Decompression sickness

Overview

Decompression sickness occurs when nitrogen or another inert gas that dissolved in body tissues under increased pressure comes out of solution too quickly as ambient pressure falls. Bubbles can form in joints, skin, veins, spinal cord, brain, inner ear and other tissues. The likelihood rises with greater inert-gas loading and faster or inadequately staged ascent, but cases can occur even after apparently compliant recreational dives. ^{[1] [2]}

Bubble formation can obstruct blood flow, distort tissues and trigger endothelial injury and inflammation. Musculoskeletal disease may present mainly with deep aching pain, while neurologic DCS can affect the spinal cord or brain and produce numbness, weakness, gait disturbance, bladder dysfunction or cognitive change. Pulmonary involvement is uncommon but can produce chest pain, cough and breathlessness. ^{[1] [2]}

The key clinical clue is a new symptom temporally related to diving, compressed-air exposure or another substantial pressure change. Dive computers and tables estimate risk but do not prove or exclude DCS. A benign explanation such as muscle strain may be possible, yet neurologic findings, progressive symptoms, unusual fatigue or symptoms involving more than one system should lower the threshold for emergency consultation with a hyperbaric or dive-medicine service. ^{[1] [2] [3]}

Symptoms and warning signs

Symptoms often begin within hours after surfacing, although onset can be delayed. Deep joint or limb pain, tingling, numbness, weakness, dizziness, imbalance, unusual fatigue, itching or mottled skin can occur. Inner-ear involvement may cause vertigo, hearing change or severe imbalance. A detailed neurologic examination is important because subtle sensory or coordination deficits may be missed by casual observation. ^{[1] [2]}

Weakness, difficulty walking, confusion, loss of consciousness, severe vertigo, new bladder dysfunction, shortness of breath, chest pain or rapidly worsening symptoms after a dive are emergencies. First aid should not delay evacuation. Commercial air travel or ascent to altitude can worsen decompression stress and should generally be avoided until a dive-medicine professional advises otherwise. ^{[1] [2]}

Diagnosis

DCS is primarily a clinical diagnosis based on the dive profile, symptom timing and examination. Clinicians review depth, duration, ascent rate, repetitive dives, omitted decompression, gas mixture, flying after diving and any equipment or breathing-gas problem. A complete neurologic examination should be repeated because signs can evolve. No blood test can reliably rule DCS in or out. ^{[1] [2]}

Imaging and routine laboratory tests are used mainly to investigate complications or alternative diagnoses. MRI can be normal even with neurologic DCS. If arterial gas embolism, pneumothorax, stroke, cardiac ischemia or trauma is plausible, testing follows those emergency pathways. Consultation with a hyperbaric specialist is often more useful than waiting for a confirmatory test that does not exist. ^{[1] [2] [3]}

Alternatives include arterial gas embolism, barotrauma, musculoskeletal strain, immersion pulmonary edema, hypothermia, carbon monoxide contamination, oxygen toxicity, stroke, vestibular disorders and cardiac events. DCS and arterial gas embolism may be grouped clinically as decompression illness because immediate management overlaps, but pulmonary barotrauma and pneumothorax can affect transport and chamber decisions. ^{[2] [3]}

Causes, risk factors and clinical context

Risk rises with deeper and longer dives, repetitive diving, rapid ascent, omitted decompression stops, heavy exertion, dehydration and flying or travelling to altitude soon after diving. Individual susceptibility varies and no dive profile is completely risk free. Previous DCS may prompt evaluation for dive practices and, in selected cases, conditions such as a right-to-left cardiac shunt. ^{[1] [2]}

Early oxygen and recompression can produce rapid improvement, but recovery depends on the organ system involved and treatment delay. Musculoskeletal symptoms often resolve well. Spinal-cord, brain or inner-ear disease may leave residual weakness, sensory loss, balance problems or fatigue. Symptoms can recur after initial improvement, which is why observation and specialist follow-up matter. ^{[1] [2] [3]}

Complications and why the diagnosis matters

Untreated neurologic DCS can cause persistent paralysis, gait impairment, bladder dysfunction or cognitive symptoms. Severe cardiopulmonary decompression illness can threaten life. Recompression itself requires clinical screening because untreated pneumothorax is hazardous in a chamber. Delayed diagnosis may also allow a non-diving emergency such as stroke or acute coronary syndrome to go untreated. ^{[1] [2]}

Most divers treated promptly have a favorable outcome, particularly when symptoms are mild and non-neurologic. Prognosis becomes less predictable with severe neurologic deficits, prolonged treatment delay or recurrent disease. Return to diving is individualized; symptom resolution alone does not automatically mean that immediate return is safe. ^{[1] [2] [3]}

Treatment and management

Give high-concentration oxygen as soon as practical and continue it during evacuation when supplies permit. Position the diver comfortably rather than forcing head-down positioning. Hyperbaric recompression with oxygen is the definitive treatment for significant DCS and should be arranged through an experienced facility. Treatment decisions are based on the clinical syndrome rather than the apparent severity of the dive-profile violation. ^{[1] [2]}

Maintain hydration when the patient can safely drink and use intravenous isotonic fluid when clinically indicated, while avoiding fluid overload. Keep the patient warm, monitor vital signs and perform serial neurologic examinations. Standard emergency care takes priority for airway, breathing and circulation problems. Diving organizations can assist with chamber location and specialist consultation. ^{[1] [2] [3]}

Do not put a symptomatic diver back underwater for improvised “in-water recompression” unless operating under a highly specialized protocol; it can worsen risk and delay definitive care. Do not rely on pain relief after oxygen as proof that the diagnosis was harmless. Suspected pneumothorax requires urgent evaluation before pressurization. ^{[1] [2]}

Follow-up, recovery and prevention

After treatment, follow-up assesses residual neurologic, vestibular, pulmonary or musculoskeletal deficits and determines whether additional recompression is needed. Divers with persistent symptoms may need rehabilitation. A dive-medicine clinician can review the original dive profile, contributing factors and timing of safe return to diving and flying. ^{[1] [2]}

Prevention includes appropriate training, conservative dive planning, adherence to ascent and decompression guidance, avoiding breath-hold ascent during scuba, maintaining equipment, managing hydration and avoiding excessive exertion around ascent. Divers should follow accepted guidance for surface intervals before flying and should not dive when illness or medication makes safe diving uncertain. ^{[1] [2] [3]}

Special situations and care pathway

Pregnancy, significant cardiopulmonary disease, seizure disorders and some medications may affect fitness to dive and require individualized advice. A patent foramen ovale is common in the population and is not routinely sought after every uncomplicated dive, but recurrent or serious neurologic DCS may prompt specialist evaluation of right-to-left shunting. ^{[1] [2] [3]}

Recognize a compatible post-dive syndrome, start high-concentration oxygen, contact emergency and dive-medicine support, document the dive profile and serial neurologic findings, exclude immediately dangerous alternatives, and transfer to a hyperbaric facility when recompression is recommended. Treatment should not be delayed solely to obtain imaging. ^{[1] [2]}

When to seek urgent medical care

Call emergency services for neurologic symptoms, severe vertigo, breathing difficulty, chest pain, loss of consciousness or progressive illness after diving. Even mild unexplained neurologic symptoms after a dive deserve urgent specialist advice because early findings can be subtle. ^{[1] [2]}

Sources

1. CDC Yellow Book — Scuba Diving: Decompression Illness and Other Dive-Related Injuries
2. Divers Alert Network — Decompression Sickness
3. Merck Manual Professional — Decompression Sickness

This article is based on trusted medical sources and is awaiting clinician review. It is not a substitute for personalized medical advice.