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Nitrogen Narcosis: Symptoms, Causes, and Prevention in Diving

Today we’re talking about the symptoms of nitrogen narcosis, its causes, risk factors, and, above all, its prevention during diving. So that it doesn’t happen to you, and if it does, you know how to act.

You know, when my children were very little and we played hide-and-seek, they thought that by just hiding their heads, I couldn’t see them anymore. That belief of being untouchable by simply closing your eyes is not only held by kids. Sometimes, adults also prefer to close their eyes to avoid seeing what bothers them, as if it would magically disappear.

Yes, we’re talking about nitrogen narcosis, and we’re doing it because we believe it’s necessary. We’ve realized that it’s a topic that is often avoided, not treated rigorously, or considered unimportant. Whether due to lack of knowledge or intent, that strategy serves no purpose other than keeping divers in the dark and therefore lacking the necessary resources to prevent nitrogen narcosis. Today, we’re going to provide you with resources so that nitrogen narcosis doesn’t really worry you, because you know how to act.

1. What is Nitrogen Narcosis?

Narcosis is a physiological phenomenon. We use the term “drugged” when a substance alters our consciousness, often associated with artificial drowsiness. It can also affect neuromuscular function, which refers to the connections between our brain and the muscles, impacting our movement and even perceptions of the environment and our own body.

In the context of diving, the narcotic substance is nitrogen, although it could be any other inert gas (such as argon, krypton, and xenon) if we could breathe them.

If the partial pressure of nitrogen decreases, such as when we ascend, the effects of nitrogen narcosis disappear without consequences. This brings us to a crucial point: nitrogen narcosis itself doesn’t pose a direct health risk, but the impaired decision-making capacity it causes can be hazardous.


2. What Causes Nitrogen Narcosis


2.1. The Chief Cause of Nitrogen Narcosis Is

Divers, who are known for their imagination, have given various names to nitrogen narcosis: deep-sea drunkenness, deep-sea intoxication, and deep-sea ecstasy, Martini Effect. Ok, the last terms in these names aren’t crucial for our discussion.

Let’s focus on the first terms of each. The common element in all these names is depth.

Now, you may wonder, how deep?

Numerous experiments have evaluated the cognitive functions of divers. They were tested on memory, sentence comprehension, and simple calculations at various depths. These tests indicate that the effects of nitrogen narcosis become noticeable at around 30m / 98ft, although the intensity of these effects varies among individuals.

In summary: the main cause of nitrogen narcosis is the behavior of this gas once dissolved in the bloodstream when under pressure. However, it is not the only one.


2.2. Other Causes of Nitrogen Narcosis Related to The Nature of The Gas

It’s important to note that we are specifically focusing on nitrogen narcosis because it is the gas commonly used in diving. However, there are other inert gases that also have narcotic potential. For example, xenon is used in medicine for anesthesia and is effective even at sea level.

On the opposite side, we find helium, which, despite being an inert gas, does not cause narcosis in autonomous diving depths, only at depths exceeding 1000 meters. This is likely why it is used in TRIMIX gas mixes!

So, what exactly does compressed nitrogen do in our bodies that can intoxicate us?

The Meyer and Overton hypothesis (the most widely accepted) considers that the narcotic potential of a gas is determined by its ability to dissolve in fat. Why? Because neurons have a layer of fat that covers them.

As all divers know, pressurized nitrogen dissolves in our body, including that fat. This causes the membrane to thicken, making it difficult for nerve impulses to flow normally. However, it’s important to note that this hypothesis is not fully proven.

Other theories suggest that nitrogen affects neuronal synapses, causing malfunctions in the brain where nerve impulses are no longer transmitted normally.

According to the biochemical theory, narcotic gases affect neurotransmitters, which are the biomolecules responsible for carrying information.

Additionally, the molecular weight of the gas has been considered a possible factor. The higher the molecular weight, the greater the narcotic potency.

Which is the right answer? Probably they all are. We are really talking about a syndrome, which means that there is not a single biological mechanism involved.

Nitrogen Narcosis Symptoms - narcosis de nitrógeno (4)

3. Diving Nitrogen Narcosis Symptoms

The French researcher Victor T. Junod was the first to describe the symptoms of nitrogen narcosis in 1894, noting that ‘the functions of the brain are active, and the imagination is very vivid; thoughts take on a peculiar charm, and in some people, symptoms of intoxication occur.’ There is no doubt that Junod was very poetic, but the truth is that the symptoms of narcosis are quite prosaic.

Next, we will list the symptoms of nitrogen narcosis, but it’s important to note that these symptoms do not always appear simultaneously. Instead, they tend to increase and worsen as you descend to greater depths.

For some individuals, the symptoms of nitrogen narcosis are sudden and consistently occur at specific depths. Others are much more resistant to its effects.

I vividly recall a dive from my deep-diving course with a couple. The man was a stocky, blond Dutchman, and the woman was a short, skinny Korean. At a depth of 34m/111ft, he experienced narcosis. He came to a complete stop and didn’t respond to my OK signals. After ascending a few meters, everything returned to normal. Neither she nor I were affected by the pressure.


3.1. Early Signs of Diving Narcosis

The symptoms observed in nitrogen narcosis initially manifest with alterations in higher cognitive functions, such as:

  • The way in which we understand and judge the environment is altered.
  • Reasoning abilities are affected.
  • The decision-making process is impacted.
  • Effectiveness in actions may decrease.
  • Short-term memory and concentration may be impaired.
  • In addition, the diver may experience an exhilarating sensation similar to what we feel after consuming the first few alcoholic drinks.


3.2. Worsening of Nitrogen Narcosis Symptoms

As the partial pressure of nitrogen in the blood increases with descent to greater depths, deficits in manual dexterity and more pronounced mental impairment may occur. These can include difficulties in focusing on ideas, experiencing hallucinations, and ultimately leading to stupor and disorientation.

rapture of the deep (2)

4. Risk factors of nitrogen narcosis in scuba diving

Why are some people affected by nitrogen narcosis diving to 30 meters, while others reach 40 meters without any issues? It’s because the individual diver is a variable that needs to be considered when examining the symptoms of nitrogen narcosis.

We have discussed inert gases that are not present in diving, but there is one narcotic gas that is present – carbon dioxide (CO2).

Normally, we expel CO2 with our breath without a problem. However, what happens when we over-exert ourselves or encounter a situation that causes anxiety? What if we had been drinking the night before? Or if we start to feel hypothermia?

In these cases, we produce more carbon dioxide. When the partial pressure of CO2 in the blood exceeds 45mm, hypercapnia occurs. This situation involves two narcotic gases acting in your system, increasing the likelihood of nitrogen narcosis.

So, listen to me. If you’re planning a deep dive the next day, save the beers for later, go to bed early, and make sure you’re wearing the right wetsuit for the dive you’re about to undertake.”


5. How to Avoid Scuba Diving Narcosis

While Neptune’s children have reached depths of more than 40 m/131 ft while breathing only compressed air (such as Eduard Admetlla, who achieved a record descent to -100 m/328 ft in the 1950s), it is not possible to avoid nitrogen narcosis. Let me explain: if you descend while breathing a mixture of oxygen and nitrogen, narcosis is bound to occur at one depth or another.

But you might argue that technical divers descend to depths greater than 40 m/131 ft. Yes, they do, but they don’t breathe the same mixture as you do. They use Trimix, which replaces some of the nitrogen with helium. Another mixture they use is Heliox, which contains no nitrogen, only oxygen + helium.

To avoid nitrogen narcosis:

  • Stay above 30m/98ft, and if you go beyond 40m/131ft, use gas mixtures with less nitrogen.
  • Train yourself as a deep diver.
  • Be mindful of potential symptoms of nitrogen narcosis and monitor how you feel during the dive.
  • Take care before a dive: rest, avoid alcohol, and stay well-hydrated.
  • While diving, breathe slowly and avoid excessive physical exertion.
  • Always dive with a partner and keep an eye on each other’s well-being.
  • Choose your equipment wisely for deep dives.
Diving Narcosis

6. Treatment for Scuba Diving Narcosis

Nitrogen narcosis is treated by ascending. It’s that easy. Fortunately, the symptoms of diving narcosis are completely reversible, so if you find your buddy suffering from it, begin your ascent as you would if the dive had ended.

Give your partner time for their body to readapt to the new pressure conditions. When it happens, they won’t even have a hangover. After an episode of nitrogen narcosis, while diving, it is best to end the dive.

It should be noted that treating diving narcosis is easier than detecting it.

Some tests you can do to monitor it:

  1. Check your gauge, and if you suddenly don’t understand what it says, ascend.
  2. If the world appears as if you were looking through a poorly tuned television or a tube, move up.
  3. If you ask your dive buddy something, even something as simple as ‘Are you okay?’, and they do not know how to answer you, you both should ascend.
  4. Deep divers are always attentive to their buddies, and the moment they see a change in behavior, they intervene to avoid the nitrogen narcosis symptoms.