Decompression Sickness (The Bends) and Hyperbaric Oxygen Therapy

Decompression sickness (DCS) — commonly called the bends, diver’s disease, or decompression illness — is a range of symptoms that occur when a person experiences a rapid drop in surrounding pressure, usually from a fast or emergency ascent while diving, and sometimes in aviators and astronauts. It shares its root cause and its treatment with arterial gas embolism, and together the two are the reason the hyperbaric chamber was invented.

What causes decompression sickness?

Under pressure at depth, a diver’s tissues absorb extra inert gas — mainly nitrogen — dissolved in the blood and tissues. If the diver ascends slowly, that gas is carried back to the lungs and exhaled harmlessly. But if pressure drops too quickly, the dissolved gas comes out of solution as bubbles inside the body, exactly like opening a shaken bottle of soda. Those bubbles obstruct blood vessels and press on tissues, causing the symptoms of DCS.

Several secondary factors raise the risk: dehydration, fatigue, cold, strenuous exertion, alcohol, excess body weight, older age, and repeated or deep dives without adequate surface intervals.

Symptoms of the bends

DCS is traditionally divided into two types:

• Type I (milder): joint and muscle pain (the classic “bends”), skin itching or mottling, and fatigue.
• Type II (serious): neurological symptoms — numbness, weakness, paralysis, dizziness, difficulty breathing, confusion, or bladder problems. These are emergencies.

Symptoms usually appear within minutes to hours of surfacing. Because Type II can progress, any diver with new neurological symptoms after a dive needs urgent evaluation.

How hyperbaric oxygen therapy treats DCS

The definitive treatment is recompression in a hyperbaric chamber while breathing 100% oxygen. Raising the pressure again shrinks the bubbles so they redissolve and circulation is restored. Breathing pure oxygen at that pressure does two things at once: it relieves the tissue hypoxia caused by the blockage, and it creates a steep gradient that washes nitrogen out of the bubbles and the body far faster than breathing air would. Standardized hyperbaric oxygen treatment tables guide how deep and how long each recompression runs.

As with embolism, early treatment gives the best outcome — but recompression can still help even hours later, so a diver with suspected DCS should always be evaluated at a hyperbaric facility.

Prevention

DCS is largely preventable: ascend slowly, make required safety stops, stay within dive-computer limits, allow adequate surface intervals between dives, stay hydrated, and avoid flying too soon after diving. Good habits at depth are far easier than treatment at the surface.

For detailed medical information, please consult with a qualified healthcare professional.