‘The Bends’: Decompression Sickness Explained

Decompression sickness  — “the bends” — is an illness that can develop if you move from a high pressure to low pressure environment too fast. People who scuba dive, from professional divers to weekend adventurers, can develop decompression sickness. If scuba diving is in your future, here’s everything you need to know about “the bends.”

What causes ‘the bends’?

Decompression sickness can happen when you move from an area of high pressure (underwater) to an area of lower pressure (the surface of the water). At high pressures, gas that’s dissolved in the body is able to move and enter the bloodstream. But as you move back into a lower pressure, the gas moves out of the bloodstream and back into tissue. 

But this move out of the bloodstream should happen over time. If you go to the surface (ascend) too fast, the gas doesn’t have enough time to settle back into place. Instead, it gets trapped in spots it doesn’t belong — like your bloodstream, joints, and the tissue around your bones. Gas can cause damage to the body when it gets trapped like this. 

What are the symptoms of decompression sickness?

Decompression sickness can affect many parts of the body. Symptoms of the bends include:

• Joint pain: Gas bubbles can get stuck in joints and stretch ligaments and tendons in ways they shouldn’t. The result is a deep and throbbing pain that you feel inside your joint. The elbow and shoulder are the most common spots, but you can also get the bends in your knees and hips. 

• Numbness and weakness: If gas bubbles get trapped around the spinal cord, you can develop numbness, tingling, and weakness in your arms or legs. Some people also experience back pain, trouble with bladder control, or even paralysis.

• Trouble talking and walking: Gas bubbles in the bloodstream can interrupt blood flow to the brain. This causes memory loss and trouble speaking or walking (“the staggers”). 

• Skin changes: Gas bubbles can get trapped in smaller blood vessels and in the lymphatic system. This can cause unusual rashes, localized swelling, and skin changes.

• Vertigo: When gas bubbles get trapped in the inner ear, you can develop vertigo. This can cause dizziness, nausea, headache, and ear ringing. 

• Trouble breathing: Some people develop cough, trouble breathing, and chest pain (“the chokes”). These symptoms are not common, unless you’ve gone on a long or very deep dive. 

• Chest pain: Very rarely, gas bubbles enter the arteries and cause an arterial gas embolism. Arterial gas embolisms are life-threatening, and symptoms often look like a heart attack — including chest pain. 

Almost everyone who develops decompression sickness has symptoms within 3 hours of reaching the surface. It’s very rare to develop symptoms more than 24 hours after a dive. 

Who is at risk of getting ‘the bends’?

Anyone who experiences pressure changes can develop decompression sickness. Professional divers and people who work in underwater or tunnel construction are more exposed to pressure changes. So they’re most likely to develop the bends.

But even casual divers can develop symptoms if they ascend to the surface too fast. 

Things that can increase your risk of developing decompression sickness include:

• Long dives

• Deep dives

• Many dives over a few days

• Quicker ascent

If you have a patent foramen ovale (a type of congenital heart problem), you shouldn’t dive without talking to your healthcare provider first. People with patent foramen ovales are at much higher risk for developing severe decompression sickness. 

How do you treat decompression sickness? 

The treatment for decompression sickness is with hyperbaric oxygen therapy. During hyperbaric oxygen therapy, you lie inside a hyperbaric chamber, a tube-like structure. The tube is filled with 100% oxygen and a specialist increases the pressure inside the tube. This treatment helps to dissolve gas bubbles inside the body. 

Studies show that 80% of people with decompression sickness recover completely. People with gas bubbles around their spinal cords and inner ear are more likely to have ongoing symptoms even after treatment. 

How can you avoid getting ‘the bends’?

Whether it’s your first or hundredth dive, always follow protocol for ascent. Following ascent protocol will keep you from rising to the surface too fast and developing decompression sickness. If you’re just learning to scuba dive, always work with certified trainers so you can learn proper ascent techniques. 

The data is clear — it’s dangerous to fly too soon after your last dive. Pressures are lower on an aircraft, which will cause more gas bubbles to form. Experts recommend waiting:

• 12 hours before flying if you’ve been diving for 2 hours or less during the previous 48 hours

• 24 hours before flying if you’ve been doing multiple dives or deeper dives during the previous 48 hours

• 48 hours (or longer) before flying if you’ve been making dives that include decompression stops

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Written by:

Christine Giordano, MD

Christine Giordano, MD, is board-certified in general internal medicine. She received her medical degree from Rutgers New Jersey Medical School and completed residency at Thomas Jefferson University.

Edited by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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