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Understanding and managing Decompression Sickness: A guide for divers


decompression sickness

Today, we’re delving into decompression sickness (DCS) because it isn’t always explained well in some introductory courses. Recognizing the signs and symptoms of decompression illness and knowing what to do is crucial for every diver. The more divers are aware of these issues, the better prepared we all are.

This post is sponsored by While I hope you’re not reading this in an emergency, I’ll cover all the important information before telling you about today’s sponsor.


What is Decompression Sickness?

Decompression Sickness (DCS), also known as ‘the bends’, describes a variety of injuries resulting from inadequate decompression following exposure to increased pressure. This can occur even after uneventful dives within accepted no-decompression limits but is more likely after rapid underwater ascents. DCS can also be prompted by ascending in an airplane or up a mountain too soon after diving, as the pressure around you drops.

Simple Explanation: As you breathe gas underwater, the increased water pressure causes more of the gas to be absorbed into your body tissues. If you ascend too quickly, this gas doesn’t have time to work its way out slowly, forming bubbles in your bloodstream and tissues. These bubbles can block blood vessels and organs, causing various symptoms based on their location.

Symptoms of DCS

Symptoms of DCS can occur immediately after surfacing or up to 24 hours later, typically appearing between 15 minutes and 12 hours post-dive. They vary between divers and can sometimes be mundane, leading divers to overlook them. Here are some key symptoms to watch for:

  • Unusual Fatigue: Common and often mistaken for normal tiredness after a dive.
  • Itchy Skin: May indicate subcutaneous emphysema where bubbles form under the skin.
  • Joint and Muscle Pain: Pain in the arms, legs, or torso is a classic symptom.
  • Dizziness and Vertigo: If you feel woozy, secure anything you’re carrying and lay down.
  • Ringing in the Ears: Can be mistaken for equalization issues but may signal DCS.
  • Numbness, Tingling, and Paralysis: Serious symptoms that require immediate attention.
  • Shortness of Breath: Indicates a serious issue; seek help immediately.
Decompression sickness
Keep detailed notes on symptoms and signs of DCS

Recognizing Signs of DCS

Signs are what you can observe in yourself or other divers:

  • Blotchy Rash: Often accompanies itchy skin.
  • Muscle Weakness or Paralysis: Struggling with tasks that are usually easy.
  • Staggering or Unsteady Walk: Could indicate numbness or vertigo.
  • Mental Confusion or Personality Changes: Note any bizarre behavior.
  • Difficulty Urinating: Should not be ignored if it occurs after a dive.
  • Coughing Blood or Frothy Sputum: Severe sign requiring immediate action.
  • Collapse or Unconsciousness: Indicates a critical situation.

How to Treat a Diver with Suspected DCS

If a diver shows symptoms of DCS, follow these steps:

  1. Administer Emergency Oxygen: Most dive boats have an oxygen kit onboard. Use it to provide 100% oxygen until emergency services take over.
  2. Determine Severity:
    • Emergency DCS: Symptoms like dizziness, intermittent consciousness, weakness, abnormal gait, or trouble breathing. Provide oxygen and arrange emergency evacuation.
    • Urgent DCS: Severe, constant pain. Administer oxygen and fluids. Contact DAN or a medical facility.
    • Timely DCS: Vague pain or sensations. Conduct a neurological evaluation and seek medical advice.
Decompression sickness
Oxygen is one of the key treatments for DCS

Neurological Examination for DCS

Conduct a neurological exam if time allows and the diver is capable:

  1. Orientation: Ask the diver their name, age, location, and current time or date.
  2. Eyes: Check the diver’s ability to count fingers, follow your hand with their eyes, and check for equal pupil size.
  3. Face: Observe for symmetrical facial expressions and muscle contractions.
  4. Hearing: Evaluate hearing by rubbing fingers together near the diver’s ears.
  5. Swallowing Reflex: Watch the diver swallow to ensure proper movement.
  6. Tongue: Have the diver stick out their tongue to see if it comes out straight.
  7. Muscle Strength: Test shoulder, arm, and leg strength for equality on both sides.
  8. Sensory Perception: Lightly touch the diver’s skin to check for equal sensation.
  9. Balance and Coordination: Have the diver walk heel-to-toe, balance with eyes closed, and perform coordination tasks like touching their nose with their finger.

Denial: The Worst Symptom of DCS

Denial is arguably the worst symptom of DCS. Delayed treatment can lead to permanent injury and prolong (or even prevent) the diver’s full recovery. Always contact DAN or a medical professional with training in dive medicine in cases of suspected DCS, even if the symptoms and signs appear to have resolved.


Decompression sickness is tough because the symptoms are broad, and there is no definitive correlation between signs and symptoms for different divers. The key to the best outcome is administering oxygen, calling for help as soon as possible, and taking notes to save time. Thanks for reading, everybody, and safe diving!

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Picture of Mark Evans
Mark Evans
Scuba Diver's Editorial Director Mark Evans has been in the diving industry for nearly 25 years, and has been diving since he was just 12 years old. nearly 40-odd years later and he is still addicted to the underwater world.
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