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Chapter 5- Decompression and Recompression Decompression and Recompression 169 the elements of combustibles and ignition sources are the only controllable factors. Toxins. In addition to fire hazards, the pressurized gases which chamber occupants breathe can be “toxic.” For example, oxygen at increased pressures can cause seizures. Individuals can usually tolerate 100% oxygen at pressures of 18.3 msw (60 fsw) or less if they are resting. Any physical exertion increases the likelihood of a seizure, as does an increase in body temperature, carbon dioxide buildup, and mental agitation. The dosage of oxygen required is controlled by the total chamber pressure and by the time on oxygen. Seizure-sensitive individuals may not tolerate usual protocols and such instances must be dealt with accordingly. A buildup of carbon dioxide in the chamber from the occupants exhaled gases can cause anything from very minor symptoms to death, depending upon the carbon dioxide levels. To eliminate the carbon dioxide buildup problem, the chamber is “vented” periodically. To vent a chamber, fresh gas is blown into the chamber from the compressor or cylinder bank at the same time as chamber gas is exhausted to the outside. The gas flows must be matched or an overall pressure change within the chamber will occur. Venting is done periodically for short intervals based on a schedule calculated for the chamber and number of occupants. In addition to cleaning the chamber of carbon dioxide, venting also helps to control other occupant waste gases and humidity, thereby assuring overall comfort for those inside. Carbon monoxide and other gas contamination can be a problem in chambers just as in scuba air. This rare problem can be prevented through good compressor maintenance and inspections. Air intakes should be inspected before each run to be sure that chemicals, solvents, paints, and lubricants have not been used or placed near the intake. Compressed cylinder gases purchased from outside sources should be at least smelled and tested for oxygen concentration prior to use. Patient Condition. One of the major concerns in any recompression treatment is the safety and welfare of the subject being treated. Even an individual with a mild case of decompression sickness can become disoriented, fearful, panicky, or combative in the chamber. Chamber personnel are aware of such possibilities and make every effort to inform, forewarn, and comfort individuals under care. Worsening of a patient’s symptoms during treatment is a negative sign and treatment schedules often must be modified to control the situation. Similarly, regression of the symptoms during attempted reductions in chamber pressure may necessitate schedule extensions or a different schedule. As mentioned previously, oxygen can cause seizures. Should a seizure occur, the tender must remove the subject’s oxygen mask and prevent injury. Oxygen seizures are usually brief and require no specific treatment other than removal of the oxygen. The inside tender is very important in severe diving accident cases, and is the most sensitive monitor of subject status and of the means of treating or controlling changing conditions inside the chamber. Chamber Operators & Physicians Need As a patient’s friend or as a diving accident patient yourself, you can do a great deal to help the chamber personnel. The first and most significant step is to plan for safe dives, including accident management plans for evacuation to the nearest recompression facility. Log your dives and know your options for emergency treatment. Second, seek aid when you have reason to suspect someone (including you) has DCS or air embolism. Do not attempt to treat decompression sickness by returning to the water. In-water recompression treatment using air is extremely dangerous and is not recommended. In-water treatment using special equipment, special gas supplies and special expertise has been done. However, it is used only as a last resort even by persons trained and prepared to do so in remote dive operations. As a recreational diver, you must seek chamber treatment. Breathing oxygen on the scene and during transport to a chamber is your first aid of choice. (Please refer to other chapters for diagnosis of decompression sickness and air embolism.) Third, cooperate with chamber personnel by doing what is asked of you and be honest in all answers to questions. Don’t let your ego or your image get in the way of good diagnosis and treatment. If you made one


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