DCS — Decompression Sickness

Decompression Sickness (DCS) happens when nitrogen bubbles form in your tissues during ascent. This occurs because the pressure drops too fast for your body to clear the gas.

How bubbles form

Nitrogen enters your blood under pressure. While you dive at 30 m, your body absorbs this gas into various tissues. The risk increases if you stay deep for long periods. You must ascend slowly so that the nitrogen leaves your system through your lungs. If the pressure drops too quickly, the gas forms bubbles in your blood or joints.

Bubbles cause pain. I saw a diver in Koh Tao in 2018 suffer because he ignored his computer’s ascent rate. He ascended from 22 m in under one minute. This mistake caused immediate joint pain.

Symptoms vary widely. Most cases appear within 24 hours after a dive. You might feel it at 15 m depth or during a surface interval. Skin rashes and neurological issues are also common signs.

Planning for safety

Good planning reduces your risk. You should track every minute spent at depth. Nitrogen loading is not a linear process. It depends on how much pressure you experience during the dive. Most dive computers use the Bühlmann ZHL-16C algorithm to calculate these limits.

Stay hydrated. Dehydration increases your risk because it affects how your blood carries nitrogen away from your tissues. I always drink 500 ml of water between dives. This helps maintain proper blood volume.

Avoid flying after diving. You need a surface interval of at least 18 hours before you board a plane. This wait ensures that most residual nitrogen has left your body.

Common mistakes in the field

Many divers ignore small warnings. They think a little joint ache is just tiredness. This is a dangerous assumption. If you feel unwell, use an oxygen kit immediately. Do not wait for symptoms to worsen.

Repetitive diving is another trap. In Komodo, I saw groups do four dives in one day without enough rest. Their nitrogen levels were high because they skipped long surface intervals. This increases the chance of DCS significantly.

Never skip your safety stop. A 3-minute stop at 5 m helps off-gas much more effectively than a direct ascent to the surface. It is a non-negotiable rule for every diver.

Related diving concepts

DCS is closely linked to nitrogen narcosis. Narcosis affects your judgment while you are at depth. If you feel “drunk” at 35 m, you might make mistakes with your air or ascent rate. This confusion often leads to the fast ascents that cause DCS.

You should also understand bends vs. chokes. The “bends” refers to joint pain from bubbles. “Chokes” involves bubbles in the lungs and is much more severe. Both require immediate medical attention and pure oxygen.

Check your gear. A faulty regulator can cause rapid depth changes if it malfunctions. Always monitor your depth gauge closely during every descent and ascent.