Anyone who has taken an advanced scuba course is familiar with the term “nitrogen narcosis,” but what exactly does it mean, and how can it affect you?

If you’re thinking of exploring beyond the open-water certification depth of 60 feet (18 m), you will need additional training. The advanced open water course or something similar is the natural next step. A key component of these courses involves becoming acquainted with narcosis so that you can safely dive to 130 feet (40 m), which is the depth limit for recreational dives. If you’re already a qualified deep diver, you may have forgotten some of what you were taught about narcosis. So depending on your level, here’s an introduction or a refresher on what narcosis is, how it affects you, and how you can reduce its effects.

What is Nitrogen Narcosis?

Narcosis comes from the Greek word “narke,” which loosely translates as “numb.” People have given narcosis all sorts of names over the years, with perhaps the best known description coming from Jacques Cousteau himself; he aptly named it “rapture of the deep.”

But whether you call it nitrogen narcosis, inert gas narcosis or just plain gas narcosis (oxygen is as narcotic as nitrogen), it is caused by the increased partial pressure of gases we breathe while diving, and for recreational diving that means nitrogen. A higher partial pressure means that more gas can dissolve into our tissues (remember Henry’s law). As nitrogen dissolves in the fat tissues in the nerve cells of our brains, it can disrupt the transmission of signals to and from the brain. This can affect you in numerous ways during a dive.

You or your buddy may feel euphoric and find everything pretty amusing all of a sudden. This is usually accompanied by absentmindedness, which doesn’t go well with monitoring your instruments. Conversely, you may feel a little paranoid and end up obsessively checking your SPG and watch your buddy like a hawk. Paranoia is usually accompanied by feelings of anxiety, which can get worse if not properly managed.

Regardless of your behavior, your brain is slower; your ability to undertake simple tasks is impaired; your reaction times are reduced; and your coordination, memory, and judgment are all affected.  The deeper you go, the worse it gets. This is one reason why we have depth and time-at-depth limits while recreational diving.

How to Deal with Nitrogen Narcosis

The first step in dealing with narcosis is to recognize how it impacts you.

Other things you can do include:

  • Get plenty of rest and stay hydrated, before and after diving. If you’re tired, your brain is slower, and narcosis will only make this worse.
  • Avoid alcohol. It really doesn’t mix with diving, and narcosis is no different.
  • Build up to doing deeper dives and do them regularly. You cannot build up a tolerance to narcosis, but you can learn to cope with its effects through gradual and regular exposure.
  • Avoid overexertion before descending, and also throughout the dive. CO2 buildup can increase narcosis (and CO2 is narcotic too).
  • Descend slowly and allow that partial pressure to increase gradually. You might even want to pause every 33 feet (10 m) on the way down for 10 to 30 seconds.
  • Get warm and stay warm. Being cold has been shown to increase the narcotic hit.
  • Try to avoid task loading by keeping things simple. Use a slate with pre-prepared phrases written on it.
  • Ensure you are well practiced with your diving skills, especially emergency skills.
  • Never be afraid to call the dive.

The easiest way to get rid of narcosis is to reduce the partial pressure of the gas by simply ascending to a shallower depth; the euphoric or absentminded feelings should immediately diminish or disappear entirely. For most divers, the effects of narcosis at 100 feet (30 m) are easily dealt with, but that doesn’t mean we should be complacent. Just because you didn’t feel “narced” today doesn’t mean you won’t feel it tomorrow — nitrogen narcosis will affect you in different ways on different days.

Finally, don’t be the diver who wants to see how “narced” he can get. This is a sure-fire way to get yourself, and possibly others, into trouble. Treat narcosis as the enemy, and always try to minimize its effects and stay within your comfort zone.

Richard Devanney is a PADI, SSI, BSAC and SDI instructor who teaches technical diving through TDI, SSI XR and PADI TecRec. He currently lives in Reykjavik, Iceland, and manages Dive Silfra, owned by parent company Arctic Adventures. He runs a Facebook technical diving page called Iceland Technical Diving. Contact him at richard@adventures.is or rdevanney@gmail.com.

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