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Narcosis can produce tunnel vision, making it difficult to read multiple gauges. Nitrogen narcosis is a change in consciousness, neuromuscular function, and behavior brought on by breathing compressed inert gasses, most commonly nitrogen. It has also been called depth intoxication, “narks,” and rapture of the deep.
Narcosis results from breathing gases under elevated pressure, and may be classified by the principal gas involved. The noble gases, except helium and probably neon, [2] as well as nitrogen, oxygen and hydrogen cause a decrement in mental function, but their effect on psychomotor function (processes affecting the coordination of sensory or cognitive processes and motor activity) varies widely.
When inhaled at high partial pressures (more than about 4 bar, encountered at depths below about 30 metres in scuba diving), nitrogen begins to act as an anaesthetic agent, causing nitrogen narcosis. [5] [6] However, the minimum alveolar concentration (MAC) for nitrogen is not achieved until pressures of about 20 to 30 atm (bar) are attained. [7]
Although carbon dioxide (CO 2) is known to be more narcotic than nitrogen – a rise in end-tidal alveolar partial pressure of CO 2 of 10 millimetres of mercury (13 mbar) caused an impairment of both mental and psychomotor functions of approximately 10% – [5] [2] the effects of carbon dioxide retention are not considered in these calculations, as the concentration of CO 2 in the supplied ...
Narcosis while deep diving is prevented by breathing a gas mixture containing helium. Helium is stored in brown cylinders. The most straightforward way to avoid nitrogen narcosis is for a diver to limit the depth of dives. Since narcosis becomes more severe as depth increases, a diver keeping to shallower depths can avoid serious narcosis.
The main reason for adding helium to the breathing mix is to reduce the proportions of nitrogen and oxygen below those of air, to allow the gas mix to be breathed safely on deep dives. [1] A lower proportion of nitrogen is required to reduce nitrogen narcosis and other physiological effects of the
Working the earlier example, for a nitrox mix containing 64% nitrogen (EAN36) being used at 90 feet, the EAD is: EAD = (90 + 33) × (0.64 / 0.79) − 33 EAD = 123 × 0.81 − 33 EAD = 100 − 33 EAD = 67 feet. So at 90 feet on this mix, the diver would calculate their decompression requirements as if on air at 67 feet.
Albert A. Bühlmann recognized the problem [15] [16] [17] and proposed a method which calculated maximum nitrogen loading in the tissues at a particular ambient pressure. [18] [19] Wienke proposed guidelines for decompression diving at altitude in 1993. [20] Egi and Brubakk reviewed various models for preparing tables for diving at altitude ...