NAUI Master Scuba Diver 118 Diving Physiology DECOMPRESSION SICKNESS (DCS) Decompression sickness (DCS) is a massive topic. Much has been researched, and much is still unknown. Exact mechanisms and contributing factors are not entirely defined. The variety of physical damage done is not completely catalogued. With all that in mind, this section brushes on some of the processes and possibilities. If you stay too long and ascend too quickly, inert gas that you absorb at depth from your breathing mix can come out of solution and form small bubbles in your body. These bubbles are mostly nitrogen. Sometimes you can have bubbles in your body after a dive and not know it. It is not likely to be the case that every dive makes bubbles in your body, however. Theory of decompression and gas transit into and out of your body is covered in Chapter 5. Bubbles can both mechanically and chemically damage your body. Bubbles might squash your blood vessels and nerves from the outside, and obstruct from within. Your body mobilizes defenses against the bubble invaders. White blood cells and platelets clump together and onto bubbles, and your immune system starts reactions called complement activation. A cascade of chemical, blood, nerve, and blood vessel changes takes place, producing a complex assembly of problems constituting decompression sickness. Decompression sickness is also called “the bends,” although “bends” traditionally refers to pain, rather than other manifestations. Even though divers often debate the extent that small factors determine risk, such as how much water you drank that day, your main determinants are how deep you go, how long you stay, and how fast you come up (depth, time, and ascent rate). You can control these with good planning, training, and practice. On a smaller scale, susceptibility to DCS varies with individuals. Predisposing factors are thought to include dehydration, carbon dioxide retention, getting cold, hard work during the dive, post-dive exercise, fatigue, cigarette smoking, alcohol consumption, perhaps increasing age, or impaired circulation to an area of the body. Effects: Effects of decompression sickness start from minutes to hours after ascent and fall along a spectrum from mild to severe. Decompression sickness affects different areas of your body. Effects are not cut and dry, and may overlap. It is not always possible to distinguish the underlying mechanism or the particular effect or effects. This section outlines a few of the possibilities. Limb bends (joint pain) is a common manifestation of DCS. The shoulder and elbow joints are common sites in recreational divers, while lower extremity pain is more likely in commercial divers and tunnel workers. Pain can be vague and mild to piercing and severe. The limb usually looks normal and is usually not tender. Sometimes inflating a blood pressure cuff around the affected limb reduces the pain, depending on the delay and whether the pain is due to joint effects or to nerve irritation from neurological bends. Neurological bends is also a common form of DCS. Effects vary greatly. Seemingly minor problems of weakness, numbness, and “pins and needles” in your arms and legs can mean serious problems with your spinal cord. An often neglected symptom is extreme fatigue, although fatigue is not only a neurological entity. In the most serious cases, urination may become difficult or impossible, and you may lose bowel or sexual function. You may become paralyzed or die. With decompression sickness of the brain, you may have headache, visual changes, paralysis of one side of your body, changes in mental and emotional functioning, difficulty concentrating, or changes in personality. There is some discussion of whether, and to what extent, there are long term brain changes with repeated exposure to decompression stress, even decompression stress that does not result in known decompression sickness. Skin bends may mean simple itchy skin of no consequence after hyperbaric chamber exposure, or a rashy marbling, commonly on your torso that may warn of serious decompression sickness. Inner ear bends is sometimes called “staggers,” because vestibular damage can produce vertigo (a whirling sensation), making you move unsteadily. Other vestibular symptoms are hearing loss, ringing in your ears, and nausea. Chokes is pulmonary decompression sickness, a rare form of DCS that is more common in aviation. Bubbles
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