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Recompression Therapy

(Hyperbaric O2 Therapy)

By Alfred A. Bove, MD, PhD

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Patient Education

Recompression therapy is administration of 100% O2 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 48 hours 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 O2 solubility and delivery

  • Increasing N2 washout

  • Decreasing CO 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 O2 therapy is also used for several disorders unrelated to diving (see Table: Hyperbaric O 2 Therapy*).

Hyperbaric O 2 Therapy*

Supporting Evidence



Arterial gas embolism

Clostridial infection

Decompression sickness


Poorly healing skin grafts


Anemia (severe) with hemorrhagic shock


Carbon monoxide poisoning (severe)

Intracranial abscess with actinomycosis

Necrotizing fasciitis

Radiation soft-tissue injury

Refractory osteomyelitis

Traumatic crush injury and compartment syndrome

Wound healing in ischemic limbs

Acute retinal artery or vein occlusion

*Hyperbaric O2therapy (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 include chronic lung disorders, sinus problems, seizure disorders, and claustrophobia. Pregnancy is not a contraindication. 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 ).

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 48 h after surfacing. However, success is usually low if started > 48 h after symptom onset, except for exposure to altitude (eg, flying) after diving, in which case therapy could be successful even a few days after altitude exposure.

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 h/day. The Undersea and Hyperbaric Medical Society ( ) is another invaluable source of general information about recompression.

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/day for 45 to 300 min until symptoms abate; 5- to 10-min air breaks are added to reduce risk of O2 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% O2 or compressed air, special gas mixtures (eg, helium/O2 or N2/O2 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. O2toxicity can cause reversible myopia. Rarely, pulmonary barotrauma, pulmonary O2 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

  • Fever

  • Claustrophobia

  • Seizure disorder

  • Chest surgery

Key Points

  • Arrange for indicated recompression therapy to be done as soon as possible.

  • Do not exclude recompression therapy based on the amount of time elapsed since surfacing; however, except for altitude exposure after diving, success rate for recompression therapy is low when started > 48 h after symptom onset.

  • 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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