Health conditions

Decompression illness

What is decompression illness?

Decompression illness (DCI) usually refers to one of 2 related conditions and both are most commonly associated with scuba and deep sea divers.

When underwater, divers breathe compressed air that contains nitrogen gas at the same pressure as the surrounding water. This accumulates in the diver's body tissue, and is breathed out on ascent, providing that ascent occurs at a safe rate.

When a diver swims to the surface too quickly (a rapid ascent), the nitrogen can form tiny bubbles in the blood and/or body tissues, causing decompression sickness (DCS).

DCS may occur even if a person dives within the limits of their dive computer or decompression tables and even if they complete a safety stop.

If a diver swims to the surface too quickly, and holds their breath while doing so (a rapid breath hold ascent), the resulting reduction in the ambient pressure can cause their lungs to over-inflate. This can cause the lung’s tiny air sacks to rupture, allowing air bubbles to escape directly into the blood stream. These air bubbles can block the flow of blood to different parts of the body, which is called arterial gas embolism (AGE).

How do you get DCI?

Diving is the most common cause of DCI in Western Australia.

It can also occur in aviators and astronauts.

Signs and symptoms

The symptoms of DCI may include:

  • fatigue
  • joint and muscle aches or pain
  • clouded thinking
  • numbness
  • weakness
  • paralysis
  • rash
  • poor coordination or balance.

Unusual symptoms occurring within 48 hours after diving should be presumed to be DCI until proven otherwise. The onset of DCI symptoms after 48 hours is unusual unless provoked by ascent to altitude, that is flying

What is the first aid for someone with DCI symptoms?

Divers with suspected DCI should be kept lying flat and given oxygen if it is available. All other normal first aid measures should be taken as required.


Hyperbaric oxygen therapy is used to treat DCI.

How does hyperbaric oxygen therapy work for DCI?

Hyperbaric oxygen therapy does four things:

  • compresses the bubbles (shrinks them)
  • increases the rate at which nitrogen is removed from the body
  • reduces the inflammation created by the bubbles
  • improves the oxygen supply to body tissue.

While being treated for DCI

It is important you rest and drink lots of fluids. Alcohol should be avoided as it can cause dehydration.

If you have aches and pains between your hyperbaric treatments you can take paracetamol or an anti-inflammatory drug, such as aspirin or ibuprofen.

You should continue taking any normal medications as prescribed.    

How can decompression illness be prevented?

How to prevent a recurrence:

  • Use dive tables even if you use a dive computer.
  • Dive only if you feel well.
  • Drink lots of fluids before and after the dive.
  • Know your diving equipment and keep it well serviced.
  • Avoid strenuous exercise and heavy alcohol consumption immediately after diving.
  • Allow a safe surface interval between dives (ideally 2 hours).

Multiple dives on the same day and yo-yo diving (a series of dives that have short periods of time at depth alternating with similar short periods at the surface) increases your risk of DCI.

One third of divers who develop DCI are within dive table limits, so be conservative.

When is it safe to dive again?

Do not dive for 1 month after treatment as the risk of recurrence is more likely.

Further diving following significant neurological DCI is best avoided.

What about flying after decompression illness?

Flying or climbing to an altitude greater than 300m should be avoided for 4 to 6 weeks to avoid recurrence of symptoms.

Where to get help

  • Always dial triple zero (000) to call an ambulance in a medical emergency.
  • See your doctor.
  • Visit a GP after hours.
  • Ring healthdirect Australia on 1800 022 222.
  • Contact Fremantle Hospital Hyperbaric Unit on 9431 2233 during opening hours or via 9431 3333 after hours.


  • The symptoms of DCI may include fatigue, joint and muscle aches, cloudy thinking, numbness and weakness.
  • Unusual symptoms after diving should be presumed to be DCI until proven otherwise.
  • Divers with suspected DCI should be kept lying flat and given oxygen if it is available. All other normal first aid measures should be applied as required.


Fremantle Hospital and Health Service

This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.

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