Nitrogen narcosis is not harmful to your body but it can have a strong influence on your diving performance. Narcosis affects everyone on deep dives and everyone is affected differently, especially psychologically. As a general rule it works on your psyche like alcohol does. In terms of diving it can lead to poor decision making or an inability for the diver to recognize or respond to a developing problem before it leads to a worse one. Divers generally agree that you can learn to recognize, anticipate and adapt to the effects of nitrogen narcosis so that your performance isn't as badly impaired. However, this adaptation takes time and exposure to the specific effects of nitrogen narcosis on you. If you or your buddy are being strongly affected by nitrogen narcosis then ascending slightly, 10 feet or more, will significantly reduce the symptoms.
Symptoms of narcosis will generally appear at a given depth, which will vary from diver to diver, and also will vary within the same diver from dive to dive. Generally the symptoms won't get any worse with prolonged exposure if the diver remains at the same depth but will progressively worsen if the diver continues to a deeper depth, or will progressively improve if the diver ascends to a shallower depth.
The chemical processes that cause nitrogen narcosis are not well understood. Nitrogen is considered an inert gas, and doesn't create any chemical reactions in our body. However, some diving scientists believe that the dissolved nitrogen in our body tissues somehow blocks impulses traveling between certain nerves in the brain. What we do know is that nitrogen narcosis reduces our ability to concentrate, and to perceive and respond to problems we might encounter. It should also be noted that oxygen is as narcotic as nitrogen, and that divers who breathe nitrox will have the same tendency toward narcosis as those on air.
The signs and symptoms of nitrogen narcosis have been compared to those experienced by alcohol or general anesthesia. The earliest symptoms affect brain functions such as concentration, memory and judgment. How those effects manifest themselves in the diver will depend on the individual. For example, a diver who is very confident in his or her ability might start feeling a sense of euphoria. But a diver who is not secure with their skills or surroundings may experience a sense of anxiety. In both cases, these symptoms may indirectly cause trouble the former may lead to poor decision-making, while the latter may lead to stress.
As we continue deeper, narcosis starts to affect motor functions. Movement becomes more difficult and coordination is reduced. A diver may experience difficulty reading or interpreting the display on a dive computer or making adjustments for buoyancy control. Furthermore, the diver may develop tunnel vision or have trouble remembering things such as the agreed-upon maximum depth, no-decompression limits, or turnaround pressure. The diver may react slowly to directions or visual cues from a buddy, or make serious errors in judgment that can lead to an accident.
As the diver continues deeper still, symptoms can become even more serious such as hallucinations or even unconsciousness.
When you first begin to experience symptoms of narcosis or recognize signs of it in your dive buddy a prudent thing to do would be to stop your descent and assess your ability to continue. If you feel any anxiety or loss of control or notice the same in your dive buddy ascending to a shallower depth is advisable.
Some divers are more susceptible to narcosis than others. Some divers will not recognize the symptoms in themselves, or will recognize them in their dive buddyÃÔ behavior before the dive buddy realizes that they are narced. Our physical and mental state can have a significant impact not only on our susceptibility to narcosis, but also on how the symptoms manifest themselves. Symptoms can vary within the same diver from dive to dive. Certain factors, however, appear to increase the effects of narcosis. These factors include:
- Inexperience, or a lack of confidence in oneÃÔ abilities
- Fatigue or exertion
- Cold water
- Rapid descent
- Poor visibility
- Carbon dioxide buildup (hypercapnia)
- Task loading
The good news is that narcosis can be managed by the diver. Ascending to a shallower depth will reduce the symptoms progressively as you ascend or will make them go away altogether. However, since narcosis is predominantly a mental disorder, even such things as focusing on your gauges or concentrating on a task will help make the symptoms more manageable. But keep in mind that if you are narced, the chances are very good that your dive buddy will be too. So a prudent thing to do would be to signal to your buddy to ascend a little bit to reduce the effects.
There is some evidence that prolonged exposure to narcosis helps a diver to mentally adapt to its effects. Many deep air divers use the technique of making progressively deeper dives to train themselves to perform under the effects of narcosis. This technique, however, is increasingly going out of favor as divers are learning better alternatives. One of those alternatives is the use of helium mixtures to reduce the level of nitrogen in our breathing mix (and therefore the effects of narcosis). Several scuba training agencies offer classes in the use of trimix for deeper recreational diving.