.: 2010

The common term for nitrogen narcosis used in the scuba diving fraternity is the “raptures of the deep”. Another common term is a scuba diver suffering this condition is said to be “narked”.

What is Nitrogen Narcosis?
Nitrogen narcosis is a condition in scuba diving where a scuba diver has feelings of elation and euphoria. It is similar to being slightly intoxicated with alcohol, or from having nitrous oxide when undergoing certain medical procedures such as dental work.

Because of this impact of a scuba diver feeling invincible and reduced anxiety underwater, the condition has the potential to be extremely dangerous. Some divers have been known to take their regulator from their mouth; while other have lost all awareness of depth and simply continued swimming down to greater depths and into greater trouble.

Nitrogen narcosis usually occurs at depths greater than 30 metres. However, the condition can affect some scuba divers at a lesser depth.

The symptoms reduce as the diver ascends to shallower depths.

What Causes Nitrogen Narcosis?
Nitrogen narcosis is caused by the impact of nitrogen in the body.

A scuba diver breathes a normal mix of air from a scuba tank. This air contains around 79% nitrogen.

When breathed at depth the partial pressure of the nitrogen results in more nitrogen in the body. However, as nitrogen is an inert gas it doesn’t react with the body’s blood and tissues.
Because the nitrogen doesn’t react chemically with the body, it is considered that the nitrogen affects the signals that are sent along the nerve fibres in the body. This results in the impact being mainly related to brain and nerve functions.

Signs and Symptoms of Nitrogen Narcosis
Nitrogen narcosis affects scuba divers in different ways. The following are some of the reported signs and symptoms impacting the cognitive function of a scuba diver with nitrogen narcosis:

General feelings of euphoria
Feelings of elation
A sense of well-being
Over confidence
Laughter
Light-headedness
Loss of decision making ability
Memory problems.

Physical symptoms of a scuba diver with nitrogen narcosis can be:
Vertigo
Tunnel vision
Impaired coordination and concentration
Tingling or numbness in the body’s extremities.

The biggest problem with these symptoms is that a scuba diver suffering from some of the above symptoms of nitrogen narcosis may not be able to recognise that they have the symptom.
For example, a scuba diver suffering with a sensation of over-confidence and euphoria may not be able to think that there is something wrong because these are “good” type sensations. The loss of decision-making ability is obviously a serious problem if a scuba diver has to calculate decompression times underwater.

Problems can so easily occur when a scuba diver has these feelings of extreme confidence. They can go off and do things underwater that they wouldn’t normally do.

Scuba Diving’s Martini Law and Nitrogen Narcosis
In the diving fraternity, the impact of nitrogen narcosis in relation to depth is known as “Martini’s Law”. This is roughly based on the analogy that for each 10 metres in depth, the effect is like consuming one martini. At 30 metres, a scuba diver may feel like they have drunk three martinis.

This is a very rough guide only and should not be relied on to predict the onset of nitrogen narcosis

How Scuba Divers Can Prevent Nitrogen Narcosis
The onset of nitrogen narcosis is directly related to depth. The deeper the scuba diver goes, the greater the impact of nitrogen narcosis.

It is almost impossible to predict the depth that symptoms may start showing as nitrogen narcosis impacts each scuba diver differently. And the impact can vary from each scuba dive.

There are many variable such as cold, stress, fatigue. It is even thought that nitrogen narcosis may be worse depending on the amount of alcohol or some drugs that may have been taken into the body a few days earlier.

The best way to prevent nitrogen narcosis is to be aware of the possibility of narcosis occurring, and then if it does the scuba diver should immediately ascend to a shallower depth.
Scuba diving buddies should always be on the lookout for signs of nitrogen narcosis; especially on a deep dive over 25 metres.

The problem of nitrogen narcosis can best be addressed by the following:
using a good scuba dive plan
implementing good scuba diving practices
keeping mentally and physically healthy
a good relationship and understanding between scuba dive buddies
keeping in shallow depths.

Nitrogen narcosis should not be something that is treated lightly, or considered a scuba diving myth. “Raptures of the Deep” is a true physiological problem that has the potential to be fatal for scuba divers.

Source: Bruce Iliff - Suite101.com