Decompression Sickness


What Is It?

Decompression sickness, also called generalized barotrauma or the bends, refers to injuries brought about by a rapid decrease in the pressure that surrounds you, the pressure of either air or water. It occurs most commonly in scuba or deep-sea divers, although it also can occur during high-altitude or unpressurized air travel. However, decompression sickness is rare in pressurized aircraft, such as those used for commercial flights.

When you scuba dive with compressed air, you take in extra quantities of oxygen and nitrogen. The oxygen is used by your body, but the nitrogen is dissolved into your blood, where it remains during your dive. As you swim toward the surface from a deep dive, the water pressure around you decreases. If this transition occurs too quickly, the nitrogen does not have time to clear from your blood. Instead, it separates out of your blood and forms bubbles in your tissues or blood. The nitrogen bubbles cause decompression sickness. The condition commonly is called the bends because joint pain is a common symptom.

What happens inside your body during decompression sickness is just like what happens when you open a carbonated beverage. When you open the beverage, you decrease the pressure surrounding the beverage in the container, which causes the gas to come out of the liquid in the form of bubbles. If nitrogen bubbles form in your blood, they can damage blood vessels and block normal blood flow.

Factors that put you at higher risk of decompression sickness include:

  • Being older than 30
  • Being female
  • Low cardiovascular fitness
  • High body-fat percentage
  • Use of alcohol or tobacco
  • Fatigue, seasickness or lack of sleep
  • Injuries (old or current)
  • Diving in cold water

If you have severe asthma or another lung disease, you should discuss diving safety with a physician. People with longstanding asthma may have developed thin-walled air pockets in the lungs called bullae that do not empty quickly when a breath is exhaled. As you are returning to the surface after a deep dive, air in the bullae may expand. If a bulla ruptures, it can cause a collapsed lung or allow a relatively large air bubble (called an air embolism) to reach your central circulation system. An air embolism can result in a stroke. Although there are few examples of this complication, caution is advisable.


Symptoms of decompression sickness include:

  • Joint pain
  • Dizziness
  • Extreme fatigue
  • Tingling or numbness
  • Weakness in arms or legs
  • A skin rash
  • Unconsciousness or paralysis, in severe cases


Your diving history and symptoms are key factors in diagnosing decompression sickness. Blood tests and X-rays usually do not show any signs of the problem, although they may be performed if the diagnosis is not clear.

Expected Duration

Joint pain from decompression sickness can persist for days or weeks.


To minimize the risk of decompression sickness while diving:

  • Descend and ascend slowly in the water, and don’t stay at your deepest depth longer than recommended. Scuba divers typically use dive tables that tell you how long you can remain at a given depth.
  • Do not fly within 24 hours after diving.
  • Avoid consuming alcohol before diving.
  • Avoid hot tubs, saunas or hot baths after diving.
  • Make sure you are well hydrated, well rested and prepared before you scuba dive. If you recently have had a serious illness, injury or surgery, talk to your doctor before diving.


Emergency treatment for decompression sickness initially involves maintaining blood pressure and administering oxygen. Fluids also may be given. The key to treatment is the use of a hyperbaric oxygen chamber, a high-pressure chamber in which the patient is given 100 percent oxygen. Treatment in a hyperbaric chamber reverses the pressure changes that allowed gas bubbles to form and drives nitrogen back into its liquid form, so that it can be cleared more gradually over a period of hours. It is not recommended that divers with decompression sickness attempt to treat themselves with deep diving. People with lung-related symptoms, skin rashes or neurological symptoms of decompression sickness also should be treated with hyperbaric oxygen.

When To Call A Professional

If you experience symptoms of decompression sickness after scuba diving or flying, get to a doctor as soon as you can. Hyperbaric treatment has its greatest success if given within several hours after symptoms start.


Most cases of decompression sickness respond well to a single treatment with hyperbaric oxygen. Your doctor may suggest repeated treatments if you are still experiencing symptoms. In rare cases, divers with neurological symptoms may require up to 20 treatments.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.