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Scuba Safety: Decompression Sickness

Scuba Safety: Decompression Sickness

Over on our Girls that Scuba Facebook group we have started a new series called ‘Safety Sunday” where every other Sunday our resident safety diver and GTS moderator Chloe Strauss creates a post on a popular safety topic that comes up again and again and explains more about it. This particular topic about the quarter back turn gained a lot of attention and a lot of members thanking Chloe for the amazing information, so we wanted to share it further and hope you all learn something too!

Please note Chloe is NOT a medical professional, but in writing this post she has consulted with the Divers Alert Network!

Check out our last safety article: Breathing off both regulators

Decompression sickness

DCS occurs in scuba as a result of inadequate decompression of bodily gases after exposure to increased pressure while diving. Let’s assume for the purpose of this post, and for simplicity’s sake, that we are diving on air. The air we breathe (and the air that is in our cylinders) is roughly 78% nitrogen and 21% oxygen. As you breathe this air under pressure, your body absorbs nitrogen in proportion to the pressure you experience. This usually only presents a problem during inadequate decompression following exposure to increased pressure, such as during an ascent or flying after diving. Simply, the process of decompression at a physiological level happens when the partial pressure of dissolved gas in the body is higher than the partial pressure of gas in the lungs. The tissues become supersaturated and the gas molecules pass into the lungs and to be exhaled. At times, bubbles will form in supersaturated tissues (think about shaking a bottle of soda and then opening it). These bubbles can form anywhere in the body, but commonly in the joints resulting in pain, which is where the term “the bends” originates. Divers may also have “silent” bubbles, which do not cause symptoms, and will usually travel through the right heart and into the blood vessels of the lungs, where they are slowly eliminated.

Types of Decompression sickness

There are two types of DCS. Type 1 usually consists of musculoskeletal pain and mild skin symptoms like itching and mild rashes, swelling and pain in tissues surrounding lymph nodes.

Type 2 falls into three categories: neurological, inner ear, and cardiopulmonary. 

  • Neurological symptoms include numbness, tingling, muscle weakness, difficulty walking, problems with coordination or bladder control, and confusion. 
  • Inner-ear symptoms include ringing in the ears, hearing loss, dizziness, nausea, vomiting, and impaired balance. 
  • Cardiopulmonary symptoms include a dry cough, chest pain, and difficulty breathing.

Type 2 symptoms can develop quickly or slowly. A slow build can actually make the diver think the situation is not as serious as it is. Weakness and fatigue are common and can be easy to ignore, especially if they want to keep diving.

Risk factors for DCS


Exercise during a dive can increase the risk of DCS, and exercise during descent and the deepest part of your dive can increase the amount of gas dissolved in tissues. Exercise immediately after a dive can stimulate bubble formation.

Thermal stress

A warmer body can absorb more gas and release it more easily. A cooler body absorbs less gas during descent and releases less during ascent. Quickly rewarming after dive, like getting in a hot tub, could provoke DCS.

Flying after diving 

The pressure in an airplane cabin is lower than on the ground, which could cause issues with DCS. Guidelines for flying after diving can be found on the back of your dive table.


Being in poor health and physical fitness can increase your risk of getting DCS. Dehydration can also increase your risk of DCS. It should be noted that dehydration is thought to predispose an individual to DCS because gas elimination will be less effective.

Read also: 5 things NOT to do after diving

Next time we will talk about the reason that the Divers Alert Network doesn’t give out chamber locations, and what the process of being diagnosed DCS looks like. Please tell me your comments or questions below!