Hyperbaric oxygenation

Hyperbaric oxygenation is the administration of 100% O2 for several hours in a sealed chamber with a pressure greater than 1 atm, which is gradually reduced to atmospheric pressure. In divers, this treatment is administered primarily for decompression sickness and arterial gas embolism. The sooner the therapy is started, the better the result. Untreated pneumothorax must be drained before or during recompression.

The goals of recompression therapy are to increase O2 solubility and delivery, accelerate N washout, reduce gas bubble size, and in rare cases associated with carbon monoxide poisoning, decrease CO2 half-life and reduce tissue ischemia. Hyperbaric oxygenation (HBO) is also used for other medical indications unrelated to diving.

Hyperbaric oxygenation*

Supporting data	Violations
Sufficient quantity	Arterial gas embolism CO poisoning (severe) Clostridial infection Decompression sickness Osteoradionecrosis Poorly healing wounds (including skin grafts)
A small amount	Anemia (severe) with hemorrhagic shock Burns Intracranial abscess in actinomycosis Necrotizing fasciitis Radiation damage to soft tissues Refractory osteomyelitis Crush syndrome with compartment syndrome Wound healing in ischemic limbs
Few or none	Dementia Multiple sclerosis

Hyperbaric oxygenation is the mainstay of treatment for diving-related decompression injury and arterial gas embolism. It is also being tried in many other conditions. The effectiveness of hyperbaric oxygenation has been most clearly demonstrated for a small number of conditions. Relative contraindications include chronic pulmonary dysfunction, sinus disease, seizure disorders, and claustrophobia. Pregnancy is not a contraindication.

Recompression is relatively well tolerated by patients and should be started immediately, even though there is little chance that it will speed recovery. Recompression may help even if started much later, after 48 hours after surfacing.

HBO chambers are available as single- and multi-person chambers with space for several patients on stretchers or in a chair, as well as for an accompanying medical worker. Although the costs of single-person HBO chambers are significantly lower, they do not provide access to the patient during treatment. Their use for patients in critical conditions who may require additional interventions is not recommended.

Most divers, paramedics, rescuers and police officers in popular diving areas should have information about the location of the nearest SCUBA recompression chamber, the shortest route to it and a contact phone number for emergency consultation.

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Recompression protocols

The pressure and duration of treatment ("immersion") are usually determined by the recompression facility. Treatment is given once or twice daily for 45-300 min until symptoms subside; "air breaks" are given for 5-10 min to reduce the risk of O2 toxicity. Chamber pressure is usually maintained between 2.5 and 3.0 atm, but patients with life-threatening neurological symptoms resulting from gas embolism are often treated with 6 atm to quickly compress gas bubbles in the brain.

Although recompression therapy is usually performed using 100% O2 or compressed air, special gas mixtures (e.g. helium/O2 or nitrogen/O2 in non-atmospheric proportions) may be used and are particularly indicated if the diver has been diving with an unusual gas mixture or the depth/duration of the dive has been extraordinary.

Patients with residual neurological deficit are treated with repeated intermittent hyperbaric oxygen therapy; a course of several days or weeks may be required to achieve maximum recovery.

Complications and contraindications of hyperbaric oxygenation

Recompression therapy may cause problems similar to those seen with barotrauma, including reversible myopia, ear barotrauma, and sinus barotrauma. Rarely, pulmonary barotrauma, pulmonary O2 intoxication, hypoglycemia, or seizures may occur. The risk of complications associated with barotrauma or CNS O2 injury is increased in patients with a history of seizures, pneumothorax, or thoracic surgery. Sedatives and opioid analgesics may obscure symptoms and cause respiratory failure and should be avoided or used only in minimal doses.

Relative contraindications include COPD, upper respiratory tract or sinus infections, recent ear surgery or injury, fever, and claustrophobia.

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