Tuesday January 28 2020
September 12, 2013

Decompression: Sickness or Illness?

I am always asked about these two terms when I meet non-divers or in my Open Water Diver classes. It is known that “decompression” is something bad and related to diving. It is one of the topics everybody is familiar, however minority of them really know what decompression is. In most languages (in Turkish for example), “illness” and “sickness” refer to the same word. But in fact, decompression sickness and decompression illness are different but related.

Decompression Illness (DCI)

Decompression Illness comprises both Decompression Sickness (DCS) and Arterial Gas Embolism (AGE). Decompression Illness (DCI) is a word for these two diseases caused by decreased surrounding pressure. To be able to understand Decompression Illness (DCI), we should both talk about Decompression Sickness (DCS) and Arterial Gas Embolism (AGE).

Decompression Sickness (DCS)

A scuba diver is inhaling pressurized air from the air source (tank). When it gets deeper, pressure and coldness increase. When a diver is at 10 meters, surrounding pressure is doubled with respect to the surface. Nitrogen, which a diver gets from the air he/she is breathing becomes liquid because of the pressure and cold.

Think about coke. It says “drink cold” on the bottle. Because the gas in the coke dissolves better in cold and tastes better. There is also pressure in the bottle. When you open the cover of the bottle, dissolved gas in coke turns into bubbles and tries to fly away from the bottle.

It is the same logic for a diver who ascends fast to the surface. Nitrogen in the blood and tissues turns into gas format as bubbles. These bubbles obstruct the veils and stop the blood flow. This may occur in brain or in heart which can be very dangerous and even mortal.

Rapid ascend is one of the reasons for Decompression Sickness (DCS). Another reason is exceeding the dive limits. These dive limits are set for safety and can be calculated by using dive tables and dive computers. There are certain limits for each depth. For example, according to SSI Dive Table, a diver diving to 18 meters can stay at that depth no longer than 50 minutes. After 50 minutes, the diver is under the risk of Decompression Sickness (DCS).

Precaution For Decompression Sickness (DCS)

  • Don’t ascent faster than 9 meters/minute
  • Don’t exceed the dive limits

Some Symptoms and Signs of Decompression Sickness

  • Fatigue
  • Joint pain
  • Change in personality
  • Coughing
  • Paralysis
  • Difficulty in breathing
  • Chest pain
  • Dizziness
  • Itchiness
  • Nausea
  • Unconsciousness

First Aid and Treatment for Decompression Sickness (DCS)

First aid for decompression sickness is to supply 100% oxygen to the victim. This will help some of the nitrogen bubbles to go out. Some non-alcohol drinks and Aspirin can also be helpful.

Treatment can only be done in Decompression Chamber. Decompression Chamber is a small cylindrical room. Victim gets in and the pressure is increased, making the nitrogen bubbles turn back into liquid again. Then the pressure is decreased slowly, taking nitrogen out of victim’s body (by breathing) without becoming bubbles. In Decompression Chamber, the victim breaths 100% oxygen.

Arterial Gas Embolism (AGE)

Arterial Gas Embolism (AGE) is mostly a result of ascend without continuous breathing. If a diver doesn’t exhale during the ascend, his/her lungs will be forced. Because the lungs trap air inside if the diver holds air. This air’s volume will increase with the decreasing surrounding pressure during the ascend. As a result, lungs will “rend“. This is called pulmonary barotrauma.

Imagine a balloon at 10 meters of depth, filled with air. If you release that balloon, it will start to ascend. From 10 meters to the surface (0 meters), the volume will double. If the balloon isn’t elastic enough, it will blow! This is exactly the same if a diver doesn’t exhale during an ascend, because our lungs are just like balloons, trapping air inside.

The air inside the diver’s “rend” lung will now release and it will reach the circulation system. Even a very small air (gas) bubble reaches the circulation system, it can give huge amount of damage to the body. Since our brains need most of the blood because of the oxygen need, this small bubble may block circulation in there. Of course, it is the same for heart.

This is why Arterial Gas Embolism (AGE) is the most curious type of Decompression Illness (DCI).

Precaution for Arterial Gas Embolism (AGE)

  • Never hold your breath during the dive (especially while ascending)

Some Symptoms and Signs of Arterial Gas Embolism (AGE)

  • Chest pain
  • Dizziness
  • Death
  • Convulsion
  • Paralysis
  • Disorientation

First Aid and Treatment for Arterial Gas Embolism (AGE)

Just like Decompression Sickness (DCS), Arterial Gas Embolism (AGE) also requires 100% oxygen as first aid and Decompression Chamber for recompression. Most of the signs and symptoms may disappear after oxygen aspiration for both diseases. But even if this happens and the victim doesn’t demand treatment, there is still an obvious need for treatment. The victim should be taken to a dive physician for treatment.

If I sum up, Decompression Illness (DCI) consists of two diseases: Decompression Sickness and Arterial Gas Embolism. Decompression Sickness (DCS) may become a result of rapid ascend and exceeding the dive limits (also called Non-Decompression Limits). Liquid nitrogen turns into gas format as bubbles because of the sudden pressure change. Pure oxygen for first aid, Decompression Chamber for treatment needed.

Arterial Gas Embolism (AGE) may become a result of holding air while ascending during a dive. Our lungs expand due to the volume increase while ascending and if not exhaled, lungs may explode. Air in lungs reaches the circulation system and these small bubbles may block the blood flow. Just like Decompression Sickness (DCS), Arterial Gas Embolism (AGE) requires a first aid by providing pure oxygen and a treatment by Decompression Chamber.

I advise you a great article about Decompression Illness from Divers Alert Network‘s web-site here.

You can also read the “Risks of Diving Page” here on Dive With Seaman.

Be a S.A.F.E. (slowly ascend from every dive) diver and never ever hold your breath during your dives.


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About Seaman


Hi, my name is Murat Demirağ. I have been diving since 1996 and teaching scuba since 2005. I wanted to share my knowledge through divewithseaman.com

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