Recompression therapy is administration of 100% oxygen for up to several hours in a sealed chamber pressurized to at least 1.9 (usually 1.9 to 3.0) atmospheres, gradually lowered to atmospheric pressure. In divers, this therapy is used primarily for decompression sickness, arterial gas embolism, carbon monoxide poisoning, and other conditions. 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.
(See also Overview of Diving Injuries.)
The goals of recompression therapy in diving injuries may include all of the following:
Increasing oxygen solubility and delivery
Increasing nitrogen washout
Decreasing carbon monoxide concentration
Decreasing gas bubble size
Reducing tissue ischemia
Anti-inflammatory effect
For carbon monoxide poisoning, mechanisms include decreasing the half-life of carboxyhemoglobin, reducing ischemia and oxidative stress, and possibly improving mitochondrial function.
Hyperbaric oxygen therapy is a term used when the aim is primarily to give high concentrations of oxygen at increased pressure. It is used to treat decompression sickness and arterial gas embolism, and also used for several disorders unrelated to diving (see table Hyperbaric Oxygen Therapy).
Hyperbaric Oxygen Therapy*
Supporting Evidence | Disorders |
|---|---|
Good | Acute retinal artery occlusion or retinal vein occlusion Dysbaric osteonecrosis (avascular bone necrosis) Clostridial and nonclostridial necrotizing fasciitis 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) |
Fair | 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 United States, 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 late 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, they have some disadvantages when used for critically ill patients, such as limited access to patients who may require intervention while in the chamber.
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. For treatment of decompression illness, chamber pressure is usually initially maintained between 2.5 and 3.0 ATA.
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 U.S. 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 in patients receiving multiple (> 20) hyperbaric treatments for chronic conditions and is usually reversible after cessation of hyperbaric oxygen, typically at a rate similar to its onset. 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 unless the pneumothorax is small and the patient is being treated in a multiplace chamber with staff and equipment required to treat tension pneumothorax immediately available.
Relative contraindications include
Obstructive lung disorders
Upper respiratory or sinus infections
Severe heart failure
Recent ear surgery or injury
Claustrophobia
Recent chest surgery
Pregnancy is generally considered a contraindication for the treatment of chronic conditions with multiple hyperbaric treatments. (See table Hyperbaric Oxygen Therapy.) However, the risk to the fetus of a single hyperbaric treatment for an acute condition such as carbon monoxide poisoning is felt to be less than the risk of leaving the condition untreated.
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 generally require tube thoracostomy before recompression therapy.
More Information
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
Divers Alert Network: 24-hour emergency hotline, 919-684-9111
Duke Dive Medicine: Physician-to-physician consultation, 919-684-8111
Undersea and Hyperbaric Medical Society: Scientific and medical information pertaining to undersea and hyperbaric medicine through its bimonthly, peer-reviewed journal, Undersea and Hyperbaric Medicine, and other resources
U.S. Navy Diving Manual: Detailed reference guide published by the US Navy detailing diver training and diving operations
