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CHAPTER 3 — Underwater Physiology and Diving Disorders 3-51 tissue leading to hypoxia, cell injury and death. Arterial gas embolism and autochotonous bubble formation are thought be the primary mechanisms of injury in Cerebral (brain) DCS. The damage done by the direct bubble effect occurs within a relatively short period of time (a few minutes to hours). The primary treatment for these effects is recompression. Recompression will compress the bubble to a smaller diameter, restore blood flow, decrease venous congestion, and improve gas exchange in the lungs and tissues. It also increases the speed at which the bubbles outgas and collapse. 3‑9.3.4 Indirect Bubble Effects. Bubbles may also exert their effects indirectly because a bubble acts like a foreign body. The body reacts as it would if there were a cinder in the eye or a splinter in the hand. The body’s defense mechanisms become alerted and try to eliminate the foreign body. Typical reactions include: n Blood vessels become “leaky” due to damage to the endothelial lining cells and chemical release. Blood plasma leaks out while blood cells remain inside. The blood becomes thick and more difficult to pump. Organ blood flow is reduced. n The platelet system becomes active and the platelets gather at the site of the bubble causing a clot to form. n The injured tissue releases fats that clump together in the bloodstream. These fat clumps act as emboli, causing tissue hypoxia. n Injured tissues release histamine and histamine ­ like substances, causing edema, which leads to allergic ­ type problems of shock and respiratory distress. Indirect bubble effects take place over a longer period of time than the direct bubble effects. Because the non ­ compressible clot replaces a compressible bubble, recompression alone is not enough. To restore blood flow and relieve hypoxia, hyperbaric treatment and other therapies are often required. 3‑9.3.5 Symptoms of Decompression Sickness. Decompression sickness is generally divided into two categories. Type I decom pression sickness involves the skin, lymphatic system, muscles and joints and is not life threatening. Type II decompression sickness (also called serious decom pression sickness) involves the nervous system, respiratory system, or circulatory system. Type II decompression sickness may become life threatening. Because the treatment of Type I and Type II decompression sickness may be different, it is important to distinguish between these two types. Symptoms of Type I and Type II decompression sickness may be present at the same time. When the skin is involved, the symptoms are itching or burning usually accompa­ nied by a rash. Involvement of the lymphatic system produces swelling of regional lymph nodes or an extremity. Involvement of the musculoskeletal system produces pain, which in some cases can be excruciating. Bubble formation in the brain can produce blindness, dizziness, paralysis and even unconsciousness and convulsion.

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