Treating Decompression Illness

By Fred Bove, M.D., Ph.D

It is not common to develop a decompression related illness, but if you do, you should know something about the different forms of treatment for decompression sickness (DCS) or arterial gas embolism (AGE). These two injuries together are often referred to as decompression illness (DCI). There are many manifestations of DCI. These can include pain in an elbow or knee, or a neurologic injury that produces numbness or weakness in a leg, difficulty with urination, or paralysis. Even more severe injury can occur from pulmonary barotrauma and arterial air embolism. Regardless of the seriousness of your symptom, your next step is to recognize the fact that you have decompression sickness or air embolism, and need recompression therapy. You may seek treatment yourself in a hyperbaric chamber after the dive, or might be transported to a hyperbaric chamber.

When you learn about therapy, you will discover that the most common treatment tables were developed by the United States Navy and have been in use for many years in the treatment of decompression illness. There are also treatment tables from the British Navy, from France, and an interesting one from Australia that involves returning to depth in the water. This was developed because dive sites in the South Pacific can be far from a treatment facility.

Most treatment tables will take you to a depth of 60 feet for usual types of decompression sickness, to 100 feet when injuries are severe, and to 165 feet if the physician feels that brain injury from AGE is most likely to improve with greater bubble compression.

Treatment for DCS and AGE usually starts with a recompression to 60 feet on 100 percent oxygen. This begins the standard Navy Table 6. In some cases, when only a joint is involved, a short 60 feet oxygen table (U.S. Navy Table 5) may be used. Both tables expose the injured diver to 60 feet of 100 percent oxygen for a period of time, then ascend to 30 feet and provide further exposure to 100 percent oxygen. U.S. Navy Table 6 (see chart) provides short intervals of air breathing to avoid oxygen toxicity.

In the past, treatment of arterial air embolism with evidence of brain injury involved use of Table 6a. It begins with a recompression to 165 feet on air, or a mixture of 50 percent oxygen in nitrogen. After 20 minutes at 165 feet, the diver is brought to 60 feet and the remainder of the treatment is similar to Table 6. Research has demonstrated that Table 6 usually provides the same benefit as Table 6a, which is now used for refractory DCI that is not improving with Table 6. Most treatment protocols described the use of Navy Table 4 when treatment fails with either Table 6 or Table 6a. Table 4 is one of several saturation tables. These expose divers to treatments in excess of 24 hours and are usually reserved for large hyperbaric facilities. Navy Table 7 can be used for severe cases of DCI that have not responded to more conventional therapy.

In-water Recompression Therapy
Divers in the South Pacific developed treatment tables that involve underwater treatment. This is because of long distances and prolonged delays expected when a diving accident occurs in remote sites. These treatments follow a planned schedule, and use oxygen in a fashion similar to other tables—supplied through a full-face mask. Appropriate diving dress is needed to keep the injured diver warm. Equipment also includes some form of communication between the surface, the attendant and the injured diver. Treatment begins when the diver is lowered to 30 feet, breathing 100 percent oxygen. After 30 minutes in mild cases or 60 minutes in severe cases, the diver begins ascent at a rate of four minutes per foot. Total elapsed time for a mild case would be about two and one-half hours, and for severe cases about three hours. Upon surfacing, the injured diver is given surface oxygen, alternating one hour on oxygen and one hour on air for 12 hours. For comparison, U.S. Navy Table 6 has a minimum time of four hours and 45 minutes, but can be extended by adding additional oxygen periods at either 60 feet or 30 feet. U.S. Navy Table 4 requires 38 hours and 11 minutes. U.S. Navy Table 7 begins at 60 feet on oxygen; minimum time at 60 feet is 12 hours and the patient uses periodic oxygen breathing as in Table 6. Decompression starts with two-foot excursions. The total ascent time from 60 feet to the surface is about 36 hours.

Chamber Configurations
The treatment tables must be modified when single-person chambers, or monoplace chambers, are used. These are usually compressed with 100 percent oxygen and the patient breathes the chamber gas. In a large chamber facility (a multiplace chamber), the chamber is compressed with air and several patients breathe oxygen through masks. Air breaks are possible by removing the masks. Monoplace therapy is usually provided at 30 feet to avoid oxygen toxicity. Treatment should account for the severity of the illness and the need for medical support. Unconscious divers requiring assisted respiration can be treated in a monoplace chamber, but they are better cared for in a multiplace chamber.

It is always important to locate the nearest treatment facility when planning a dive trip, and be sure that the dive operation manager or boat captain has a protocol for medical evacuation of an injured diver. This information should be shared with the diving group.

Information about the nearest facility can be obtained by calling the Divers Alert Network. Divers are also advised to purchase insurance to provide funding for transportation and treatment of a diving injury.