Decompression Sickness (DCS)

Diving, like many sports, carries risks and accidents that can occur unexpectedly, no matter how experienced you are. Decompression sickness (DCS), or "the bends", is one such risk. It’s widely dreaded in diving—and for good reason, as it can have severe consequences for divers.

But what exactly is DCS? Breaking it down, here’s a summary of everything you need to know about this condition if you dive—so you’re reminded once again that thorough dive planning is the foundation of safe diving.

What is DCS?

Due to prolonged exposure to pressure or high pressures, the nitrogen in breathing gas is absorbed by tissues, causing saturation. This simply means elevated nitrogen levels in the body, which we mitigate through decompression stops ("deco stops").

How does the body absorb nitrogen?

Nitrogen is highly compressible, losing volume as pressure increases. Simultaneously, the breathing gas becomes denser, multiplying the amount of compressed nitrogen inhaled with each breath, which is then absorbed.

The longer and deeper the dive, the more nitrogen accumulates, eventually saturating tissues.

Why is saturation under pressure a problem?

The issue arises during ascent: as pressure decreases, nitrogen expands, turning saturation into supersaturation—the root cause of DCS.

What are the symptoms?

• Numbness in extremities.

• Mild to severe joint pain (arms/legs), varying in intensity.

• Itching on palms/soles, potentially progressing to other DCS symptoms.

• Rashes, possibly with itching.

• Joint pain.

• Lymph node pain/swelling.

• Head, neck, or torso pain (often indicating severe DCS).

• Slurred speech or language difficulties.

• Neurological issues: weakness, numbness, tightness in limbs, incontinence, stroke-like symptoms.

• "Chokes" (burning chest pain, coughing, breathlessness).

• Staggering (inner ear issues), vertigo, deafness, tinnitus, or vomiting.

How do we prevent it?

Deco stops allow tissues to offgas nitrogen by leveraging higher oxygen levels (the ratio remains, but nitrogen volume decreases per breath). Oxygen traps nitrogen molecules, expelling them during exhalation, gradually reducing nitrogen levels.

There’s no standard deco stop—depth and bottom time dictate it. Hence, dive tables or computers are critical: tables help manually adjust stops, while computers provide real-time depth/duration guidance.

Another (weighty) reason to never dive alone: your buddy can assist during stops or provide emergency air if supplies run low.

Many dives—especially deep ones—exceed no-decompression limits, requiring meticulous surface planning and ample air reserves.

Recreational dives rarely trigger DCS (shorter durations, moderate depths). For example:

• -20m: 45min no-deco time.

• -30m: 20min no-deco time.

At -20m, a 12L tank at 200ATM won’t last 45min (remember to surface at 50ATM). At -30m, deco is almost inevitable—but planned for.





Over half of divers with DCS report symptoms within 1 hour of surfacing; 95% show signs within 6 hours, and nearly all within 24-48 hours.

Free nitrogen bubbles mechanically block blood flow and chemically damage vascular beds.

Any dive accident victim with DCS symptoms (potentially fatal or paralytic) requires emergency medical care and immediate oxygen.

Thus, we stress meticulous dive planning—especially for deep dives. Clarify objectives, roles, and contingency plans to avoid DCS. Dive with experts or clubs (like those here) to ensure safety and unforgettable experiences. Explore, learn, and embrace the ocean’s beauty.

A Miskitu legend in the Caribbean claims DCS occurs when the siren Liwa Mairin stares at you. Whether you believe in myths or fancy spotting a siren mid-dive, plan flawlessly to avoid danger. Now dive in—life’s too short!