Decompression Sickness Prevention: What Every UK Diver Needs to Know

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Decompression sickness, the bends, DCS. Whatever you call it, the result is the same: dissolved nitrogen forming bubbles in your blood and tissues, causing anything from joint pain to paralysis to death.

UK divers face higher DCS risk than tropical divers at identical depths and profiles. Understanding why, and how to prevent it, might save your diving career or your life.

How Decompression Sickness Happens

Compressed air at depth contains nitrogen your body absorbs. The deeper you dive and longer you stay, the more nitrogen dissolves into your blood and tissues.

Ascend too quickly and that dissolved nitrogen cannot off-gas safely. Instead, it forms bubbles. Tiny bubbles cause joint pain. Larger bubbles block blood flow. Bubbles in nervous tissue cause paralysis or death.

Your dive computer or tables tell you how fast you can ascend based on how much nitrogen you've absorbed. Exceed those limits and you risk DCS.

Why Cold Water Increases DCS Risk

Cold water affects nitrogen absorption and elimination through several mechanisms.

Peripheral vasoconstriction reduces blood flow to your extremities. During descent, your cold fingers and toes still absorb nitrogen, but the reduced blood flow means slower absorption. During ascent, vasoconstriction persists. Your tissues cannot off-gas nitrogen efficiently.

Cold stress increases breathing rate by 30-50%. More breathing means more nitrogen absorbed. Shivering increases metabolic rate and changes circulation patterns, affecting nitrogen transport.

The net result: Studies show 50-100% higher DCS incidence in water below 15°C compared to warm water for identical dive profiles.

Every UK dive carries higher DCS risk than the tropical equivalent.

Preventing DCS: The Basics

Follow your computer or tables without negotiation. Your computer calculates no-decompression limits based on depth and time. Stay within those limits. If your computer says ascend, ascend.

Ascend slowly. Maximum rate 9m/minute, ideal 6m/minute. Slow ascent allows nitrogen to off-gas gradually rather than forming bubbles.

Safety stops: 3-5 minutes at 5m depth even when not required by your computer. This provides massive DCS protection margin.

Surface interval before flying: 12 hours minimum after single dive, 18 hours after multiple dives, 24 hours after decompression diving. Flying too soon after diving reduces ambient pressure, causing nitrogen bubbles to form even if you were within limits.

Cold Water DCS Prevention

For UK diving specifically, add these protocols:

Use conservative computer settings. Most dive computers allow conservatism adjustment. Set it one or two levels more conservative than default. This shortens your no-decompression limits slightly but provides cold water safety margin.

Extend safety stops. If your computer calls for 3-minute safety stop, do 5 minutes. If it doesn't require a stop, do one anyway. The extra decompression time costs nothing and prevents DCS.

Avoid yo-yo profiles. Multiple depth changes during a dive (descending and ascending repeatedly) confuse nitrogen calculations and increase DCS risk. Dive the deepest part first, then gradually shallower.

Don't dive multiple days without rest. UK divers doing weekend trips (4-6 dives over 2 days) build significant nitrogen loading. Skip the last dive if you're tired. Take a no-dive day between weekends.

Hydration and DCS

Dehydration thickens your blood, impairing nitrogen off-gassing and significantly increasing DCS risk.

Drink water before diving. 500ml minimum 30 minutes before your dive. Drink between dives. Avoid alcohol the night before diving and definitely avoid drinking between dives.

UK diving involves substantial physical exertion (gearing up in thick exposure suits, shore entries, boat exits in rough seas). This exertion causes dehydration even in cold weather.

Signs of dehydration: dark urine, headache, dry mouth, fatigue. If you're dehydrated, skip the dive.

Recognising DCS Symptoms

Early symptoms appear 1-6 hours after diving, though onset can be delayed up to 24 hours.

Mild DCS: Joint pain or aching (knees, elbows, shoulders most common), unexplained fatigue, itchy skin or rashes, headache.

Severe DCS: Numbness or tingling (especially limbs), difficulty breathing, dizziness or vertigo, confusion or personality changes, paralysis, loss of consciousness.

Never ignore mild symptoms thinking they'll pass. Untreated DCS worsens. Delayed treatment means worse outcomes.

What to Do If You Suspect DCS

If you or your buddy shows DCS symptoms: Stop all activity. Lie flat (horizontal position prevents bubbles moving to brain). Breathe 100% oxygen if available (massively improves outcomes). Drink water (if conscious and not vomiting). Call for help immediately.

DAN Europe 24/7 emergency hotline: +44 7740 251 635. They'll coordinate your treatment and nearest recompression chamber.

UK recompression chambers: Limited locations (London, Portsmouth, Aberdeen, Gosport, Plymouth). DAN will arrange transport.

Time matters critically. Hyperbaric treatment within 6 hours has excellent outcomes. Treatment delayed beyond 24 hours has poor outcomes.

Never "wait and see" with suspected DCS. The cost of being wrong is permanent disability or death.

Risk Factors Beyond Cold

Age over 40 increases DCS risk. Obesity increases risk (nitrogen dissolves in fat, obese divers carry more nitrogen). Dehydration (already discussed). Patent foramen ovale (hole in heart present in 25% of people, allows nitrogen bubbles to bypass lungs).

Strenuous exercise immediately after diving increases circulation and bubble formation. Rest for 2-3 hours post-dive before heavy exercise.

Multiple dives per day compound nitrogen loading. If doing repetitive dives, make each dive progressively shallower (deep dive first, shallow dive last).

Nitrox and DCS

Enriched air nitrox (higher oxygen, lower nitrogen than regular air) reduces nitrogen absorption, lowering DCS risk for a given depth.

UK wreck diving often uses EAN32 (32% oxygen) for this reason. At 30-40m wreck depths, nitrox provides longer bottom time and lower DCS risk.

However, nitrox has maximum operating depth limits. Dive deeper than your MOD and you risk oxygen toxicity.

The Conservative Approach

Some divers push their computers to the limit on every dive. They surface with 1-2 minutes of no-decompression time remaining.

Don't be that diver in UK waters.

Build conservatism into everything. Use conservative computer settings. Extend safety stops. Leave substantial no-decompression margin. Skip the last dive if tired.

DCS can end your diving permanently. Preventing it is worth sacrificing a few minutes of bottom time.

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