Decompression sickness happens when nitrogen that is dissolved in the body under high pressure — for example when diving — forms bubbles when pressure reduces. Key symptoms include joint and muscle pain.

Decompression sickness usually affects deep-sea divers but can also occur in astronauts, compressed air workers, and aviators.

People may also refer to the condition as caisson disease or the bends. Decompression sickness results from the formation of bubbles from dissolved gasses such as nitrogen in the bloodstream and tissues during or after a reduction in environmental pressure.

Decompression sickness is rare and can range in severity. The incidence of decompression sickness depends on:

  • the length and depth of the dive
  • water temperature
  • the intensity of exercise at depth
  • speed of ascent

The incidence can be 3 per 10,000 dives for sports diving and 1.5 to 10 per 10,000 dives for commercial diving. Additionally, the risk for the development of the condition is 2.5 times higher in males than females.

This article discusses the symptoms, causes, treatment, and prevention of decompression sickness. It also answers some common questions about the condition.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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Some common symptoms of decompression sickness include:

Decompression sickness can be one of two types: type I, which is the mild form, and type II, which is the severe form.

Type I decompression sickness most often causes joint pain along with:

Joint pain is the most common outcome of decompression sickness and affects ankles, knees, elbows, and shoulders.

Type II decompression sickness causes severe cardiopulmonary symptoms, such as lung damage, and neurological symptoms such as:

Neurological symptoms appear in 10 to 15% of the cases while cardiopulmonary symptoms are quite rare.

Type II decompression sickness can also cause damage to a person’s spinal cord which may lead to sensory dysfunction, paralysis, or death.

Decompression sickness occurs due to a rapid reduction of pressure following exposure to high pressure. In high-pressure environments, the body absorbs nitrogen or other inert gases to maintain a state of equilibrium.

A sudden reduction in pressure causes the nitrogen to come out of solution and leads to the formation of bubbles.

Accumulation of bubbles near or in joints results in joint pain while their accumulation in the lungs, brain, and spinal cord can cause more serious outcomes.

A few factors that can cause the rapid decrease in pressure are:

  • long or deep dives
  • heavy exercises at depth
  • cold water
  • rapid ascent from depth

Several individual factors may also lead to decompression sickness such as:

However, research into the above factors is not conclusive and further studies are necessary.

The primary treatment option for decompression sickness is the administration of 100% pure oxygen. Scientists recommend this initial treatment until a person with decompression sickness can have hyperbaric oxygen therapy.

There are also other treatments for decompression sickness.


A healthcare professional may administer isotonic glucose-free intravenous fluid to treat decompression sickness since dehydration is common among divers. They may also administer oral rehydration fluids can if the diver is conscious.

Hyperbaric oxygen therapy

Hyperbaric oxygen therapy, or recompression therapy, is a treatment approach where people go into a hyperbaric chamber filled with 100% pure oxygen.

The air pressure in the chamber is higher than the normal air pressure. This helps a person’s lungs collect greater amounts of oxygen.

In-water recompression

This therapy is an alternative to hyperbaric oxygen therapy. It may be suitable for remote locations where a nearby hyperbaric chamber is unavailable or people cannot access quick transport to travel to nearby chambers.

People carrying out in-water recompression take the diver underwater again. This causes the gas bubbles in the diver’s body to return to solution, which reduces symptoms and allows for slow decompression.

However, experts advise that this technique can worsen the condition and generally recommend that people with decompression sickness receive first aid on the surface, not underwater.

If a person is experiencing symptoms of decompression sickness, someone should immediately contact their nearest emergency services by calling 911.

After contacting their nearest emergency services, they can also contact Divers Alert Network (DAN) which provides a 24-hour emergency consultation and assistance. The number to contact DAN is 919-684-9111.

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Some ways to prevent the development of decompression sickness include:

  • avoiding flying within 24 hours of the last dive
  • breathing oxygen at depth
  • developing a conservative dive table that determines a safe time and depth for divers
  • limiting the ascent rate to about 10 meters per minute
  • avoiding back-to-back diving
  • drinking plenty of water before diving

Moreover, people previously diagnosed with decompression sickness should consult with their doctors before returning to diving.

Below are some of the most common questions about decompression sickness.

Can someone survive decompression sickness?

Decompression sickness is different in each case. Some people develop a mild illness while some develop a serious illness.

Early diagnosis and treatment can provide a better chance of full recovery. However, if neglected it may lead to coma and death.

What causes decompression sickness?

Decompression sickness occurs due to a rapid decrease in the pressure surrounding the body after exposure to high pressure.

This, in turn, causes dissolved gases, such as nitrogen, to come out of solution and form bubbles. These bubbles can enter a person’s bloodstream and tissues and cause serious damage to the body.

How long does it take to get the bends?

The development of symptoms of decompression sickness usually takes a few minutes up to 24-48 hours after surfacing. In about 98% of cases, it develops within 24 hours.

Decompression sickness is a condition where bubbles form in a person’s blood and tissues due to a rapid decrease in surrounding pressure. These bubbles can cause joint pain along with severe cardiopulmonary and neurological symptoms.

People experiencing symptoms of decompression sickness should immediately contact emergency services and DAN for appropriate medical assistance.

Divers can also follow a range of safety measures to prevent the development of decompression sickness.