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Chapter 5- Decompression and Recompression Decompression and Recompression NAUI recognizes enriched air nitrox (EANx) diving 163 and has a comprehensive program available to properly train divers in its use (table 5-3). Divers should seek specific training before using any mixtures other than air. More details on mixed gas diving may be found in the “Technical Diving” chapter of this book. Aids to Decompression A variety of equipment and information sources are available to help you make decisions about decompression. None of these, however, can make decisions for you. You decide how deep to dive and how long to remain at depth. These two considerations are the most important in avoiding decompression sickness. Although the devices mentioned here such as dive computers can give good advice, it is your decision to avoid pushing the limits that will help you prevent decompression sickness. The most common aid to decompression, the dive tables, has been discussed. Modified U.S. Navy tables are available in a variety of formats on plastic cards to carry with you on your dive. Aside from tables, additional equipment available for use in for decompression calculations includes capillary depth gauges, diaphragm depth gauges, oil-filled depth gauges, analog watches, digital watches, analog bottom timers, digital bottom timers, and dive computers (some of which can be programmed by the user), all of which can be purchased in your local dive shop. These items are discussed in the equipment chapter. HYPERBARIC CHAMBERS The treatment for serious diving problems such as decompression sickness or air embolism is recompression, which is carried out in a hyperbaric chamber. Hyperbaric Chambers and the Recreational Diver Chambers are often not covered in much detail in entry level scuba courses and divers usually have no first-hand contact with them until treatment is needed. Familiarity with chambers may alleviate any fears associated with them and better prepare you as a diver to deal with incidents which might befall you or people you know. One type of diver treated consists of those with an “unexpected” hit. This is the statistically significant group of individuals who do everything “by the book” and still suffer decompression sickness or air embolism. There will always be a small unpredictable incidence due to individual variations and undetectable abnormalities. This is the risk that all divers assume when they dive. The “over-the-limits” diver falls into a second group of “expected” hits. These are divers who have taken their diving activities beyond the limits of their tables or computer. Other examples include the diver who takes up deep repetitive diving without adequate guidance and the egotistical diver who, because of anecdotal experience, thinks that the “odds can be beaten” and liberalizes or experiments with diving activities. Divers using dive computers without knowing their limitations are also subject to decompression problems. Another type of diver treated can be classified as “inadequately trained.” In this group are the totally untrained divers who use scuba with no instruction. Unfortunately, these divers usually require treatment for air embolism secondary to breath holding upon ascent. Another example is the novice diver who knows enough to go diving, but not enough to monitor depth/time parameters and avoid decompression sickness. Whether this lack of knowledge is due to total ignorance or the inadequate development of good habits is irrelevant. Training must establish a general understanding of decompression, an internalization of the importance of following decompression guidelines, and the ingraining of good habits that will optimize safety. The following sections present an overview of chambers. They will familiarize you with some common vocabulary and provide you a basis for further exploration of the devices available for treating diver injuries. COMPARISON OF DEPTH LIMITS FOR MAX. PO2 GAS %N2 %O2 MAX DEPTH Air 79 21 67m 220' Nitrox I 68 32 40m 130' Nitrox 2 64 36 33m 110' TABLE 5-3. STANDARD NITROX MIXES


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