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Recompression Therapy

(Hyperbaric Oxygen Therapy)


Richard E. Moon

, MD, Duke University Medical Center

Last full review/revision Jul 2019| Content last modified Jul 2019
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Recompression therapy is administration of 100% oxygen for several hours in a sealed chamber pressurized to > 1 atmosphere, gradually lowered to atmospheric pressure. In divers, this therapy is used primarily for decompression sickness and arterial gas embolism. A shorter time to start of therapy is associated with a better patient outcome, but therapy should be started anytime within a few days of surfacing. Despite therapy, severe injury predicts a poor outcome. Untreated pneumothorax requires chest tube placement before or at the start of recompression therapy.

The goals of recompression therapy in diving injuries include all of the following:

  • Increasing oxygen solubility and delivery

  • Increasing nitrogen washout

  • Decreasing carbon monoxide concentration

  • Decreasing gas bubble size

  • Reducing tissue ischemia

For carbon monoxide poisoning, mechanisms include decreasing the half-life of carboxyhemoglobin, reducing ischemia, and possibly improving mitochondrial function.

Hyperbaric oxygen therapy is also used for several disorders unrelated to diving (see table Hyperbaric Oxygen Therapy).


Hyperbaric Oxygen Therapy*

Supporting Evidence



Osteoradionecrosis or soft tissue radiation necrosis

Poorly healing skin grafts, compromised flaps

Refractory osteomyelitis

Traumatic crush injury

Ischemic limbs (eg, secondary to diabetic vascular disease)


Anemia (severe) with organ compromise

* Hyperbaric oxygen therapy (HBO) is the mainstay of treatment for diving-related decompression injury and arterial gas embolism. It is also tried for other disorders, but its efficacy is more strongly established for some conditions than others. Relative contraindications for HBO include chronic lung disorders, sinus problems, seizure disorders, and claustrophobia. Pregnancy is not a contraindication to treatment for an acute condition. In the US, HBO chambers can be located by contacting the Divers Alert Network at 919-684-9111 for emergencies and 919-684-2948 for other information Additional information regarding HBO therapy is in Hyperbaric Oxygen Therapy Indications 14th Edition, Undersea & Hyperbaric Medical Society, 2019 (ISBN: 978-1-947239-16-6).

Because recompression is relatively well tolerated, it should be started if there is any likelihood that it would promote recovery; recompression may help even if started up to several days after surfacing. However, success is lower if started > 48 hours after symptom onset.

Recompression chambers are either multiplace, with space for one or more patients on a gurney and for a medical attendant, or monoplace, with space for only one patient. Although monoplace chambers are less expensive, because patients cannot be accessed during recompression, their use for critically ill patients, who may require intervention, can be risky.

Information regarding the location of the nearest recompression chamber, the most rapid means of reaching it, and the most appropriate source to consult by telephone should be known by most divers, medical staff members, and rescue and police personnel in popular diving areas.

Such information is also available from the Divers Alert Network (919-684-9111; 24 hours a day. The Undersea and Hyperbaric Medical Society ( is another invaluable source of general information about recompression. Physician-to-physician consultation can be obtained through Duke Dive Medicine (919-684-8111).

Recompression protocols

Pressure and duration of treatment are usually decided by a hyperbaric medicine specialist at the recompression facility. Treatments are given once or twice a day for 45 to 300 minutes until symptoms abate; 5- to 10-minute air breaks are added to reduce risk of oxygen toxicity. Chamber pressure is usually maintained between 2.5 and 3.0 atmospheres (atm), but patients with life-threatening neurologic symptoms due to gas embolism may begin with an excursion to 6 atm to rapidly compress cerebral gas bubbles.

Although recompression therapy is usually done with 100% oxygen or compressed air, special gas mixtures (eg, helium/oxygen or nitrogen/oxygen in nonatmospheric proportions) may be indicated if the diver used an unusual gas mixture or if depth or duration of the dive was extraordinary. Specific protocol tables for treatment are included in the US Navy Diving Manual.

Patients with residual neurologic deficits should be given repetitive, intermittent hyperbaric treatments and may require several days to reach maximum improvement.

Complications of recompression therapy

Recompression therapy can cause problems similar to those that occur with barotrauma, including ear and sinus barotrauma. Myopia can occur after 20-30 hyperbaric treatments that is usually reversible. Rarely, pulmonary barotrauma, pulmonary oxygen toxicity, hypoglycemia, or seizures result. Sedatives and opioids may obscure symptoms and cause respiratory insufficiency; they should be avoided or used only in the lowest effective doses.

Contraindications to recompression therapy

Patients with pneumothorax require tube thoracostomy before recompression therapy.

Relative contraindications include

  • Obstructive lung disorders

  • Upper respiratory or sinus infections

  • Severe heart failure

  • Recent ear surgery or injury

  • Claustrophobia

  • Recent chest surgery

Key Points

  • Arrange for indicated recompression therapy as soon as possible.

  • Although delays until treatment reduce the success rates, do not exclude recompression therapy based on the amount of time elapsed since surfacing

  • If an unstable patient needs recompression therapy, use a multiplace chamber if possible.

  • Patients with pneumothorax require tube thoracostomy before recompression therapy.

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