(See also Overview of Diving Injuries Overview of Diving Injuries More than 1000 diving-related injuries occur annually in the US; > 10% are fatal. Similar injuries can befall workers in tunnels or caissons (watertight retaining structures used for construction)... read more .)
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 Carbon monoxide poisoning Various physiologic (eg, oxygen, nitrogen, carbon dioxide) and nonphysiologic (eg, carbon monoxide) gases can cause symptoms during diving. (See also Overview of Diving Injuries.) Oxygen toxicity... read more , mechanisms include decreasing the half-life of carboxyhemoglobin, reducing ischemia and oxidative stress, 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* 
).
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, 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. 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 Overview of Barotrauma Barotrauma is tissue injury caused by a pressure-related change in body compartment gas volume in air-containing areas. During ascent, gas expansion affects the lungs and gastrointestinal (GI)... read more , including ear and sinus barotrauma Ear and Sinus Barotrauma Barotrauma is tissue injury caused by a pressure-related change in body compartment gas volume. It can affect the ear (causing ear pain, hearing loss, and/or vestibular symptoms) or the sinuses... read more . Myopia can occur after 20-30 hyperbaric treatments that is usually reversible. Rarely, pulmonary barotrauma Pulmonary Barotrauma Barotrauma is tissue injury caused by a pressure-related change in body compartment gas volume. Factors increasing risk of pulmonary barotrauma include certain behaviors (eg, rapid ascent, breath-holding... read more , 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 How To Do Tube and Catheter Thoracostomy Surgical tube thoracostomy is insertion of a surgical tube into the pleural space to drain air or fluid from the chest. Pneumothorax that is recurrent, persistent, traumatic, large, under tension... read more 
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
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
US Navy Diving Manual: Detailed reference guide published by the US Navy detailing diver training and diving operations
