Decompressions Sickness occurs when the body is exposed to a rapid decrease in ambient pressure. It can occur in scuba divers, astronauts during space walks and while flying in unpressurized aircraft.
Nitrogen bubbles form in the blood and tissues after a quick drop in ambient pressure. This can lead to the formation of gas embolisms. The most common manifestation of this condition is joint pain (typically in the elbows and shoulders).
Symptoms
Decompression sickness develops when the body experiences a rapid decrease in pressure, which causes nitrogen bubbles to come out of solution and enter the bloodstream and tissues. This can cause serious and sometimes fatal damage. This condition, commonly known as the bends, can be avoided by properly preparing for dives, limiting depth and duration of dives, and following the recommended recompression procedures.
The first symptom of decompression sickness is often pain, usually in the joints of the arms or legs or back. This may occur immediately or up to 24 hours after exposure to a change in pressure. The pain may be mild or severe, and it may move from one joint to another. It is often described as a feeling of “stiffness” or a feeling that something is “boring into bone.”
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Nitrogen bubbles that enter the bloodstream can produce neurological symptoms, which include blurred vision and headache. They can also lead to numbness or tingling in the hands or feet, unsteadiness when standing up, and dizziness or vertigo. Symptoms related to the respiratory system can include difficulty breathing and chest pain. The condition can also cause a skin rash, and if it is severe it can result in collapsed lung or air embolism.
If symptoms are experienced during a dive, the diver should inform the dive master as soon as possible. If the symptoms do not subside within 48 hours, the diver should visit a doctor and describe the symptoms. It is important that the physician be aware of the person’s recent diving history and experience to help determine if decompression sickness is a likely cause of the symptoms.
A patient suffering from the more severe type of decompression sickness (type II) may have life-threatening symptoms, including pain in the brain and spinal cord and problems with the circulatory or respiratory systems. People who have this form of the disease are more likely to have it after repeated dives in a single day or after flying in an unpressurized aircraft shortly after a dive. This is because nitrogen dissolves readily in fat tissue, and the more fatty areas of the body are more likely to be affected.
Diagnosis
Decompression sickness (DCS) develops when dissolved gases in the body tissues — usually nitrogen — form bubbles as the result of rapid reductions in ambient pressure. The condition typically occurs in deep-sea divers, astronauts and high-altitude aviators who ascend too quickly, but it can also occur in people working in pressurized environments. It can cause potentially fatal problems in the lungs and brain, and is sometimes referred to as the bends or caisson disease.
Nitrogen bubbles may form in the bloodstream or body tissues when the surrounding environment rapidly reduces in pressure, causing nitrogen to come out of solution and create gas bubbles that obstruct blood vessels, trigger inflammation and damage tissue. Symptoms depend on where the bubbles form, but most symptoms involve joint pain — often a dull or sharp ache, but rarely an excruciating burning sensation. This pain typically affects the ankles, knees, elbows and shoulders. The gastrointestinal system and the inner ear can become involved, as well. In rare cases, the lungs can be affected, and this can produce symptoms such as a cough or breathing difficulty.
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Arterial gas embolism has similar symptoms to DCS, but is more serious because the bubbles block blood flow to the heart and brain, resulting in an infarction or stroke. Because of this, it is considered part of the continuum of decompression illness and is treated very similarly.
X-rays and blood tests usually do not show any abnormalities in people with DCS, although skeletal x-rays in long-time divers who have experienced repeated compression-decompression cycles may demonstrate bone damage and chronic joint pain. CT and MRI scans occasionally show edema, infarcts or hemorrhages in the brain and spinal cord in individuals with pulmonary or neurological DCS, but these studies are not reliable diagnostic tools.
The quickest and most effective treatment for decompression sickness is hyperbaric oxygen therapy. This is an emergency treatment in which the patient enters a hyperbaric chamber, where oxygen is delivered under high pressure to drive the nitrogen back into its liquid form and clear it from the body over a period of hours.
Treatment
A sudden reduction in pressure (eg, as one ascends from a dive or exits a caisson) causes gas that was previously dissolved in your blood and tissues to form bubbles. These bubbles can damage blood vessels, blocking normal blood flow and causing pain. The problem can occur in deep-sea divers, astronauts, compressed air workers, and pilots. It is also called the bends, caisson disease, or diving injury.
The symptoms of decompression sickness can range from mild to severe joint and muscle pain to brain or spinal cord problems. They can also cause chest pain, confusion, and personality changes. They can even lead to death.
If you experience a combination of the symptoms, seek medical care immediately. Decompression sickness can be fatal if it is not treated promptly.
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The key to treating decompression sickness is recompression. Recompression therapy can be done in hyperbaric chambers or with the use of nitrox mixtures. Recompression is a gradual return to ambient pressure over several hours, with the goal of eliminating nitrogen bubbles from your body. The process is usually slow because the bubbles have to dissolve slowly in your tissues and blood to escape.
Your doctor can diagnose decompression sickness by asking you about your symptoms and examining you. You may have a blood test or X-rays to rule out other conditions with similar symptoms, such as a herniated disc or an ischemic stroke. You may also have a CT or MRI scan to check for a cerebral or spinal cord injury from decompression sickness. But these tests are not always accurate, and your doctor should start treatment based on clinical suspicion.
Some people develop a late complication of decompression sickness called dysbaric osteonecrosis, or bone death. The symptom is bone pain that gets worse with movement. It happens when the tiny pockets of air (bubbles) that form in your lungs during a deep dive expand and collapse the walls of the pulmonary bullae. This can damage blood vessels in your lungs, resulting in a lung embolism. Bone X-rays may show bone degeneration, but the condition is difficult to distinguish from other diseases of the bones.
Prevention
Decompression sickness, also known as the bends, is a type of barotrauma caused by a rapid decrease in pressure that causes gas bubbles to form inside the body. The gas bubbles can damage tissues, disrupt blood flow and cause pain. The condition can be fatal if left untreated. This condition is preventable by following safe diving practices.
When you dive, your air tank is pressurized with a mixture of oxygen and nitrogen. The oxygen is used by your body while you are underwater, but the nitrogen remains dissolved in your blood and tissue. When you return to the surface, the air pressure drops rapidly, causing the nitrogen to come out of solution and form bubbles in your blood vessels. This causes the symptoms of decompression sickness.
Nitrogen bubbles can form in any part of your body, but they are more likely to form in tissues that have a high fat content, such as your skin and nervous system. This is because the nitrogen can dissolve in fat and other molecules. It is for this reason that scuba divers are especially susceptible to decompression sickness. People who fly in non-pressurized aircraft or use caissons also are at risk of developing decompression sickness, although it is less common for them to experience the symptoms.
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Divers can reduce the risk of decompression sickness by slowly ascending after each dive, taking a safety stop at a certain depth and time interval before continuing to the surface and following a recompression table for the area where they have been diving. A hyperbaric chamber can also help, by exposing the person to a higher air pressure that eliminates nitrogen bubbles from the body.
It is important to see a doctor after experiencing any symptoms of decompression sickness, even if they resolve on their own. If untreated, the condition can lead to permanent damage to the lungs, bones or brain and may be fatal. If you have experienced the symptoms of decompression sickness, avoid scuba diving until your doctor clears you to do so. If you have been cleared by a doctor to resume diving, follow the guidelines set out by your instructor.
