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a bubble forms in your tissues, your body reacts to the bubble as if it were a foreign body. Symptoms of DCS can range from a skin rash, extreme fatigue, coughing, and painful joints to paralysis and unconsciousness. You can and must prevent DCS when you dive. During your NAUI Scuba Diver certification course, you will learn to use the NAUI Dive Tables. These tables give you time limits for your diving depths. Staying within the time limits is the first step in preventing DCS. The second step to preventing DCS is to always ascend at a rate no faster than 9 meters (30 feet) per minute when you are using the NAUI Dive Tables to plan your dives. This gives your body a chance to offgas some slight amount of nitrogen as you ascend and to avoid the rapid pressure change that could cause bubble formation. The third step to preventing DCS is to always perform a precautionary decompression stop at 4.5 meters (15 feet) for 3 to 5 minutes. You can also use a dive computer instead of the NAUI Dive Tables to help avoid DCS. Remember that there is always a slight risk that you can suffer DCS even if you follow your NAUI Dive Tables or use your dive computer correctly. If you do suffer DCS, you will need to be treated in a recompression chamber or hyperbaric chamber as soon as possible (figure 4-32). The chamber is pressurized to cause the nitrogen bubbles to go back into solution. Then, the pressure in the chamber is released slowly, so the nitrogen can move from your tissues to your bloodstream, and out with each of your exhalations. Chapter 4- Diving Science If you have any signs or symptoms of DCS, you must seek medical attention immediately. You should never go back under water to try to relieve the symptoms. Nitrogen Narcosis Nitrogen under pressure can also produce an effect on your body called nitrogen narcosis or “rapture of the deep” (figure 4-33). At depths approaching 24 meters (80 feet), nitrogen can be intoxicating. The narcotic effect of nitrogen produces impaired thought and judgment, and it reduces a diver’s physical ability. The danger exists that a diver would be unable to function well enough to ensure their safety. The effects vary by individual and by day. The prevention to this problem is simple: avoid deep dives. The symptoms of nitrogen narcosis increase in intensity with depth. Recovery is as simple as ascending to a shallower depth where nitrogen has no effect. The symptoms leave as rapidly as they occur and there are no after effects. Oxygen Toxicity Oxygen is essential to sustain life, but breathing pure oxygen at depths below about 7.5 meters (25 feet) can be deadly. Oxygen becomes toxic at about that depth and, depending on individual sensitivity, can cause convulsions that can lead to drowning. Scuba Diving Science 117 Nitrogen bubble blockage in capillaries Vein FIGURE 4-31. A PROBLEM CALLED DECOMPRESSION SICKNESS (DCS) CAN OCCUR IF YOU ABSORB A GREAT DEAL OF NITROGEN AND THEN ASCEND TOO QUICKLY. FIGURE 4-32. IF YOU DO SUFFER DCS, YOU WILL NEED TO BE TREATED IN A HYPERBARIC CHAMBER LIKE THIS ONE.


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