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Also known as "the bends" and Caisson Disease, decompression sickness affects divers or other people (such as miners) exposed to rapid changes in air pressure. In recent years, the medical term decompression illness has gained more traction—the term is technically more precise than decompression sickness, but it relates to the same condition.
DCS, as it is commonly known, is caused by a build-up of nitrogen gas in the bloodstream.
When we breathe at sea level, approximately 79 percent of the air we're breathing is nitrogen. As we descend in water, the pressure around our bodies increases at the rate of one unit of atmosphere for every 33 feet of depth, causing nitrogen to be forced from the bloodstream and into adjacent tissues. This process is not actually harmful and it's quite possible for the body to continue to absorb nitrogen until it reaches a point called saturation, which is the point at which the pressure in the tissues equals the surrounding pressure.
The problem arises when the nitrogen in the tissue needs to be released. To remove the nitrogen slowly from the body—a process called off-gassing—a diver must ascend at a slow, controlled rate and carry out decompression stops if necessary; this hovering in the water allows the nitrogen to slowly seep out of the body tissues and return to the bloodstream, where it's released from the body through the lungs.
If a diver ascends too fast, the residual nitrogen in the tissues expands too quickly and forms gas bubbles. These bubbles must normally be on the arterial side of the circulatory system to be harmful—they are usually harmless on the venous side.
Type I decompression sickness is the least serious form of DCS.
It normally involves only pain in the body and is not immediately life threatening. However, the symptoms of Type I decompression sickness may be warning signs of more serious problems.
Joint and Limb Pain Decompression Sickness: This type is characterized by aching in the joints. It is not known exactly what causes the pain as bubbles in the joint would not have this effect. The common theory is that it is caused by the bubbles aggravating bone marrow, tendon and joints. The pain can be in one place or it can move around the joint. It is unusual for bisymmetric symptoms to occur.
Type II decompression sickness is the most serious and can be immediately life-threatening. The main effect is on the nervous system.
Neurological Decompression Sickness: When nitrogen bubbles affect the nervous system they can cause problems throughout the body. This type of DCS normally shows as tingling, numbness, respiratory problems and unconsciousness. Symptoms can spread quickly and if left untreated can lead to paralysis or even death.
Pulmonary Decompression Sickness: This is a rare form of Decompression Sickness that occurs when bubbles form in lung capillaries. Although the majority of the time the bubbles dissolve naturally through the lungs; however, it is possible for them to interrupt blood flow to the lungs, which can lead to serious and life-threatening respiratory and heart problems.
Cerebral Decompression Sickness: It is possible for bubbles that make their way into the arterial blood stream to move to the brain and to cause an arterial gas embolism. This is extremely dangerous and can be identified by symptoms such as blurred vision, headaches, confusion and unconsciousness.
Extreme tiredness is very common in cases of DCS and can sometimes be the only symptom of decompression sickness present.
It is also possible for decompression sickness to occur in the inner ear. This problem is caused by bubbles forming in the cochlea's perilymph during decompression. The result can be hearing loss, dizziness, ringing of the ears and vertigo.
Decompression sickness can manifest itself in many different ways and has many different symptoms, but the most common symptoms are:
Every diver has a different level of risk of Decompression Sickness. Many risk factors are still not fully understood, but there are a few basic factors that doctors agree increase the chance of developing Decompression Sickness:
As there are many risk factors, there are also many methods of prevention. Here's a basic checklist that will help you lower your risk of suffering from Decompression Sickness:
Minor cases of DCS may be treated by medical professionals with oxygen; in time, the excess nitrogen in the body will naturally off-gas. More serious situations, including rapid uncontrolled ascents from significant depth, usually require re-pressurization in a hyperbaric oxygen chamber.
Immediate on the scene treatment consists of oxygen therapy and basic first aid. This should be followed as quickly as possible by recompression treatment in a recompression chamber. When treating decompression sickness, the delay in beginning recompression treatment can be the biggest single cause of residual effects.