest overton . what became known as the meyer - overton hypothesis may be illustrated by a graph comparing narcotic potency with solubility in oil . in 1939 , albert r. behnke and o. d. yarborough demonstrated that gases other than nitrogen also could cause narcosis . 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 were conducted by arne between 1943 and 1945 . jacques - yves cousteau in 1953 famously described it as " l ’ des grandes " 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 .