Editing Nitrogen narcosis (section)

== Causes ==
{| class="wikitable floatright" style="width:17.5em; margin-top:-0.5em;"
|+Some components of breathing gases and their relative narcotic potencies{{sfnp|Bennett|Rostain|2003|p=305}}{{r |Krypton|group=FN}}{{r |Bauer1970}}
|-
! scope="col" | Gas
! scope="col" | Relative narcotic potency
|-
| [[Helium|He]] || style="padding-left:2em;" | 0.045
|-
| [[Neon|Ne]] ||  style="padding-left:2em;" | 0.3
|-
| [[Hydrogen|H<sub>2</sub>]] || style="padding-left:2em;" | 0.6
|-
| [[Nitrogen|N<sub>2</sub>]] || style="padding-left:2em;" | 1.0
|-
| [[Oxygen|O<sub>2</sub>]] || style="padding-left:2em;" | 1.7
|-
| [[Argon|Ar]] || style="padding-left:2em;" | 2.3
|-
| [[Krypton|Kr]] || style="padding-left:2em;" | 7.1
|-
| [[Carbon dioxide|CO<sub>2</sub>]] || style="padding-left:1.5em;" | 20.0
|-
| [[Xenon|Xe]] || style="padding-left:1.5em;" | 25.6
|}
{{Main|Theories of general anaesthetic action}}

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]]).{{sfnp|Bennett|Rostain|2003|p=308}} It has been suggested that inert gases dissolving in the [[lipid bilayer]] of [[cell membrane]]s cause narcosis.{{r |Paton1975}} More recently, researchers have been looking at [[neurotransmitter receptor]] protein mechanisms as a possible cause of narcosis.{{r |Rostain2006}} The breathing gas mix entering the diver's [[human lung|lung]]s will have the same pressure as the surrounding water, known as the [[ambient pressure]]. After a change of depth, the partial pressure of inert gases in the blood passing through the brain catches up with ambient pressure within a minute or two, which results in a delayed change in narcotic effect after descending to a new depth.{{sfnp|Bennett|Rostain|2003|p=301}}{{r |CaseHaldane1941}} Rapid compression potentiates narcosis owing to [[carbon dioxide retention]].{{sfnp|Bennett|Rostain|2003|p=303}}{{r |Hamilton1985}}

A divers' [[cognition]] may be affected on dives as shallow as {{convert|10|m|ft|abbr=on}}, but the changes are not usually noticeable.{{r |Petri2003}} 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.{{sfnp|Bennett|Rostain|2003|p=301}}{{r |Hamilton1985}}

Significant impairment due to narcosis is an increasing risk below depths of about {{convert|30|m|ft|sigfig=1|abbr=on}}, corresponding to an ambient pressure of about {{convert|4|bar|lk=in|abbr=on}}.{{sfnp|Bennett|Rostain|2003|p=301}} Most sport scuba training organizations recommend depths of no more than {{convert|40|m|ft|abbr=on}} because of the risk of narcosis.{{r |Brylske2006}} When breathing air at depths of {{convert|90|m|ft|abbr=on}}&nbsp;– an ambient pressure of about {{convert|10|bar|abbr=on}}&nbsp;– narcosis in most divers leads to hallucinations, loss of memory, and unconsciousness.{{sfnp|Bennett|Rostain|2003|p=303}}{{r |Hill1933}} A number of divers have died in attempts to set air depth records below {{convert|120|m|ft|abbr=on|sigfig=1}}. Because of these incidents, ''[[Guinness World Records]]'' no longer reports on this figure.{{r |psai}}

Narcosis has been compared with [[altitude sickness]] regarding its variability of onset (though not its symptoms); its effects depend on many factors, with variations between individuals. Thermal cold, [[stress (medicine)|stress]], heavy work, fatigue, and carbon dioxide retention all increase the risk and severity of narcosis.{{r |Hesser1978}}{{sfnp|Bennett|Rostain|2003|p=301}} Carbon dioxide has a high narcotic potential and also causes increased blood flow to the brain, increasing the effects of other gases.{{r |Kety1948}} Increased risk of narcosis results from increasing the amount of carbon dioxide retained through heavy exercise, shallow or [[skip breathing]], high [[work of breathing]], or because of poor gas exchange in the lungs.{{sfnp|Lippmann|Mitchell|2005|pp=110–3}}<ref name="Mitchell 2024" />

Narcosis is known to be additive to even minimal alcohol intoxication.{{r |Fowler1986 |Michalodimitrakis1987}} Other [[sedative]] and [[analgesic]] drugs, such as [[opiate]] narcotics and benzodiazepines, add to narcosis.{{r |Fowler1986}}