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A diver returning to the surface from a deep dive must undergo decompression during which inert gas is eliminated from his body. This requires the diver to stop at specified depth increment for specified periods of time before continuing his ascent. The U.S. Navy Standard Air Decompression Table defines the required increments of depth and time to properly decompress from an air dive. Circumstances can occur, however, in which decompression procedures cannot be followed in the water. In these cases, the decompression must be carried out in a recompression chamber.

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Surface Decompression. There are sions, particularly after deep dives or relatively shallow dives of long exposure time, where sea conditions such as strong currents, cold water, heavy weather, or other emergencies prevent a diver from taking adequate decompression time in the water while ascending to the surface. Surface decompression in a recompression chamber is then required (See Sections 10, 11, and Appendix D). Decompression Accidents. Decompression accidents, such as decompression sickness or gas (air) embolism, require treatment in a recompression chamber.

It is important to note that the use of a recompression chamber is the only technique presently known that can adequately deal with the two circumstances outlined above. Recompression in the water is not generally possible nor practical in either case.

16.1 RECOMPRESSION CHAMBERS

A recompression chamber is a pressure vessel capable of simulating depth. Two configurations of recompression chambers are most common: the single lock chamber and the double lock chamber. Single lock chambers, as the name implies, contain only

one pressure compartment. Double lock chambers contain two chambers capable of being pressurized independently. The double lock chamber possesses significant advantage over the single lock in that medical personnel and tenders may enter and exit the chamber to render aid during treatment of a stricken diver. Both the single and double lock chambers should be equipped with the following systems:

1. A two-way communications system.
2. Demand oxygen breathing apparatus.
3. Pressurization and exhaust systems.
4. Fire extinguishing system.
5. External lighting.

6. View ports.

7. Depth control gauges, control manifolds. 8. A medical lock to allow entry of food or medicine.

9. Heating and air conditioning systems (highly desirable).

10. Stop watches (elapsed time with hour, minute, and second hands).

Recompression chambers are usually cylindrical steel pressure vessels designed to withstand an internal working pressure of at least 5 to 6 atmospheres (75 to 90 psig).

The U.S. Navy has two basic chamber configurations: a double lock chamber capable of withstanding an internal pressure of 200 psi (Figure 16-1); and a single lock chamber capable of withstanding 100 psi (Figure 16-2). Most recompression chambers are 54-60 inches in inside diameter, but may vary from as little as 30 inches to as large as 10 feet inside diameter. Large chambers used to decompress divers after long periods of saturation are comfortably outfitted with toilet facilities, cots, and showers, but these are generally found only at sites where large scale diving operations are being conducted.

Small, portable chambers that allow the immediate recompression of a diver are valuable, especially

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16.1.2 Recompression Chamber Operator Qualifications and Training (U.S. Navy Recompression Chamber Operator's Handbook 1973)

The operator of a recompression chamber must be thoroughly trained in the mechanical operation of the chamber, and able to recognize the symptoms of decompression sickness and gas embolism.

A chamber operator must:

■ Calculate the amount of gas required to take the chamber to depth; ventilate it and determine amount of backup gas required.

Operate all mechanical systems including air compressors, and maintain and control the air supply to the chamber.

Recognize and eliminate all sources of combustible materials in the chamber.

Ensure the existence of adequate fire-fighting materials in the chamber.

■ Check all fittings and arrange for oxygen supply. ■ Determine ventilation requirements for oxygen

breathing if no O2 dump system is installed. Ensure the accuracy of all gauges and timing devices.

Thoroughly understand U.S. Navy treatment tables and know how to use them. Understand first aid.

16.1.2.1 Manning Requirements

In conducting a recompression treatment, all attending personnel must work as a team for the benefit of the patient. Tenders often initially control recompression from inside the chamber and tend the patient with the advice of a physician familiar with divers' diseases. Outside tenders normally operate the chamber, monitor the time and depth, and communicate with inside personnel.

The minimum team recommended for any recompression treatment consists of:

■ Dive Master-In complete charge of the operation. Outside tender #1- Responsible for operation of the gas supplies, ventilation, and pressuriza

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