What Is Decompression Sickness?

Decompression sickness happens when dissolved gases in the body form bubbles after a rapid decrease in pressure. It is most commonly associated with scuba diving, but it can also affect aviators, astronauts, and tunnel workers. The condition ranges from mild joint pain to life-threatening neurological damage, and it requires prompt medical evaluation.

What Is Decompression Sickness?

Decompression sickness, sometimes called “the bends,” occurs when nitrogen bubbles form in tissues and blood. When you breathe compressed air underwater, your body absorbs extra nitrogen. As you ascend, pressure drops. If the ascent is too fast, nitrogen cannot be eliminated quickly enough through the lungs. It comes out of solution and forms bubbles.

These bubbles can block blood vessels, stretch tissues, and trigger inflammation. The effects depend on where the bubbles travel and how many form. A diver with mild symptoms may feel tired or have a rash. A severe case can cause paralysis or death. Early treatment with oxygen and recompression therapy is the standard of care.

What Causes Decompression Sickness?

The underlying cause is always the same: a pressure drop that is too rapid for the body to handle safely. In diving, this happens during ascent. The longer and deeper the dive, the more nitrogen the body absorbs. Staying at depth for extended periods increases risk. So does making multiple dives in a single day.

Other factors raise the risk even when dive profiles are conservative. Cold water, dehydration, fatigue, and obesity all increase susceptibility. Flying too soon after diving is another common trigger. The reduced cabin pressure in an airplane can cause bubble formation hours after a dive has ended. Most diving organizations recommend waiting at least 12 to 24 hours before flying.

What Are the Symptoms of Decompression Sickness?

Symptoms usually appear within a few hours of surfacing. In some cases, they start while the diver is still underwater or during the ascent. About half of all cases show symptoms within one hour. Nearly all cases appear within six hours.

Mild symptoms include joint pain, usually in the shoulders, elbows, or knees. Fatigue, dizziness, and a blotchy skin rash can also occur. These are sometimes called Type I decompression sickness.

Severe symptoms involve the nervous system or lungs. Numbness, tingling, weakness, confusion, and difficulty walking are signs of spinal cord involvement. Chest pain, coughing, and shortness of breath suggest pulmonary decompression sickness, sometimes called “the chokes.” Vision changes, hearing loss, and loss of bladder control are also serious warning signs. Any neurological symptom after diving requires emergency evaluation.

How Is Decompression Sickness Diagnosed?

Diagnosis is primarily clinical. A doctor evaluates the patient’s dive history and symptoms. There is no single blood test or scan that confirms decompression sickness in every case. Imaging can help rule out other conditions, but a negative scan does not exclude the diagnosis.

Doctors use established criteria to classify the severity. The key question is whether symptoms are mild or serious. Mild symptoms may resolve without treatment, but they can also progress. Serious symptoms always require immediate recompression therapy. When in doubt, medical professionals treat for decompression sickness rather than wait.

How Is Decompression Sickness Treated?

First aid begins with 100 percent oxygen. Breathing pure oxygen helps flush nitrogen from the body faster. It also reduces bubble size. Anyone suspected of having decompression sickness should receive oxygen immediately, even if symptoms seem mild.

Definitive treatment is recompression therapy in a hyperbaric chamber. The patient is placed in a pressurized chamber and breathes oxygen at increased pressure. This forces bubbles to shrink and dissolve. The pressure is then reduced gradually in stages, allowing the body to eliminate nitrogen safely.

Treatment should begin as soon as possible. Delays can make recovery less complete. Most patients improve significantly after one or more sessions. Some need multiple treatments over several days. Complete recovery is common, but severe cases can leave permanent damage.

How Can Decompression Sickness Be Prevented?

Prevention is straightforward in theory but requires discipline in practice. Follow dive tables or dive computer limits. Ascend slowly and make safety stops. Never dive beyond your training or experience level.

Stay well hydrated before and after dives. Avoid alcohol, which dehydrates and impairs judgment. Do not exercise heavily immediately after diving. Cold water increases risk, so use adequate thermal protection. Plan surface intervals between dives and wait the recommended time before flying.

Dive computers are useful tools, but they are not infallible. They estimate, not measure, nitrogen load. Individual physiology varies. A dive that is safe for one person may cause problems in another. Conservative diving is always the safer choice.

When Should You Seek Emergency Care?

Any symptom that appears after diving deserves attention. Joint pain that starts within hours of surfacing should not be dismissed as a muscle strain. Numbness, weakness, confusion, or difficulty breathing are emergencies. Call emergency services or go to the nearest emergency department immediately.

Tell the medical team that you have been diving. Give them details about your dive profile if you can. This information helps them decide on treatment. Do not wait to see if symptoms improve on their own. Early treatment significantly improves outcomes.

Can Decompression Sickness Happen Without Diving?

Yes, though it is less common. High-altitude aviators and astronauts can develop decompression sickness when cabin pressure drops. This is why military pilots breathe oxygen before high-altitude flights. Tunnel workers and caisson workers face similar risks when moving between pressurized and normal environments.

Altitude decompression sickness is generally milder than diving-related cases. Symptoms are similar: joint pain, fatigue, and neurological signs. The treatment is the same. Anyone with symptoms after rapid altitude exposure should seek medical evaluation.

What Is the Long-Term Outlook After Decompression Sickness?

Most people recover fully with prompt treatment. Studies show that the majority of divers treated for decompression sickness have complete resolution of symptoms. Recovery can take days to weeks. Some individuals experience lingering fatigue or joint discomfort.

Severe cases carry a higher risk of permanent damage. Spinal cord involvement is the most concerning. Permanent weakness, numbness, or bladder dysfunction can occur. The risk of lasting damage increases when treatment is delayed.

Having decompression sickness once does not mean you cannot dive again. However, it is worth discussing with a diving medicine specialist. Some people have anatomical features, such as a patent foramen ovale, that increase risk. This is a small hole between the heart’s upper chambers that can let bubbles bypass the lungs and reach the brain. Testing for this condition is not routine, but it may be considered after recurrent episodes.