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CHAPTER 3 — Underwater Physiology and Diving Disorders 3-41 3‑9.1.1 Causes of Nitrogen Narcosis. Breathing nitrogen at high partial pressures has a narcotic effect on the central nervous system that causes euphoria and impairs the diver’s ability to think clearly. The narcotic effect begins at a nitrogen partial pressure of approximately 4 ata and increases in severity as the partial pressure is increased beyond that point. A nitrogen partial pressure of 8 ata causes very marked impairment; partial pres sures in excess of 10 ata may lead to hallucinations and unconsciousness. For a dive on air, narcosis usually appears at a depth of approximately 130 fsw, is very prominent at a depth of 200 fsw, and becomes disabling at deeper depths. There is a wide range of individual susceptibility to narcosis. There is also some evidence that adaptation occurs on repeated exposures. Some divers, particularly those experienced in deep operations with air, can often work as deep as 200 fsw without serious difficulty. Others cannot. 3‑9.1.2 Symptoms of Nitrogen Narcosis. The symptoms of nitrogen narcosis include: n Loss of judgment or skill n A false feeling of well ­ being n Lack of concern for job or safety n Apparent stupidity n Inappropriate laughter n Tingling and vague numbness of the lips, gums, and legs Disregard for personal safety is the greatest hazard of nitrogen narcosis. Divers may display abnormal behavior such as removing the regulator mouthpiece or swimming to unsafe depths without regard to decompression sickness or air supply. 3‑9.1.3 Treatment of Nitrogen Narcosis. The treatment for nitrogen narcosis is to bring the diver to a shallower depth where the effects are not felt. The narcotic effects will rapidly dissipate during the ascent. There is no hangover associated with nitrogen narcosis. 3‑9.1.4 Prevention of Nitrogen Narcosis. Experienced and stable divers may be reasonably productive and safe at depths where others fail. They are familiar with the extent to which nitrogen narcosis impairs performance. They know that a strong conscious effort to continue the dive requires unusual care, time, and effort to make even the simplest observations and decisions. Any relaxation of conscious effort can lead to failure or a fatal blunder. Experience, frequent exposure to deep diving, and training may enable divers to perform air dives as deep as 180 ­ 200 fsw, but novices and susceptible individuals should remain at shallower depths or dive with helium ­ oxygen mixtures.

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