As scuba diving grows in popularity, divers need to know their abilities and how to dive within those limits, how to react to emergency situations and how to prevent and treat common medical conditions.
One scuba-diving health problem involves decompression sickness. Decompression sickness, also known as "the bends," is a condition in which nitrogen dissolved in the blood and tissues forms bubbles that block the flow of blood. The bubbles can form when a person moves from a high-pressure environment to a low-pressure environment, which happens when ascending from a dive.
The first symptom is pain. Usually, it occurs in or near an arm or leg joint. At first, the pain may be mild or intermittent, but it may steadily grow stronger and can become severe.
Divers who experience decompression sickness are treated in a pressure chamber. Once in the chamber, the pressure is increased to a level that relieves the victim's symptoms. The pressure is then decreased very slowly until the pressure inside the chamber is equal to outside pressure.
Divers and rescue personnel should know the location of the nearest recompression chamber, the means of reaching it most rapidly and the most appropriate source of consultation by telephone. Use of Divers Alert Network telephone number, 919-684-8111, can be lifesaving.
Failure to provide prompt and appropriate treatment of decompression sickness entails totally unacceptable risk of serious and lasting injury.
Here are some factors related to decompression sickness:
1. Rapid ascents without a three-minute safety stop at 15 feet. As the pressure surrounding the diver lessens during ascent, the nitrogen that has collected in various tissues is released into the blood and is carried to the lungs. A rapid ascent will not allow enough time for the nitrogen to gradually return from the tissues into the blood and then exit with exhaled air. You should ascend no faster than 30 feet per minute. The three-minute safety stop at 15 feet allows nitrogen to leave the body and prevents bubbles from forming in various tissues.
2. Diving beyond the training and experience of the diver. A diver who goes deeper than his or her training level is taking unnecessary risks. Information and courses are available nationwide through the Professional Association of Diving Instructors, National Association of Underwater Instructors, Divers Alert Network and other organizations.
3. Lack of familiarity with and improper use of equipment. This includes buoyancy controls and air-consumption monitors.
4. Diving outside guidelines for no-decompression stop limits. Dive tables and computers provide safety guidelines that take into account the depth of the dive, time spent underwater and time spent on land between dives to help divers avoid decompression sickness.
5. Flying too soon after diving. This is similar to ascending too fast from deep water to the surface. Nitrogen leaves various tissues at various rates of speed. If nitrogen is still in the tissues, the rapid change in cabin pressure may cause it to form nitrogen bubbles that can block blood vessels or disrupt the function of nerves and muscles.
6. Other factors that may contribute to decompression sickness include:
Dehydration. This may result from not drinking enough fluids, sweating excessively or consuming fluids that increase urine output, such as caffeinated drinks or alcohol. Dehydration decreases the amount of blood available for gas exchange and may slow nitrogen removal from the body.
Hypothermia (cold-body temperature). Wearing the appropriate dive suit and shortening the exposure time helps.
Obesity. Fat is known to hold a higher amount of dissolved nitrogen than other tissues. Therefore, the more fat a person has, the more nitrogen the person retains and the slower the nitrogen is removed.
Lack of fitness. Physical fitness decreases body fat and improves a diver's tolerance to exertion. Overexertion can cause fatigue or hyperventilation (breathing too fast). Both situations are uncomfortable and may put a diver in danger.
Alton Thygerson, professor of health sciences at Brigham Young University, is the National Safety Council's first aid and CPR author and technical consultant. For more information, the National Safety Council First Aid Handbook by Thygerson is available in local bookstores.