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Encyclopedia > Nitrogen narcosis
Nitrogen narcosis [inert gas narcosis]
Classification & external resources
DiseasesDB 30088
MeSH C21.613.455.571

Nitrogen narcosis or inert gas narcosis is a reversible alteration in consciousness producing a state similar to alcohol intoxication in scuba divers at depth. It occurs to some small extent at any depth, but in most cases doesn't become noticeable until deeper depths, usually from 30 to 40 meters. Jacques Cousteau famously described it as the "rapture of the deep". Its precise mechanism is not well understood, but it appears to be a direct effect of nitrogen dissolving into nerve membranes and causing temporary and reversible disruption nerve transmission. While the effect was first observed with nitrogen (in air), other gases including argon, krypton, and hydrogen also cause very similar effects under higher than atmopheric pressure. Nitrous oxide (laughing gas) appears to exert its effect by this mechanism. The Disease Bold textDatabase is a free website that provides information about the relationships between medical conditions, symptoms, and medications. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... Consciousness is a quality of the mind generally regarded to comprise qualities such as subjectivity, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and ones environment. ... Functional group of an alcohol molecule. ... Scuba diving is swimming underwater while using self-contained breathing equipment. ... Jacques-Yves Cousteau in 1976. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18, 3, p Appearance colorless Standard atomic weight 39. ... General Name, Symbol, Number krypton, Kr, 36 Chemical series noble gases Group, Period, Block 18, 4, p Appearance colorless Standard atomic weight 83. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... R-phrases S-phrases Supplementary data page Structure and properties n, εr, etc. ...


The noble gases argon, krypton, and xenon are more anesthetic than nitrogen at a given pressure, and xenon has so much anesthetic activity that it is actually a usable anaesthetic at 80% concentration and normal atmospheric pressure. (Xenon has historically been too expensive to be used very much in practice, but xenon has been sucessfully used for surgical operations, and xenon anesthesia systems are still being proposed and designed). General Name, Symbol, Number xenon, Xe, 54 Chemical series noble gases Group, Period, Block 18, 5, p Appearance colorless Standard atomic weight 131. ...


Due to its perception-altering effects, the onset of nitrogen narcosis may be hard to recognize, its severity is unpredictable, and in scuba diving it can be fatal, as the result of illogical behaviour in a dangerous environment or in extreme cases from its own toxic effect[citation needed]. However, the cure for nitrogen narcosis is a simple one, as effects disappear within minutes upon ascending to shallower depths.

Contents

Effects

Along with the bends, which is a risk during the ascent of a dive, narcosis is one of the most dangerous conditions to affect the scuba diver at depth. The most dangerous aspect of narcosis is the loss of decision-making ability, loss of focus, and impaired judgment, multi tasking and coordination. At its most benign, nitrogen narcosis results in relief of anxiety and a feeling of tranquility and mastery of the environment. These effects are similar to both alcohol and familiar benzodiazepine drugs such as Valium (diazepam) and Xanax (alprazolam). Such effects are not harmful unless there are immediate dangers to be dealt with, and often they are not recognized. Decompression sickness (DCS), the diver’s disease, the bends, or caisson disease is the name given to a variety of symptoms suffered by a person exposed to a reduction in the pressure surrounding their body. ... Diazepam, brand names: Valium, Seduxen, in Europe Apozepam, is a 1,4-benzodiazepine derivative, which possesses anxiolytic, anticonvulsant, sedative and skeletal muscle relaxant properties. ... Alprazolam, is an anxiolytic benzodiazepine used to treat anxiety disorders. ...


When more serious the diver may begin to feel invulnerable, disregarding normal safe diving practices. Other effects include vertigo, tingling and numbness of the lips, mouth and fingers, and extreme exhaustion. Paradoxially, badly affected divers may panic, sometimes remaining on the bottom, too exhausted to ascend. The syndrome may cause exhilaration, giddiness, extreme anxiety, depression, or paranoia, depending on the individual diver and the diver's medical or personal history. An early effect may be loss of near-visual accommodation, causing increased difficulty in close-accommodation reading of small numbers in middle-aged or older divers who already have any degree of presbyopia. Vertigo, a specific type of dizziness, is a major symptom of a balance disorder. ... For other senses of this word, see paranoia (disambiguation). ... Presbyopia (Greek word presbyteros (πρεσβύτερος), meaning elder) is the eyes diminished ability to focus that occurs with aging. ...


Tests have shown that all divers are affected by nitrogen narcosis, though some are less affected than others. Even though it is possible that some divers can cope better than others because of acclimation, training, or special breathing techniques, some effects remain. As with alcohol, these effects are particularly dangerous because even for the same diver, they are not perfectly reproducable at the same depth. Acclimation is a change occurring in an individual as a result to prolonged exposure of a particular environmental condition, such as a horse shedding its winter coat to produce a lighter summer coat. ...


Risk factors

When breathing air, serious impairment due to narcosis starts at depths of about 30 metres (100 feet) or a nitrogen partial pressure of 3.2 bar. At depths of 90 metres (300 feet) or nitrogen partial pressure of 8 bar nitrogen narcosis leads to hallucinations and unconsciousness. The metre (American English:meter) is a measure of length. ... A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′ – a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ... In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. ... The bar (symbol bar), decibar (symbol dbar) and the millibar (symbol mbar, also mb) are units of pressure. ... In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. ...


Although narcosis is most commonly reported below 30 meters, it may be that the divers' cognition is affected before that, but that they are unaware of the changes. Even so there is no reliable method to predict the severity of the effect on an individual diver, and as noted the effect may vary from dive to dive (even on the same day).


Nitrogen 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. Excellent cardiovascular health is no protection and poor health is not necessarily a predictor. Thermal cold, stress, heavy work, fatigue, and carbon dioxide retention all increase the risk and severity of nitrogen narcosis. Nitrogen 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 which last into a day of abstinence from use). Other sedative and analgesic drugs, such as opiate narcotics and benzodiazepines, add to nitrogen narcosis. Altitude sickness, also known as acute mountain sickness (AMS) or altitude illness is a pathological condition that is caused by acute exposure to high altitudes. ... In medical terms, stress is the disruption of homeostasis through physical or psychological stimuli. ... Cannabis, (also known as marijuana, [1] reefer, pot, weed, grass, or ganja [2] in its herbal form and hashish in its resinous form[3]) is a psychoactive product of the plant Cannabis sativa L. subsp. ...


Mechanism

One of the important factors leading to its occurrence seems to be the vertical speed of the diver's descent. Pressure increases as the diver descends, but nitrogen dissolves more slowly than other gases in blood. The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin in Canberra, Australia. ...


Similar to the mechanism of alcohol's effect, this change may cause altered permeability properties of neural cell lipid bilayers. The Meyer-Overton hypothesis states that narcosis happens when the gas penetrates the lipids of the brain's nerve cells. Here it apparently interferes with the transmission of signals from one nerve cell to another. Functional group of an alcohol molecule. ... A polyunsaturated triglyceride. ... Minimum alveolar concentration or MAC is a concept anaesthetists use to compare the strengths of anaesthetic vapours; in simple terms, it is defined as the minimal concentration of the vapour in the lungs that is needed to prevent physical response to a noxious stimulus in 50% of subjects. ... A polyunsaturated triglyceride. ...


The relation of depth to narcosis is informally known as "Martini's law": It's like one martini per 10 meters below 20 meters. This is a very rough guide, which can never be a substitute for the real diving safety rules. Professional divers never suggest such calculation attempts, stressing instead that deep dives can be made only after a gradual training to increasing depths, and always with a linear vertical speed, other diving organisations such as GUE claim that a diver can never train to overcome narcosis, the same way as you can not train to not get drunk when drinking. Instead, they ban diving with gases that cause too high narcosis levels at depth, and use trimix instead. The martini is a cocktail made with gin and dry white vermouth. ... Global Underwater Explorers are a SCUBA diving organization. ... Trimix is a breathing gas, consisting of oxygen, helium and nitrogen, and is often used in deep commercial diving and during the deep phase of dives carried out using Technical diving techniques. ...


The mechanism of the narcosis is related to the solubility of nitrogen in the blood occurring at elevated atmospheric pressures. Once it leaves the tank and enters the diver's lungs it will have the same pressure as the surrounding water, the ambient pressure. Although some experienced divers recommend a constant vertical speed, avoiding sudden changes of inclination which would cause an irregular solution of gas in blood due to a "delay" of pressures adapting, this is not supported by scientific evidence. General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... Human respiratory system Image:Heart-and-hullumgitwalitshnit shmulkelungs. ...


Mitigation

Some diving organisations teach their divers to frequently check their mental state while immersed using the "thumbs test". The two companions regularly show each other their fingers. One shows a number of fingers (e.g. 2), and then the other must respond by showing back one more or one less (i.e. 3 or 1), depending on previous agreement. If either of them botches the arithmetic, they should suspect narcosis.


Because of similar and additive effects, divers should avoid sedating medications and drugs, such as marijuana and alcohol before any dive. In addition to dehydration increasing the risk for decompression illness, a hangover, combined with the reduced physical capacity that goes with it, makes nitrogen narcosis more likely. Experts recommend total abstinence from alcohol at least 24 hours before diving, and longer for heavy drinking. Abstinence time needed for marijuana is unknown, but due 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. Cannabis, (also known as marijuana, [1] reefer, pot, weed, grass, or ganja [2] in its herbal form and hashish in its resinous form[3]) is a psychoactive product of the plant Cannabis sativa L. subsp. ... Functional group of an alcohol molecule. ... Cannabis, (also known as marijuana, [1] reefer, pot, weed, grass, or ganja [2] in its herbal form and hashish in its resinous form[3]) is a psychoactive product of the plant Cannabis sativa L. subsp. ...


Avoidance and cure

The most straightforward way to avoid nitrogen narcosis is for a diver to limit the depth of dives. If narcosis does occur, the effects disappear almost immediately upon ascending to a shallower depth. As narcosis gets worse with increasing depth, a diver keeping to shallower depths can avoid serious narcosis. Most recreational dive schools will only certify basic divers to depths of 18 metres (60 feet), and at these depths narcosis does not present a large risk.


The second most straightforward way to avoid narcosis is to use gasses that limit or exclude nitrogen like trimix for deeper dives.


Specialist training is normally required for certification up to 30 metres (100 feet) on air, and this training should include a discussion of narcosis, its effects, and cure. Some diver training agencies offer speciality training to prepare recreational divers to go to depths of 40 metres (130 ft), often consisting of further theory and some practice in deep dives with close supervision. This page lists SCUBA diver training organizations. ...


While the individual diver often 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 much more predicable and personal. For example, one diver may have trouble with eye focus (close accomodation 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 which their exhaled bubbles make, becomes different. Specialist training may help divers in identifying these personal onset signs, and these may then be used as a signal to ascend to shallower depths. Although it is sometimes true that narcosis interfers with judgement to prevent such decisions, this is by no means always the case.


Other gases

Breathing gases such as trimix and heliox are used in technical diving to reduce nitrogen narcosis by replacing a portion of nitrogen in the gas mixture with helium, thus reducing the partial pressure of nitrogen at depth. Air is the most common and only natural breathing gas. ... Trimix is a breathing gas, consisting of oxygen, helium and nitrogen, and is often used in deep commercial diving and during the deep phase of dives carried out using Technical diving techniques. ... Heliox is a gas that is composed of a mixture of helium (He) and oxygen (O2). ... Technical diving is a form of SCUBA diving that exceeds the scope of recreational diving. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Standard atomic weight 4. ...


Equivalent air depth is a commonly used way of expressing the narcotic effect of different breathing gases. Standard tables list conversion factors for narcotic effect: for example, neon at a fixed pressure has a narcotic effect equivalent to nitrogen at 0.23 times the pressure, so in principle it should be usable at four times the depth. Some gases have other dangerous effects when breathed at pressure; for example, high-pressure oxygen can lead to oxygen toxicity. Helium is the least intoxicating of the breathing gases, but it can cause high pressure nervous syndrome, a still-mysterious but apparently unrelated phenomenon. In technical diving, the equivalent air depth (EAD) is a way of expressing the narcotic effect of breathing gases such as trimix and heliox. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... Oxygen toxicity or oxygen toxicity syndrome is severe hyperoxia caused by breathing oxygen at elevated partial pressures. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Standard atomic weight 4. ... HPNS, High Pressure Nervous Syndrome or Helium Tremors is a diving disorder caused by using breathing gases that contain helium at depths in excess of 130 metres / 429 feet. ...


Inert gas narcosis is only one factor which influences the choice of gas mixture; the risk of decompression sickness and oxygen toxicity, cost, and other factors are also important. Decompression sickness (DCS), the diver’s disease, the bends, or caisson disease is the name given to a variety of symptoms suffered by a person exposed to a reduction in the pressure surrounding their body. ... Oxygen toxicity or oxygen toxicity syndrome is severe hyperoxia caused by breathing oxygen at elevated partial pressures. ...


References

  • Nitrogen Narcosis from Diving with deep-six by George D. Campbell, III. (viewed 10 April 2005)
  • Exotic diving gases by Matti Anttila. (viewed 10 April 2005)
  • [1] from Investigating the relationship between simulated depth, cognitive function and metacognitive awareness by Sam Harding. (viewed 20 December 2006)

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External links


  Results from FactBites:
 
Nitrogen Narcosis | AHealthyMe.com (675 words)
Nitrogen narcosis, commonly referred to as "rapture of the deep," typically becomes noticeable at 100 ft underwater and is incapacitating at 300 ft, causing stupor, blindness, unconsciousness, and even death.
Nitrogen narcosis is caused by gases in the body acting in a manner described by Dalton's Law of partial pressures: the total pressure of a gas mixture is equal to the sum of the partial pressures of gases in the mixture.
Nitrogen narcosis may be differentiated from toxicity of oxygen, carbon monoxide, or carbon dioxide by the absence of such symptoms as headache, seizure, and bluish color of the lips and nail beds.
nitrogen narcosis - definition of nitrogen narcosis in Encyclopedia (986 words)
Nitrogen narcosis is a reversible alteration in consciousness producing a state similar to alcohol intoxication in SCUBA divers at depths beyond 30m.
The mechanism of the narcosis is related to the solubility of nitrogen in the blood occurring at elevated atmospheric pressures.
In technical diving, breathing gases such as trimix and heliox are used to reduce nitrogen nacrosis by replacing a portion of nitrogen in the gas mixture with helium, reducing the partial pressure of nitrogen at depth.
  More results at FactBites »

 
 

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