Decompression Sickness & HBOT

A diver surfaces feeling tired or unusually sore. A shoulder begins to ache. An arm tingles. Walking feels unsteady. Because the dive appeared routine, it may be tempting to blame dehydration, heavy equipment, seasickness, or simple exhaustion.

Those symptoms should not be ignored.

Decompression sickness is a potentially serious diving and pressure-related injury. If symptoms develop during or after a dive, provide emergency oxygen if trained and equipped to do so, contact emergency medical services, and seek guidance from a dive medicine professional.

Do not wait for symptoms to become severe. Do not fly, travel to altitude, or return to the water in an attempt to relieve symptoms.

CDC guidance identifies early symptom recognition, high-concentration oxygen, medical evaluation, and recompression with hyperbaric oxygen as central parts of decompression-illness care. Divers Alert Network advises contacting emergency services first and DAN afterward, particularly when severe symptoms are present.

What Is Decompression Sickness?

Decompression sickness, commonly called DCS, “the bends,” or caisson disease, can develop when dissolved inert gas forms bubbles in the tissues or bloodstream following a reduction in surrounding pressure.

During a dive, the body absorbs nitrogen or other inert gases from the breathing mixture. As the diver ascends and the surrounding pressure decreases, that gas must leave the body gradually. If decompression is inadequate, bubbles may form and affect joints, skin, blood vessels, the spinal cord, the brain, the lungs, or other tissues.

DCS can occur after a rapid ascent, a deep or prolonged dive, repetitive diving, or air travel too soon after diving. It can also develop following a dive that appeared to remain within accepted limits.

What Does “Decompression Illness” Mean?

Decompression illness is the broader term originally used in Alex’s conditions list. It includes two pressure-related disorders:

Decompression Sickness

DCS results when inert-gas bubbles form in body tissues or blood following a reduction in pressure.

Arterial Gas Embolism

Arterial gas embolism, or AGE, occurs when gas enters the arterial circulation and blocks blood flow. In divers, it may follow pulmonary barotrauma during ascent.

Both conditions can produce neurological symptoms and require urgent medical evaluation. This page focuses primarily on decompression sickness. Medici’s future Gas Embolism & HBOT page should explain AGE in greater detail.

What Are the Symptoms of Decompression Sickness?

Symptoms can be subtle. A person may initially experience only unusual fatigue, mild joint discomfort, tingling, itching, or a vague sense that something is wrong.

Signs and symptoms often begin within 15 minutes to 12 hours after surfacing. They can occur sooner, appear later, or become noticeable after air travel or another increase in altitude.

Pain and Musculoskeletal Symptoms

• Deep or aching joint pain
• Pain in the arms, legs, shoulders, back, or torso
• Muscle discomfort
• Pain that feels unusual compared with normal post-dive soreness

Skin and Circulation Symptoms

• Skin itching
• Blotchy or marbled rash
• Swelling
• Unusual skin color or texture changes

Balance and Ear Symptoms

• Dizziness
• Vertigo
• Ringing in the ears
• Difficulty walking normally
• Loss of balance or coordination

Neurological Symptoms

• Numbness or tingling
• Weakness
• Paralysis
• Confusion
• Personality or behavior changes
• Memory difficulty
• Tremors
• Staggering or abnormal gait
• Difficulty urinating

Breathing and Cardiopulmonary Symptoms

• Shortness of breath
• Chest discomfort
• Cough
• Coughing up bloody or frothy fluid
• Collapse or loss of consciousness

Which Symptoms Require Immediate Emergency Care?

Call 911 for any severe, progressive, neurological, respiratory, or consciousness-related symptoms, including:

• Trouble breathing
• Severe dizziness or vertigo
• Weakness or paralysis
• Abnormal walking or inability to stand
• Confusion or altered behavior
• Loss of consciousness
• Seizures
• Bloody or frothy coughing
• Bladder dysfunction accompanied by neurological symptoms
• Rapidly worsening pain or numbness
• Collapse

A diver with severe DCS should generally be stabilized at the nearest appropriate medical facility before transportation to a hyperbaric chamber. Emergency teams may need to address breathing, circulation, trauma, dehydration, or another medical problem before transfer.

Why Do Divers Sometimes Delay Getting Help?

DCS does not always begin with a dramatic emergency. A diver may think:

• “I probably pulled my shoulder carrying the tank.”
• “The boat ride made me dizzy.”
• “I am just dehydrated.”
• “The dive computer showed no violation.”
• “The tingling went away after oxygen.”
• “I do not want to disrupt the trip.”

Symptoms that improve with surface oxygen can return later. Improvement does not rule out decompression sickness and should not cancel a professional evaluation.

DAN identifies denial and treatment delay as important concerns because initially reversible injury can become more difficult to treat over time.

Can Decompression Sickness Occur After a Safe-Looking Dive?

Yes.

Decompression models and dive computers reduce risk, but they cannot predict every individual response. DCS can occur even when a diver follows an accepted profile.

Risk may be influenced by:

• Deep or prolonged dives
• Repetitive dives
• Rapid ascent
• Missed decompression stops
• Cold water
• Heavy exercise at depth
• Air travel or altitude exposure after diving
• Individual susceptibility
• Illness or physical stress

Hydration and general health are relevant to safe diving, but drinking water does not treat decompression sickness and should never delay emergency evaluation.

What Should You Do While Waiting for Emergency Care?

Administer Oxygen If Trained

Provide the highest concentration of emergency oxygen available within the responder’s training. Oxygen may reduce symptoms and support affected tissues, but it is first aid rather than a substitute for medical evaluation or recompression.

Keep the Diver Under Observation

Monitor breathing, consciousness, coordination, strength, sensation, and symptom progression.

Record the Dive History

When possible, document:

• Depth and duration of recent dives
• Ascent rates
• Decompression stops
• Surface intervals
• Breathing gases
• Time symptoms began
• How symptoms changed
• When and how oxygen was administered
• Any trauma or equipment problems

Arrange Medical Evacuation

Severe cases require EMS and evaluation at an appropriate medical facility.

Contact DAN After EMS

The current DAN emergency hotline is +1-919-684-9111 and is available 24 hours a day. DAN can help patients, dive operators, emergency personnel, and treating clinicians identify appropriate dive-medicine resources.

What Should You Avoid?

Do Not Fly or Travel to Altitude

Reduced cabin pressure or higher terrestrial altitude may worsen bubble formation. A symptomatic diver should be evaluated before flying or ascending to altitude.

Do Not Re-Enter the Water

A diver with suspected DCS should generally be removed from the water and treated on the surface. DAN does not recommend improvised in-water recompression using ordinary air. Specialized in-water protocols require extensive training, equipment, oxygen, support personnel, appropriate conditions, and expert oversight.

Do Not Assume Symptom Relief Means the Emergency Is Over

Oxygen may temporarily reduce symptoms, but they can return.

Do Not Drive Yourself

Dizziness, weakness, confusion, or loss of consciousness may worsen during transportation.

How Is Decompression Sickness Diagnosed?

There is no single home test that can rule decompression sickness in or out.

Diagnosis is based on:

• Recent exposure to diving or increased pressure
• The dive profile
• Timing and progression of symptoms
• Neurological findings
• Physical examination
• Response to oxygen
• Other possible causes of the symptoms

Emergency clinicians may order imaging, blood tests, heart testing, or other studies to evaluate alternative diagnoses or associated injuries. However, normal testing does not automatically exclude decompression sickness.

Consultation with a physician experienced in diving and hyperbaric medicine is often important.

How Is Decompression Sickness Treated?

Initial care may include high-concentration oxygen, stabilization, neurological monitoring, fluids when medically appropriate, and transfer coordination.

The definitive treatment for clinically significant decompression illness is generally recompression with oxygen inside a hyperbaric chamber. The treatment plan depends on the symptoms, neurological findings, response to initial care, delay to treatment, and recommendations of the dive-medicine and hyperbaric teams.

How Does HBOT Help?

During Hyperbaric Oxygen Therapy, the patient enters a medical chamber where pressure is increased under controlled conditions while oxygen is administered.

HBOT may help by:

• Reducing the volume of inert-gas bubbles
• Creating a pressure gradient that supports inert-gas elimination
• Delivering oxygen to tissues affected by impaired blood flow
• Supporting injured neurological and other tissues
• Helping address secondary inflammatory and vascular effects associated with bubbles

Hyperbaric treatment for DCS is often described as recompression therapy because restoring pressure is a central part of treatment.

Emergency-to-HBOT Treatment Pathway

Is Decompression Illness a Recognized HBOT Indication?

Yes.

The Centers for Medicare & Medicaid Services lists decompression illness as one of the covered conditions for chamber-based hyperbaric oxygen therapy under its national coverage determination.

Coverage is not automatic. Payment depends on medical necessity, documentation, Medicare eligibility, the treatment setting, provider requirements, and the patient’s individual insurance benefits.

When Should You Call Medici?

Do not call Medici instead of 911 or delay emergency evaluation while trying to arrange hyperbaric treatment.

Medici Hyperbarics may become part of the care pathway after emergency stabilization when:

• An emergency physician recommends hyperbaric consultation
• A dive-medicine specialist recommends recompression
• The patient has been medically assessed and is stable for transfer
• A hospital or treating provider wants to discuss a physician-directed referral
• Records and the dive history are available for medical review
• A patient needs information about follow-up care after an acute diving injury

Whether Medici can receive a particular referral depends on medical appropriateness, timing, chamber availability, staffing, transfer requirements, the treatment protocol, and the patient’s stability.

For an active diving emergency:

1. Call local emergency services.
2. Provide emergency oxygen if trained and equipped.
3. Contact the DAN emergency hotline at +1-919-684-9111.
4. Follow the instructions of EMS and dive-medicine professionals.

Related Medici Hyperbaric Resources

What Happens After Hyperbaric Treatment?

Some patients improve significantly during or after recompression. Others may require additional chamber treatments, neurological monitoring, rehabilitation, or specialist follow-up.

Residual concerns may include:

• Joint soreness
• Numbness or tingling
• Weakness
• Balance difficulty
• Bladder dysfunction
• Fatigue
• Cognitive or neurological changes
• Reduced confidence returning to activity

Patients with serious neurological DCS may need physical therapy, occupational therapy, neurological care, or other rehabilitation. Permanent symptoms are possible, particularly after severe injury or delayed treatment.

When Can Someone Return to Diving?

A person treated for decompression illness should not decide independently when to return to diving.

The decision depends on:

• Whether symptoms completely resolved
• Whether neurological symptoms occurred
• The severity of the event
• Whether residual deficits remain
• The suspected reason the event occurred
• The patient’s underlying health
• Prior episodes of DCS
• Evaluation by a physician experienced in dive medicine

DAN recommends medical consultation before returning to diving. Patients with severe neurological symptoms or persistent residual symptoms may be advised not to resume diving.

How Can Divers Reduce Their Risk?

No strategy eliminates all risk, but divers can reduce it by:

• Diving within their training and certification
• Following conservative dive profiles
• Monitoring depth, time, and ascent rate
• Completing required decompression and safety stops
• Avoiding rapid ascents
• Using properly maintained equipment
• Remaining rested and medically fit to dive
• Avoiding heavy exertion during demanding dives
• Accounting for cold water and repetitive dive exposure
• Following appropriate surface intervals
• Waiting before flying or traveling to altitude

CDC recommends waiting at least:

• 12 hours after one no-decompression dive
• 18 hours after multiple dives or multiple days of diving
• 24 to 48 hours after a dive requiring decompression stops

These intervals reduce risk but do not eliminate it. A symptomatic diver should be medically evaluated before any flight or altitude exposure.

Frequently Asked Questions

Is Decompression Sickness the Same as “The Bends”?

Yes. “The bends” is a common name for decompression sickness, especially when joint or muscle pain is present. DCS can also affect the skin, balance system, spinal cord, brain, lungs, and circulation.

Is Decompression Illness the Same as Decompression Sickness?

Not exactly. Decompression illness is the umbrella term that includes both decompression sickness and arterial gas embolism. The two conditions can share symptoms and both may require emergency recompression.

Can Decompression Sickness Happen Without Breaking a Dive-Computer Limit?

Yes. Dive tables and computers reduce risk, but no decompression model guarantees that DCS will not occur. Clinical evaluation considers symptoms and the complete dive history, not only whether a computer displayed a warning.

How Soon Do Symptoms Appear?

Symptoms often begin between 15 minutes and 12 hours after surfacing, although they may occur immediately or appear later. Delayed symptoms are less common but can occur, particularly after subsequent altitude exposure.

Should I Still Seek Help if Oxygen Makes the Symptoms Go Away?

Yes. Emergency oxygen can temporarily improve or resolve symptoms, but they may return. A person with suspected DCS should still receive professional evaluation.

Should a Diver Go Directly to the Nearest Hyperbaric Chamber?

Not necessarily.

A person with severe symptoms should generally be stabilized at an appropriate medical facility first. Not every chamber treats diving emergencies, and some facilities may not have the necessary staffing, monitoring, protocols, or emergency capabilities.

Contact EMS first, then DAN or a dive-medicine physician for guidance.

Can a Diver Go Back Underwater to Recompress?

Improvised in-water recompression is not recommended. A symptomatic diver should generally be removed from the water and treated on the surface.

In-water protocols are considered only in specialized remote circumstances with extensive training, oxygen, equipment, support personnel, and medical guidance.

Does Medicare Cover HBOT for Decompression Illness?

CMS lists decompression illness as a covered HBOT condition. Actual payment depends on medical necessity, documentation, eligibility, provider requirements, and the individual plan.

Can Medici Treat an Active Diving Emergency?

Patients should not contact Medici instead of emergency services. Call 911 first and contact DAN after EMS has been activated.

Medici Hyperbarics may discuss physician-directed referral after the patient has been evaluated and stabilized, depending on medical appropriateness and facility availability.

Medical Disclaimer

The information on this page is provided for general education and does not replace emergency medical care, dive-medicine consultation, diagnosis, recompression planning, or individualized treatment.

Decompression sickness and other forms of decompression illness can cause neurological injury, breathing problems, cardiovascular instability, paralysis, permanent disability, or death.

Call 911 for severe, progressive, neurological, respiratory, or consciousness-related symptoms. Administer emergency oxygen only within your training and available equipment. After EMS has been activated, the Divers Alert Network emergency hotline may be reached at +1-919-684-9111.

Do not fly, travel to altitude, return to diving, or attempt improvised in-water recompression after suspected decompression sickness unless specifically directed by qualified dive-medicine professionals.

HBOT candidacy, treatment protocols, transportation decisions, and insurance coverage depend on the patient’s clinical condition, diagnosis, medical stability, timing, facility capabilities, documentation, and physician judgment.

Sources & Further Reading

1. Centers for Disease Control and Prevention, Yellow Book: Scuba Diving: Decompression Illness and Other Dive-Related Injuries. Information about DCI recognition, emergency oxygen, hyperbaric recompression, dive travel, and flying after diving.
2. Divers Alert Network: Decompression Illness. Overview of decompression sickness, arterial gas embolism, symptoms, emergency response, treatment, and return-to-diving considerations.
3. Divers Alert Network: Treating Decompression Sickness. Guidance on emergency oxygen, EMS activation, medical stabilization, dive-history documentation, and avoiding treatment delays.
4. Centers for Medicare & Medicaid Services: National Coverage Determination 20.29, listing decompression illness among the covered conditions for chamber-based HBOT.
5. Undersea & Hyperbaric Medical Society: Decompression Sickness. Clinical explanation of inert-gas bubble formation and pressure-related injury.
6. Divers Alert Network: In-Water Recompression. Safety guidance explaining why symptomatic divers should generally be removed from the water and treated on the surface.

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