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# Decompression sickness and diving injuries

Illness when gas bubbles form in the body after a dive or a fast rise in altitude, causing joint pain, numbness or paralysis. Treated in a hyperbaric chamber.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Spinal cord](https://durgical.com/en/anatomy/spinal-cord/)
- [Grey matter of the cord](https://durgical.com/en/anatomy/grey-matter-of-spinal-cord/)
- [Anterior spinal artery](https://durgical.com/en/anatomy/anterior-spinal-artery/)
- [Pleura](https://durgical.com/en/anatomy/pleura/)
- [Pulmonary veins](https://durgical.com/en/anatomy/pulmonary-veins/)
- [Left ventricle](https://durgical.com/en/anatomy/left-ventricle/)
- [Eardrum](https://durgical.com/en/anatomy/tympanic-membrane/)
- [Maxillary sinus](https://durgical.com/en/anatomy/maxillary-sinus/)

## Why it happens

- [Fat, air and amniotic fluid embolism](https://durgical.com/en/general-pathology/fat-air-and-amniotic-fluid-embolism/)
- [Diving, decompression and hyperbaric oxygen](https://durgical.com/en/physiology/diving-decompression-and-hyperbaric-oxygen/)

## What it is

Decompression illness covers two bubble disorders of divers and others exposed to pressure changes: decompression sickness, where dissolved nitrogen forms bubbles in tissues and blood during or after ascent, and arterial gas embolism, where lung overexpansion pushes air into the arteries. Diving also causes barotrauma of the ears, sinuses and lungs from pressure differences in air spaces.

## Who gets it

Recreational diving is popular on Colombia's Caribbean coast (San Andrés, Providencia, Santa Marta, Cartagena) and Pacific coast. Decompression sickness is uncommon in recreational divers but frequent among artisanal lobster and fishing divers in the Caribbean who make repeated deep dives with little training. It also affects tunnel workers, pilots and astronauts. Hyperbaric chambers are few, so evacuation is often long.

## Causes

- Ascent too fast or missed decompression stops
- Deep, long or repeated dives
- Flying or driving over high mountains soon after diving
- Breath-holding during ascent with compressed air (lung overexpansion, arterial gas embolism)
- Pressure changes in the middle ear, sinuses or lungs (barotrauma)

## Risk factors

- Patent foramen ovale or other right-to-left shunt
- Dehydration, fatigue, cold water and heavy exertion
- Obesity and older age
- Lung disease with air trapping (asthma, bullae) for gas embolism
- Inexperience and diving without dive computers or tables

## Pathophysiology

At depth the body absorbs extra nitrogen under pressure (Henry's law). If ascent is too fast, the gas comes out of solution as bubbles in tissues and veins, causing mechanical damage, blocked vessels, endothelial injury and platelet and complement activation. Venous bubbles are usually filtered by the lungs, but they can cross a patent foramen ovale into the arteries. The [spinal cord](https://durgical.com/en/anatomy/spinal-cord/), especially the thoracic cord, is often affected through its venous drainage. In arterial gas embolism, expanding gas ruptures alveoli (Boyle's law) and air enters the [pulmonary veins](https://durgical.com/en/anatomy/pulmonary-veins/) and travels to the brain.

## Classification

- Decompression sickness type I: joint pain ('the bends'), [skin](https://durgical.com/en/anatomy/skin/) and lymphatic signs
- Decompression sickness type II: neurological, inner ear or cardiopulmonary ('the chokes') involvement
- Arterial gas embolism: sudden brain signs within minutes of surfacing
- Barotrauma: middle ear (most common), inner ear, sinus, dental and pulmonary

## Symptoms and signs

- Deep aching pain in the shoulders, elbows or knees, usually within hours of the dive
- Itching, mottled or marbled skin and swollen areas
- Numbness, tingling, weakness of the legs, urinary retention or back pain (spinal cord)
- Vertigo, ringing in the ears and hearing loss
- Chest pain, cough and shortness of breath
- Unconsciousness, seizures, stroke-like weakness or confusion within minutes of surfacing (gas embolism)
- Ear pain, blood from the ear or nose and sinus pain (barotrauma)

## Red flags

- Loss of consciousness within 10 minutes of surfacing
- Weakness, numbness, bladder dysfunction or back pain after a dive
- Breathing difficulty or chest pain
- Sudden deafness or severe vertigo
- Symptoms worsening during a flight or road trip over mountains

## Diagnosis

**Clinical**
A clinical diagnosis based on the dive profile (depth, time, ascent, number of dives), timing of symptoms and a careful neurological examination. Any symptom after a dive is decompression illness until proven otherwise.

**Tests**
Not needed to start treatment; haematocrit (haemoconcentration), glucose and other tests as for any acutely ill patient.

**Imaging**
[Chest](https://durgical.com/en/anatomy/region/chest/) X-ray to look for pneumothorax before recompression; CT or MRI of the brain and [spine](https://durgical.com/en/anatomy/region/spine/) only if they do not delay transfer to a hyperbaric chamber.

## Differential diagnosis

- Ischaemic or haemorrhagic stroke
- Pneumothorax from another cause
- Musculoskeletal strain from carrying dive gear
- Inner ear barotrauma versus inner ear decompression sickness
- Hypoglycaemia, near-drowning, contaminated breathing gas (carbon monoxide) or marine envenomation

## Goal of treatment

Shrink the bubbles and wash out nitrogen as fast as possible with high-concentration oxygen and recompression, and support breathing and circulation.

## Treatment

**Acute**
Lay the diver flat, basic life support if needed, and the highest possible concentration of oxygen without interruption until arrival at a chamber; isotonic glucose-free intravenous fluids. Evacuation by ground or by aircraft flying low or pressurised to sea level.

**Procedure**
Recompression with hyperbaric oxygen is the definitive treatment and is given even if symptoms improve with oxygen; a chest drain is placed first if there is a pneumothorax.

**Follow-up**
Repeated neurological examination, bladder catheter for urinary retention, fluid balance and observation for recurrence after treatment.

**Conservative**
Barotrauma of the ear and sinuses: stop diving, decongestants and pain relief; persistent hearing loss or vertigo needs specialist assessment.

**Lifestyle**
Fitness-to-dive review after recovery; testing for patent [foramen ovale](https://durgical.com/en/anatomy/foramen-ovale/) in selected divers; safe ascent rates and waiting before flying after diving.

## Drugs for this condition

- [Oxygen](https://durgical.com/en/pharmacology/oxygen/)

## Complications

- Permanent paraplegia or incomplete spinal cord injury
- Stroke-like brain injury and death from gas embolism
- Hearing loss and chronic vertigo
- Bone necrosis (dysbaric osteonecrosis) of the hip and shoulder in repeated divers
- Pneumothorax and mediastinal emphysema

## Prognosis

Joint and skin forms usually resolve completely with recompression. Neurological decompression sickness and gas embolism have good outcomes when recompression is quick, but delay increases the risk of permanent deficits; artisanal divers with repeated untreated episodes often remain disabled.

## Prevention

- Follow dive tables or computers, ascend slowly and make safety stops
- Avoid flying for 12 to 24 hours or more after diving, depending on the dives
- Never hold the breath while ascending with compressed air
- Training, medical screening and safety programmes for artisanal divers

## Test yourself

Think of the answer, then tap the question to see it.

## Which gas law explains why nitrogen forms bubbles during a fast ascent?

Henry's law: more gas dissolves under higher pressure, and when pressure falls quickly the gas comes out of solution as bubbles.

## What is the definitive treatment for decompression sickness?

Recompression with hyperbaric oxygen; high-concentration oxygen is given in the meantime and does not replace the chamber.

## A diver loses consciousness within minutes of surfacing. What is the most likely diagnosis?

Arterial gas embolism from lung overexpansion, with air reaching the brain through the pulmonary veins.

## Which cardiac defect increases the risk of neurological decompression sickness?

A patent foramen ovale, which lets venous bubbles cross into the arterial circulation.

## What should be checked on the chest X-ray before recompression?

A pneumothorax, which must be drained first because it would expand during decompression.

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## Related conditions

- [Pneumothorax](https://durgical.com/en/conditions/pneumothorax/)
- [Ischaemic stroke](https://durgical.com/en/conditions/ischaemic-stroke/)
- [Spinal cord injury](https://durgical.com/en/conditions/spinal-cord-injury/)
- [Pulmonary embolism](https://durgical.com/en/conditions/pulmonary-embolism/)
- [Fat embolism syndrome](https://durgical.com/en/conditions/fat-embolism-syndrome/)
- [Avascular necrosis of the femoral head](https://durgical.com/en/conditions/avascular-necrosis-of-the-femoral-head/)
- [Drowning](https://durgical.com/en/conditions/drowning/)
- [Carbon monoxide poisoning](https://durgical.com/en/conditions/carbon-monoxide-poisoning/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Scuba Diving: Decompression Illness and Other Dive-Related Injuries](https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/scuba-diving-decompression-illness-and-other-dive-related-injuries.html) (CDC Yellow Book, Centers for Disease Control and Prevention, 2026).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/decompression-sickness-and-diving-injuries/