Decompression Sickness Explained

Decompression Sickness Explained

Every diver, from novice to experienced, learns about decompression sickness, or DCS. It is a fundamental part of our dive training, often discussed with a degree of seriousness that underscores its importance. But what exactly is DCS, what causes it, and most crucially, how do we prevent it? Let us delve into the science behind this condition, ensuring we are all better equipped to enjoy our underwater adventures safely.

What Causes Decompression Sickness?

The root cause of DCS lies in the physics of gases under pressure. When we descend into the water, the ambient pressure increases. Our bodies, primarily water, absorb inert gases from the air we breathe, mainly nitrogen, in proportion to this increased pressure. Think of it like a fizzy drink bottle: when sealed under pressure, the carbon dioxide dissolves into the liquid. The deeper and longer we dive, the more nitrogen our tissues absorb.

The problem arises when we ascend. As the pressure decreases, the dissolved nitrogen wants to come out of solution. If the ascent is too rapid, or if we have absorbed too much nitrogen for a given ascent rate, the nitrogen can form bubbles in our tissues and bloodstream. These bubbles are the culprits behind DCS.

Imagine opening that fizzy drink bottle too quickly. The sudden release of pressure causes the dissolved gas to rapidly come out of solution, creating a cascade of bubbles. In our bodies, these bubbles can cause a variety of issues, depending on where they form.

Symptoms of Decompression Sickness

DCS symptoms can be incredibly varied, ranging from mild discomfort to severe, life-threatening conditions. The type and severity of symptoms depend on the number, size, and location of the nitrogen bubbles. Symptoms can appear immediately after a dive, or several hours later, typically within 24 hours.

Common symptoms include:

• Joint Pain (The Bends): This is perhaps the most well-known symptom, often affecting the elbows, shoulders, hips, and knees. The pain can range from a dull ache to an excruciating throb.
• Skin Rash or Itching: Often described as a mottled or marbled appearance, sometimes accompanied by itching.
• Fatigue: Unusual or extreme tiredness that is disproportionate to the dive activity.
• Neurological Symptoms: These are more serious and can include:
  • Numbness or tingling
  • Muscle weakness or paralysis
  • Dizziness or vertigo
  • Headache
  • Vision disturbances
  • Difficulty with balance or coordination
  • Confusion or personality changes
• Pulmonary Symptoms (The Chokes): While less common, bubbles in the lungs can cause coughing, chest pain, and difficulty breathing.
• Circulatory Symptoms: In severe cases, bubbles can affect the heart and circulatory system, leading to shock.

It is crucial to remember that any unusual symptom after a dive should be considered potential DCS until proven otherwise. Do not dismiss symptoms, even if they seem minor.

Prevention is Key

Preventing DCS is paramount, and thankfully, modern dive practices and technology make it highly achievable. Our training covers the fundamental principles, and adhering to them is our best defence.

• Plan Your Dive, Dive Your Plan: Always plan your dive thoroughly, considering depth, bottom time, and your gas consumption. Stick to your plan.
• Stay Within No-Decompression Limits: Use your dive computer or dive tables to stay well within the no-decompression limits for your planned depth and time. These limits are conservative by design.
• Ascend Slowly: A slow ascent rate is critical. Most agencies recommend no faster than 18 metres per minute. Your dive computer will typically monitor and alert you to your ascent rate.
• Perform Safety Stops: A safety stop, typically for 3-5 minutes at 5 metres, allows for additional off-gassing of nitrogen before surfacing. Even if your computer does not require one, it is always a good practice.
• Avoid Repetitive Deep Dives: Multiple deep dives within a short period increase your nitrogen load. Be mindful of surface intervals and cumulative nitrogen absorption.
• Stay Hydrated: Good hydration is thought to aid in off-gassing and circulation.
• Avoid Strenuous Exercise Before or After Diving: Physical exertion can influence nitrogen uptake and release.
• Be Mindful of Flying After Diving: The decrease in atmospheric pressure during air travel can exacerbate nitrogen off-gassing, increasing DCS risk. Allow sufficient surface interval before flying, typically 12-18 hours depending on your dive profile. Learn more about dive planning and safety considerations in our diving guides.
• Maintain Good Physical Fitness: While not a direct prevention, a healthy body generally copes better with the physiological stresses of diving. You can find out more about dive fitness on our knowledge base.

Always dive conservatively. If your computer suggests you are close to a no-decompression limit, err on the side of caution and end the dive or ascend to a shallower depth.

Treatment for Decompression Sickness

If you suspect DCS, immediate action is vital. The primary treatment for DCS is recompression in a hyperbaric chamber. This involves placing the diver in a sealed chamber where the pressure is increased, forcing the nitrogen bubbles back into solution. The pressure is then slowly reduced over several hours, allowing the nitrogen to off-gas safely. Oxygen is also administered to aid in off-gassing and tissue recovery.

If DCS is suspected:

• Administer 100% Oxygen: On the surface, if available, administer 100% oxygen via a non-rebreather mask. This is a crucial first aid step.
• Contact Emergency Services: Immediately call for emergency medical assistance and inform them of suspected DCS.
• Transport to a Hyperbaric Facility: Arrange for transport to the nearest hyperbaric chamber.
• Keep the Diver Lying Down: Position the diver lying down, ideally on their side if they are nauseous, and keep them warm.

Early treatment significantly improves the outcome. Never attempt to re-enter the water to self-treat DCS; this is extremely dangerous and ineffective.

Understanding decompression sickness is a fundamental part of responsible diving. By respecting the physics, planning our dives carefully, and adhering to safe diving practices, we can minimise the risk and continue to explore the underwater world with confidence and enjoyment. Remember, this information is for general knowledge and not a substitute for professional medical advice. Always consult a dive physician for personal health concerns related to diving.