Signs and Symptoms
Due to its perception-altering effects, the onset of narcosis may be hard to recognize. At its most benign, narcosis results in relief of anxiety - a feeling of tranquility and mastery of the environment. These effects are essentially identical to various concentrations of nitrous oxide. They also resemble (though not as closely) the effects of alcohol and the familiar benzodiazepine drugs such as diazepam and alprazolam. Such effects are not harmful unless they cause some immediate danger not to be recognized and addressed. Once stabilized, the effects generally remain the same at a given depth, only worsening if the diver ventures deeper.
The most dangerous aspects of narcosis are the loss of decision-making ability and focus, and impaired judgement, multi-tasking and coordination. Other effects include vertigo, and visual or auditory disturbances. The syndrome may cause exhilaration, giddiness, extreme anxiety, depression, or paranoia, depending on the individual diver and the diver's medical or personal history. When more serious, the diver may feel overconfident, disregarding normal safe diving practices.
The relation of depth to narcosis is sometimes informally known as "Martini's law". This is the idea that narcosis results in the feeling of one martini for every 10 m (33 ft) below 20 m (66 ft) depth. This is a very rough guide, and not a substitute for an individual diver's known susceptibility, or for standard diving safety guides. Professional divers use such a calculation only as a rough guide to give new divers a metaphor, comparing a situation they may be more familiar with.
Reported signs and symptoms are summarized against typical depths in meters and feet of sea water in the following table:
| Pressure (bar) | Depth (m) | Depth (ft) | Comments |
|---|---|---|---|
| 1–2 | 0–10 | 0-33 | Unnoticeable small symptoms, or no symptoms at all. |
| 2–4 | 10–30 | 33–100 | Mild impairment of performance of unpracticed tasks. Mildly impaired reasoning. Mild euphoria possible. |
| 4–6 | 30–50 | 100–165 | Delayed response to visual and auditory stimuli. Reasoning and immediate memory affected more than motor coordination. Calculation errors and wrong choices. Idea fixation. Over-confidence and sense of well-being. Laughter and loquacity (in chambers) which may be overcome by self-control. Anxiety (common in cold murky water). |
| 6–8 | 50–70 | 165–230 | Sleepiness, impaired judgment, confusion. Hallucinations. Severe delay in response to signals, instructions and other stimuli. Occasional dizziness. Uncontrolled laughter, hysteria (in chamber). Terror in some. |
| 8–10 | 70–90 | 230–300 | Poor concentration and mental confusion. Stupefaction with some decrease in dexterity and judgment. Loss of memory, increased excitability. |
| 10+ | 90+ | 300+ | Hallucinations. Increased intensity of vision and hearing. Sense of impending blackout, euphoria, dizziness, manic or depressive states, a sense of levitation, disorganization of the sense of time, changes in facial appearance. Unconsciousness. Death. |
Read more about this topic: Nitrogen Narcosis
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