Nitrogen narcosis
Inert gas narcosis [Nitrogen narcosis] | |
---|---|
Divers breathe a mixture of oxygen, helium and nitrogen for deep dives to avoid the effects of narcosis. A cylinder label shows the maximum operating depth and mixture (oxygen/helium). | |
Specialty | Medical toxicology |
Narcosis while diving (also known as nitrogen narcosis, inert gas narcosis, raptures of the deep, Martini effect) is a reversible alteration in
Except for
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 much beyond 40 m (130 ft) is generally considered outside the scope of recreational diving. To dive at greater depths, as narcosis and oxygen toxicity become critical risk factors, gas mixtures such as trimix or heliox are used. These mixtures prevent or reduce narcosis by replacing some or all of the inert fraction of the breathing gas with non-narcotic helium. There is a synergy between
Classification
Narcosis results from breathing gases under elevated pressure, and may be classified by the principal gas involved. The
Signs and symptoms
Due to its perception-altering effects, the onset of narcosis may be hard to recognize.[7][8] At its most benign, narcosis results in relief of anxiety – a feeling of tranquillity 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.[9] 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.[10]
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
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. This is a rough guide to give new divers a comparison with a situation they may be more familiar with.[15]
Reported signs and symptoms are summarized against typical depths in meters and feet of sea water in the following table, closely adapted from Deeper into Diving by Lippman and Mitchell:[11]
Pressure (bar) | Depth (m) | Depth (ft) | Comments |
---|---|---|---|
1–2 | 0–10 | 0–33 |
|
2–4 | 10–30 | 33–100 |
|
4–6 | 30–50 | 100–165 |
|
6–8 | 50–70 | 165–230 |
|
8–10 | 70–90 | 230–300 |
|
10+ | 90+ | 300+ |
|
Causes
Some components of breathing gases and their relative narcotic potencies:[2][FN 1][3] | |
Gas | Relative narcotic potency |
---|---|
He | 0.045 |
Ne | 0.3 |
H2 | 0.6 |
N2 | 1.0 |
O2 | 1.7 |
Ar | 2.3 |
Kr | 7.1 |
CO2 | 20.0 |
Xe | 25.6 |
The cause of narcosis is related to the increased solubility of gases in body tissues, as a result of the elevated pressures at depth (
A divers' cognition may be affected on dives as shallow as 10 m (33 ft), but the changes are not usually noticeable.[22] 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.[7][21]
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).[7] Most sport scuba training organizations recommend depths of no more than 40 m (130 ft) because of the risk of narcosis.[15] 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.[20][23] 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.[24]
Narcosis has been compared with
Narcosis is known to be additive to even minimal alcohol intoxication.[27][28] Other sedative and analgesic drugs, such as opiate narcotics and benzodiazepines, add to narcosis.[27]
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.
Similar to the mechanism of
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.[16][17][21] 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.[18][34]
Diagnosis and management
The symptoms of narcosis may be caused by other factors during a dive: ear problems causing disorientation or nausea;[35] early signs of oxygen toxicity causing visual disturbances;[36] carbon dioxide toxicity caused by rebreather scrubber malfunction, excessive work of breathing, or inappropriate breathing pattern, or hypothermia causing rapid breathing and shivering.[37] Nevertheless, the presence of any of these symptoms can 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 event of misdiagnosis when another condition is causing the symptoms, the initial management – ascending to a shallower depth – is still beneficial in most cases, as it is also the appropriate response for most of the alternative causes for the symptoms.[8]
The management of inert gas narcosis is usually simply to ascend to shallower depths, where much of the effect disappears within minutes.[38]. Divers carrying multiple gas mixtures will usually switch to a mixture with more helium before significant narcosis is noticeable during descent. In the event of complications or other conditions being present, ascending remains the correct initial response unless it would violate decompression obligations. Should problems persist, it may be necessary to abort the dive. The decompression schedule can and should still be followed unless other conditions require emergency assistance.[39]
Inert gas narcosis can follow a gas switch to a
Prevention
The most straightforward way to avoid nitrogen narcosis is for a diver to limit the depth of dives. The other main preventive measure is properly informed selection/choice of which gas to use for the particular dive under consideration.
Since narcosis becomes more severe as depth increases, a diver keeping to shallower depths can avoid serious narcosis. Most recreational training agencies will only certify entry level divers to depths of 18 to 20 m (60 to 70 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 management. 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.[41][FN 2] Scuba organizations that train for diving beyond recreational depths,[FN 3] may exclude diving with gases that cause too much narcosis at depth in the average diver (such as the typical widely used nitrox mixtures used for most recreational diving), 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 effect.[2][42] The use of these gases is considered to be technical diving and requires further training and certification.[15]
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.[38]
Deep dives should be made only after a gradual work-up to test the individual diver's sensitivity to increasing depths, taking note of reactions. Scientific evidence does not show that a diver can develop a resistance to the effects of narcosis at a given depth or become tolerant of it.[43]
Because of similar and additive effects, divers should avoid sedating medications and drugs, such as cannabis and alcohol before any dive. A hangover, combined with the reduced physical capacity that goes with it, makes nitrogen narcosis more likely.[27] Experts recommend total abstinence from alcohol for at least 12 hours before diving, and longer for other drugs.[49]
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.[7][21] Nevertheless, the severity of narcosis is unpredictable and it can be fatal while diving, as the result of inappropriate behavior in a dangerous environment.[21]
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
History
French researcher
In 1939,
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.[60] 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,[61] but this hypothesis has been challenged by more recent work.[62][63][64]
A study on the effects of the environment on inert gas narcosis published by Lafère et al. in 2016 concluded that pressure and gas composition may be the only significant external factors influencing inert gas narcosis. It also found that the onset of narcosis follows a short period of raised alertness during descent, and some of the effects persist for at least 30 minutes after the dive.[65][66] As of about 2020, research using
See also
- Equivalent narcotic depth – Method for comparing the narcotic effects of a mixed diving gas with air
- Hydrogen narcosis – Psychotropic state induced by breathing hydrogen at high partial pressures
- Hypercapnia – Abnormally high tissue carbon dioxide levels
- Oxygen toxicity – Toxic effects of breathing oxygen at high partial pressures
- Substance-induced psychosis – Mental condition attributed to substance intoxication
Footnotes
- ^ Value for Krypton from 4th Edition, p. 176.
- ^ A number of technical diving agencies, such as TDI and IANTD teach "extended range" or "deep air" courses which teach diving to depths of up to 55 m (180 ft) without helium.
- ^ BSAC, SAA and other European training agencies teach recreational diving to a depth limit of 50 m (160 ft).
References
Notes
- ^ Askitopoulou, Helen; Ramoutsaki, Ioanna A; Konsolaki, Eleni (April 12, 2000). "Etymology and Literary History of Related Greek Words". Analgesia and Anesthesia. 91 (2). International Anesthesia Research Society: 486–491. Archived from the original on 2021-02-25. Retrieved 2010-06-09.
- ^ a b c d e Bennett & Rostain (2003), p. 305.
- ^ a b Bauer, Ralph W.; Way, Robert O. (1970). "Relative narcotic potencies of hydrogen, helium, nitrogen, and their mixtures". Archived from the original on 2016-07-01. Retrieved 2012-08-01.
- ^ a b Mitchell, Simon (20–22 April 2023). Developments in CO2 monitoring. Rebreather Forum 4. Valetta, Malta. Archived from the original on 16 April 2024. Retrieved 16 April 2024 – via GUE.
- ^ PMID 734806. Archived from the original on July 31, 2009. Retrieved 2009-07-29.)
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- ^ a b c d e f g Bennett & Rostain (2003), p. 301.
- PMID 18619113. Archived from the original on April 15, 2013. Retrieved 2009-08-07.)
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- ^ a b Lippmann & Mitchell (2005), p. 105.
- ^ ISBN 978-0-915539-10-9.
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- ^ ISBN 1-878663-01-1.
- ^ a b Bennett & Rostain (2003), p. 308.
- ^ a b Paton, William (1975). "Diver narcosis, from man to cell membrane". Journal of the South Pacific Underwater Medicine Society (First Published at Oceans 2000 Conference). 5 (2). Archived from the original on April 15, 2013. Retrieved 2008-12-23.
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- ^ a b Bennett & Rostain (2003), p. 303.
- ^ a b c d e Hamilton, R.W.; Kizer, K.W., eds. (1985). "Nitrogen Narcosis". 29th Undersea and Hyperbaric Medical Society Workshop (UHMS Publication Number 64WS(NN)4-26-85). Bethesda, MD: Undersea and Hyperbaric Medical Society. Archived from the original on August 20, 2008. Retrieved 2008-12-23.
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- ^ PSAI Philippines. "Professional Scuba Association International History". Professional Scuba Association International – Philippines. Archived from the original on 2009-01-01. Retrieved 2008-10-31.
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- ^ Lippmann & Mitchell (2005), pp. 110–3.
- ^ PMID 3775969. Archived from the original on October 7, 2008. Retrieved 2008-12-23.)
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- ^ Bennett & Rostain (2003), p. 304.
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- ^ a b Lippmann & Mitchell (2005), p. 106.
- ISBN 978-0-941332-70-5. Archivedfrom the original on 2024-04-16. Retrieved 2023-05-05.
- ^ "Extended Range Diver". International Training. 2009. Archived from the original on 2013-09-12. Retrieved 2013-01-24.
- ^ Hamilton Jr, R.W.; Schreiner, H.R., eds. (1975). "Development of Decompression Procedures for Depths in Excess of 400 feet". 9th Undersea and Hyperbaric Medical Society Workshop (UHMS Publication Number WS2–28–76). Bethesda, MD: Undersea and Hyperbaric Medical Society: 272. Archived from the original on August 20, 2008. Retrieved 2008-12-23.
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- IANTD (January 1, 2009). "IANTD Scuba & CCR, PSCR & SCR Rebreather Diver Programs (Recreational Trimix Diver)". IANTD. Archived from the originalon April 2, 2009. Retrieved 2009-03-22.
- ^ "Mixed-Gas & Oxygen". NOAA Diving Manual, Diving for Science and Technology. 4th. National Oceanic and Atmospheric Administration. 2002.
[16.3.1.2.4] ... since oxygen has some narcotic properties, it is appropriate to include the oxygen in the END calculation when using trimixes (Lambersten et al. 1977,1978). The non-helium portion (i.e., the sum of the oxygen and the nitrogen) is to be regarded as having the same narcotic potency as an equivalent partial pressure of nitrogen in air, regardless of the proportions of oxygen and nitrogen.
- ^ Anttila, Matti (2000). "Narcotic factors of gases". Archived from the original on 2013-12-09. Retrieved 2008-06-10.
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- ^ Lippmann & Mitchell (2005), pp. 430–1.
- ^ St Leger Dowse, Marguerite (2008). "Diving Officer's Conference presentations". British Sub-Aqua Club. Archived from the original on 2011-06-14. Retrieved 2009-08-16.
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: CS1 maint: unfit URL (link - ^ Bennett & Rostain (2003), p. 300.
- ^ Junod, Victor T. (1834). "Recherches physiologiques et thérapeutiques sur les effets de la compression et de la raréfaction de l'air". Revue médicale française et étrangère: Journal des progrès de la médecine hippocratique. Chez Gabon et compagnie: 350–68. Retrieved 2009-06-04.
- ^ Bennett & Rostain (2003), p. 306.
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- ^ Overton, Charles Ernest (1901). "Studien Über Die Narkose". Allgemeiner Pharmakologie (in German). Institut für Pharmakologie.
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- ^ Lambertsen, Christian J.; Gelfand, R.; Clark, J.M. (1978). "University of Pennsylvania Institute for Environmental Medicine report, 1978". University of Pennsylvania. Institute for Environmental Medicine. Archived from the original on June 12, 2010. Retrieved 2009-03-22.
- ^ a b Vrijdag, Xavier (1 February 2023). "Is Oxygen Narcosis A Thing?". gue.com. Archived from the original on 30 March 2023. Retrieved 30 March 2023.
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- ^ Menduno, Michael (14 May 2020). "Measuring Inert Gas Narcosis". alertdiver.eu. DAN Europe. Archived from the original on 30 March 2023. Retrieved 4 April 2023.
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Sources
- Bennett, Peter; Rostain, Jean Claude (2003). "Inert Gas Narcosis". In OCLC 51607923.
- Lippmann, John; OCLC 66524750.
- U.S. Navy Supervisor of Diving (2008). U.S. Navy Diving Manual (PDF). SS521-AG-PRO-010, revision 6. U.S. Naval Sea Systems Command. Archived from the original (PDF) on 2014-12-10. Retrieved 2014-01-21.
External links
- Undersea and Hyperbaric Medical Society Scientific body, publications about nitrogen narcosis.
- Diving Diseases Research Centre (DDRC) UK charity dedicated to treatment of diving diseases.
- Campbell, Ernest S. (2009-06-25). "Diving While Using Marijuana". Retrieved 2009-08-25. ScubaDoc's overview of marijuana and diving.
- Campbell, Ernest S. (2009-05-03). "Alcohol and Diving". Archived from the original on 2007-04-30. Retrieved 2009-08-25. ScubaDoc's overview of alcohol and diving.
- Campbell, George D. (2009-02-01). "Nitrogen Narcosis". Diving with Deep-Six. Retrieved 2009-08-25.