by Badash M
(Caisson Disease; Altitude Sickness; Dysbarism; The Bends; DCS)


Decompression sickness (DCS) occurs when the body is exposed to a sudden drop in surrounding pressure. It happens most often during a deep sea dive or when flying in a non-pressurized plane.


DCS is caused by gas bubbles in the blood and tissues. At normal altitudes, nitrogen and other gases leave through the lungs or are dissolved in the blood and tissues. Severe changes in altitude and air pressure allow nitrogen and other gases to escape from blood or tissue and form gas bubbles. These bubbles block the flow of blood. This condition can be fatal if not treated quickly.

Risk Factors

The only risk factor for DCS is a reduction in pressure. This can happen with:

  • Rising too quickly to the surface from deep sea scuba diving
  • A fast ascent into a high altitude from a low altitude
  • Sudden exit from a high pressure or hyperbaric chamber
  • Increased depth of dive
  • Long duration of dive
  • Multiple dives in one day
  • Flying after diving
  • Diving in cold water
  • Fatigue
  • Exertion
  • Dehydration
  • Obesity
  • Advanced age


The less severe type of DCS is called DCS I. It causes inflammation of muscles, joints, and tendons, It causes pain and swelling, which is more common in arm or leg joints. The pain may become more severe over time. Itching, skin mottling, weakness, and fatigue also occur.

The more severe type of DCS is called DCS II. This results in more serious bodywide problems. In the most severe form, it may lead to paralysis and even death. Other symptoms of DCS II include:

  • Numbness and tingling
  • Stomach pain
  • Back pain
  • Headache
  • Dizziness
  • Confusion
  • Vision problems
  • Vertigo —the sensation of movement when standing still
  • Chest pain and severe coughing (less common)
  • Shock

A mild form of DCS I can become chronic in frequent divers. It may go undetected. Over time, this mild form can lead to breakdown of joints and bones.

Progressive Joint Damage
Damaged Joint
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The doctor will ask about symptoms and past health. A physical exam will be done. DCS will be suspected based on symptoms and recent diving or pressure exposure. Treatment is often started right away. Blood and other diagnostic tests are not usually helpful.


DCS needs to get treated right away. In severe cases, delaying treatment may be fatal. Treatment should be given even if initial symptoms are mild or disappear. Proper treatment, given quickly, should cure all symptoms of DCS.

Breathing 100% oxygen from a mask may be appropriate for DCS I. Treatment also includes careful monitoring for other symptoms.

Treatment for DCS II is oxygen therapy in a hyperbaric chamber. The chamber gradually increases and then decreases air pressure around the body. This forces the gas bubbles to dissolve.


DCS may be prevented by:

  • Limiting the depth and duration of deep sea dives
  • Following standard diving guidelines
  • Avoiding diving if you are obese, pregnant, have heart or lung problems, or have had a recent joint or limb injury
  • Avoiding excessive alcohol consumption for 24 hours before diving
  • Avoiding flying for 24 hours after deep sea diving
  • Avoiding repeated dives within a 12 hour period
  • Avoiding flights in nonpressurized aircraft


Divers Alert Network 

Undersea & Hyperbaric Medical Society 


Health Canada 

Nova Scotia Health Authority 


Altitude-induced decompression sickness. Federal Aviation Administration website. Available at: Accessed September 25, 2020.

Decompression illness: what is it and what is the treatment? Divers Alert Network website. Available at: Accessed September 25, 2020.

Decompression illness. EBSCO DynaMed website. Available at:  . Accessed September 25, 2020.

Gertsch JH, Corbett B, Holck PS, et al. Altitude sickness in climbers and efficacy of NSAIDs trial (ASCENT): randomized, controlled trial of ibuprofen versus placebo for prevention of altitude illness. Wilderness Environ Med. 2012;23(4):307-315.

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