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CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism 17 -9 exhibit certain signs that only trained observers will identify as decompression sickness. Some of the symptoms or signs will be so pronounced that there will be little doubt as to the cause. Others may be subtle and some of the more important signs could be overlooked in a cursory examination. Type I and Type II symptoms may or may not be present at the same time. 17-4.1 Diagnosis of Decompression Sickness. Decompression sickness symptoms us- ually occur shortly following the dive or other pressure exposure. If the controlled decompression during ascent has been shortened or omitted, the diver could be suffering from decompression sickness before reaching the surface. In analyzing several thousand air dives in a database set up by the U.S. Navy for developing decompression models, the time of onset of symptoms after surfacing was as follows: n 42 percent occurred within 1 hour. n 60 percent occurred within 3 hours. n 83 percent occurred within 8 hours. n 98 percent occurred within 24 hours. Appendix 5A contains a set of guidelines for performing a neurological examina - tion and an examination checklist to assist trained personnel in evaluating decompression sickness cases. 17-4.2 Symptoms of Type I Decompression Sickness. Type I decompression sickness includes joint pain (musculoskeletal or pain-only symptoms) and symptoms involving the skin (cutaneous symptoms), or swelling and pain in lymph nodes. 17 - 4.2.1 Musculoskeletal Pain-Only Symptoms. The most common symptom of decompression sickness is joint pain. Other types of pain may occur which do not involve joints. The pain may be mild or excruci ating. The most common sites of joint pain are the shoulder, elbow, wrist, hand, knee, and ankle. The characteristic pain of Type I decompression sickness usually begins gradually, is slight when first noticed and may be difficult to localize. It may be located in a joint or muscle, may increase in intensity, and is usually described as a deep, dull ache. The pain may or may not be increased by movement of the affected joint, and the limb may be held preferentially in certain positions to reduce the intensity (so-called guarding). The hallmark of Type I pain is its dull, aching quality and confinement to particular areas. It is always present at rest and is usually unaffected by movement. Any pain occurring in the abdominal and thoracic areas, including the hips, should be considered as symptoms arising from spinal cord involvement and treated as Type II decompression sickness. The following symptoms may indicate spinal cord involvement: n Pain localized to joints between the ribs and spinal column or joints between the ribs and sternum.

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