Nitrogen Narcosis

Considering this blog is called ‘Narked Scuba’ I feel that this post is long overdue! What the hell is nitrogen narcosis and how does it affect us? Patience people. All will be revealed.

Firstly I’d like to open with a statement from Jacques Cousteau:

“I am personally quite receptive to nitrogen rapture. I like it and fear it like doom. It destroys instincts of life. Tough individuals are not overcome as soon as neurasthenic persons like me, but they have difficulty extricating themselves. Intellectuals get drunk early and suffer acute attacks on all the senses, which demand hard fighting to overcome”…

So don’t feel too bad about going a bit loopy considering the big man struggled too ūüėÄ

It was first discovered in 1835 that individuals exposed to hyperbaric air behaved as if drunk. Nowadays we know that ALL divers breathing air over 30m will experience some form of narcosis.

So what is Narcosis? It’s defined as a¬†reversible¬†alteration in consciousness that occurs while diving. The greek word¬†őĹőĪŌĀőļŌČŌÉőĻŌā (narcosis) is derived from ‘narke’ which is a term used by Hippocretes and and Homer meaning ‘temporary¬†decline or loss of senses and movement or numbness’. Many people liken it to being drunk or on nitrous oxide gas.

So how does it manifest itself? There are many signs and symptoms of nitrogen narcosis however it¬†doesn’t¬†effect everyone the same. Different things happen to different people at different depths. Most people experience something at depths exceeding 30m.

Here’s a handy table to¬†summarise¬†the rough distribution of effect in depth bands.

  • Mild impairment or performance of unpracticed tasks.
  • Mildly impaired reasoning
  • Mild euphoria possible
  • Delayed response to auditory and visual stimuli
  • Reasoning and immediate memory affected more than motor co-ordination.
  • Calculation error and wrong choices
  • Idea fixation
  • Over confidence and sense of well being
  • Laughter and loquacity (in chambers) which maybe overcome by self control
  • Anxiety (common in cold murky water)


  • Sleepiness, confusion, impaired judgement
  • Hallucinations
  • Severe delay in response to signals, instruction and stimuli.
  • Occasional dizziness
  • Uncontrolled laughter/hysteria (chamber).
  • Terror
  • Poor concentration and mental confusion
  • Stupefaction with some decrease in dexterity and judgement
  • Loss of memory and increased excitability
90m +(300 ft+)
  • Hallucinations
  • sense of impending doom
  • Increased intensity of vision and hearing
  • Sense of impending blackout, euphoria, dizziness, manic or depressive states, sense of levitation, disorganisation of the sense of time
  • Unconsciousness
  • Death

Blimey! Quite the list then, although few of us will ever get deeper than 40m recreationally (unless your tec). However there are a few possible symptoms that cause a real threat to the recreational diver. Delayed response it a biggie. If an¬†emergency¬†occurs, every second counts. If we spend our time pondering the best course of action where we would normally spring into action…accidents will occur.

Great, we know the signs and symptoms but what actually happens to us to cause narcosis?

Unfortunately¬†anaesthetic gases still remain a bit of a mystery but doesn’t stop us having a stab at the mechanisms we think are unfolding when narcosis occurs.

It’s thought that narcosis is related to the solubility of gases in tissues as a result of¬†elevated¬†pressure at depth. More specifically, Nitrogen is especially¬†soluble¬†in fat (lipids) and nerve cells contain a high level of fat and many modern theory hypothesis that nitrogen dissolving into the lipid bilayer of cell membranes cause narcosis. This is thought to change the width or encourage alteration in another physical configuration which consequently interfers with the transmission of impulses along or between neurones.

The reticular centre of the brain receives impulses from throughout the body and sends them to there respective areas in the brain to be processed. The neurons in the reticular centre seem to be especially sensitive to the effect of narcotic agents.

So if the reticular centre is functioning properly then brain function becomes interrupted and is true more so for the alertness and coordination centres.

All this being said, I’d rather not have this happen to me at all! So how do¬†I¬†avoid this?

There are several factors that increase the effect of nitrogen narcoses. Some of these are:

  • Anxiety, apprehension or inexperience
  • Cold water
  • rapid descent
  • excess carbon dioxide
  • reduced sensory input (e.g. poor¬†visibility)
  • fatigue, increase effort or work
  • recent intake of alcohol or certain drugs (e.g. sedatives, hallucinogens and some antihistamines)

There are some things you can do to reduce the effect of narcosis (obviously try to avoid the list above) but more specifically:

  • Strong motivation to perform a task
  • Focused effort on task at hand
  • Reducing partial pressure of nitrogen in breathing gas (e.g. Nitrox)

So it seems to me that its a mind over matter job. Some divers claim to never have been ‘narked’ however it is important to realise that we all feel the effect below 30m. Like a drunk driver who feels perfectly capable of driving safely although tests would show impaired coordination and dulled senses and the driver may not be aware of this debility due to alcohol.

So what if you are diving and you do notice that maybe its taking you a bit longer than normal to read that gauge or you buddy starts grabbing for imaginary fish? Luckly its simple. Ascend to a shallower depth as less pressure means that nitrogen will start to come out of tissues hopefully lessening the effect of narcosis.

There you have it friends. So now when you read me saying ‘stay narked’ your realise I’m getting at the euphoric state rather than the sense of impending doom or terror states ūüėČ

Stay narked!






Copyright (c) <a href=’’>123RF Stock Photos</a>



One response to “Nitrogen Narcosis

  1. Pingback: Gases you should know: Nitrogen | Narked Scuba·

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