Nitrogen Narcosis or “raptures of the deep” is an altered mental state caused by the increased pressure of gas in your body. Most divers will start getting affected by this sensation around 30 meters, and the effects will increase by depth.
Most commonly we dive on normal compressed air, comprised by mostly oxygen and nitrogen. Due to the large amount of nitrogen, this gas has the largest impact on narcosis as we descend. The concentration of nitrogen impairs the conduction between our nerve impulses, which resembles the influence of alcohol. As we go deeper the pressure increases, with that the narcosis starts affecting our mental abilities.
Just like drinking small amounts of alcohol, the narcosis itself is not harmful. However, being under the influence 30 meters under the surface can lead to accidents, the same as driving a car intoxicated could. Unlike other drugs the narcosis subsides quite rapidly as the diver ascends, and pressure decreases.
The symptoms of narcosis is the same as anesthetic drugs, causing the diver to feel symptoms like dizziness, euphoria, slowing of reaction time, loss of dexterity, perceptual narrowing, numbness and amnesia.
As the diver continues to dive at this depth he will go through series of different mental states. This includes going from a relaxed, euphoric and overconfident level to a sensation of panic thoughts and terror. This means that a diver, who has experience of making short deep dives, will experience something completely different when staying down there for a period of time.
There is also a general belief that predisposing factors like cold, darkness, clear blue water, sea sickness and hard work underwater has great effect on the severity of the narcosis. A diver, who shows no signs or symptoms on a deep dive one day, can experience narcosis on another.
Divers sometimes believe they are not affected by narcosis after a dive, but this can simply be because the symptoms where disguised by task loading or other factors. Just as a person can think he is not affected by having a couple of drinks. Diving deeper than 30-40 meters will produce some kind of narcosis, the symptoms might not just be as visible.
There are two ways of preventing narcosis. By keeping above 30 meters, you should stay relatively symptom free. The other way is to mix helium, a less narcotic gas, in your cylinder. This will make deep dives more manageable, however mixed gas diving requires some additional training and equipment.
But by managing narcosis, keeping up to date with your training and staying physically fit, you can experience some of the most mystical places on earth.
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