Hyperbaric medicine
Hyperbaric medicine is medical treatment in which an increase in barometric pressure of typically air or oxygen is used. The immediate effects include reducing the size of gas emboli and raising the partial pressures of the gases present. Initial uses were in decompression sickness, and it also effective in certain cases of gas gangrene and carbon monoxide poisoning. There are risks associated with hyperbaric therapy, including barotrauma, and, if pure oxygen is used, a fire hazard.
Hyperbaric oxygen therapy is the medical use of greater than 99% oxygen at an ambient pressure higher than atmospheric pressure, and therapeutic recompression. The equipment required consists of a pressure vessel for human occupancy, which may be of rigid or flexible construction, and a means of a controlled atmosphere supply. Treatment gas may be the ambient chamber gas, or delivered via a built-in breathing system. Operation is performed to a predetermined schedule by personnel who may adjust the schedule as required.
Hyperbaric air consists of compressed atmospheric air and is used for acute mountain sickness. This is applied by placing the person in a portable hyperbaric air chamber and inflating that chamber up to using a foot-operated or electric air pump.
Chambers used in the US made for hyperbaric medicine fall under the jurisdiction of the federal Food and Drug Administration. The FDA requires hyperbaric chambers to comply with the American Society of Mechanical Engineers PVHO Codes and the National Fire Protection Association Standard 99, Health Care Facilities Code. Similar conditions apply in most other countries.
Other uses include arterial gas embolism caused by pulmonary barotrauma of ascent. In emergencies divers may sometimes be treated by in-water recompression if suitable diving equipment is available.
Scope
Hyperbaric medicine includes hyperbaric oxygen treatment, which is the medical use of oxygen at greater than atmospheric pressure to increase the availability of oxygen in the body; and therapeutic recompression, which involves increasing the ambient pressure on a person, usually a diver, to treat decompression sickness or an air embolism by reducing the volume and more rapidly eliminating bubbles that have formed within the body.Medical uses
The Undersea and Hyperbaric Medical Society lists 15 supported uses as of 2025:- Air or gas embolism;
- Carbon monoxide poisoning including that complicated by cyanide poisoning;
- Clostridal myositis and myonecrosis ;
- Crush injury, compartment syndrome, and other acute traumatic ischemias;
- Decompression sickness;
- Central retinal artery occlusion and enhancement of healing in selected problem wounds due to insufficient arterial blood flow, including the diabetic foot;
- Exceptional blood loss ;
- Intracranial abscess;
- Necrotizing soft tissue infections ;
- Osteomyelitis ;
- Delayed radiation injury ;
- Skin grafts and flaps ;
- Thermal burns ;
- Idiopathic sudden sensorineural hearing loss;
- Avascular necrosis
Mucormycosis, especially rhinocerebral disease in the setting of diabetes mellitus may be supported.
There is insufficient evidence for use in autism, cancer, diabetes, HIV/AIDS, Alzheimer's, asthma, Bell's palsy, cerebral palsy, depression, heart disease, migraines, multiple sclerosis, Parkinson's, spinal cord injury, sports injuries, or stroke. Furthermore, potential side effects pose an unjustified risk in such cases. A 2016 meta-analysis found no evidence of improvements in social abilities or cognitive functioning in autistic individuals treated with HBOT. The paper also noted conducting further trials would be ethically fraught, as HBOT can cause damage to the eardrum. Despite the lack of evidence, in 2015, the number of people utilizing this therapy has continued to rise. There is also insufficient evidence to support its use in acute traumatic or surgical wounds.
Hearing
There is limited evidence for sudden sensorineural hearing loss within two weeks of onset. It might improve tinnitus presenting in the same time frame.Chronic ulcers
HBOT in diabetic foot ulcers increased the rate of early ulcer healing but does not appear to provide any benefit in wound healing at long-term follow-up. In particular, there was no difference in major amputation rate. For venous, arterial and pressure ulcers, no evidence was apparent that HBOT provides a long-term improvement over standard treatment.Radiation injury
There is some evidence that HBOT is effective for late radiation tissue injury of bone and soft tissues of the head and neck. Some people with radiation injuries of the head, neck or bowel show an improvement in quality of life. Importantly, no such effect has been found in neurological tissues. The use of HBOT may be justified to selected patients and tissues, but further research is required to establish the best people to treat and timing of any HBO therapy.Neuro-rehabilitation
As of 2012, there was insufficient evidence to support use in traumatic brain injuries. In acute stroke, HBOT does not show benefit.HBOT in multiple sclerosis has not shown benefit and routine use is not recommended.
A 2007 review in cerebral palsy found no difference compared to the control group. Neuropsychological tests also showed no difference between HBOT and room air and based on caregiver report, those who received room air had significantly better mobility and social functioning. Children experienced seizures and the need for tympanostomy tubes to equalize ear pressure, though the rates was not clear.
Cancer
In alternative medicine, hyperbaric medicine has been promoted for cancer. However, a 2011 study by the American Cancer Society reported no evidence it is effective for this purpose. A 2012 review article found "there is no evidence indicating that HBO neither acts as a stimulator of tumor growth nor as an enhancer of recurrence. On the other hand, there is evidence that implies that HBO might have tumor-inhibitory effects in certain cancer subtypes, and we thus strongly believe that we need to expand our knowledge on the effect and the mechanisms behind tumor oxygenation."Migraines
Low-quality evidence suggests it may reduce pain in an ongoing migraine headache. It is not known which people would benefit from this treatment, and there is no evidence that it prevents future migraines.Side effects
is a limitation on both maximum partial pressure of oxygen, and on length of each treatment.HBOT can accelerate the development of cataracts over multiple repetitive treatments, and can cause temporary relative myopia over the shorter term.
A 2023 review found that negative outcomes were experienced by 24% of patients, but they were not prevented from completing the treatment regimen, and no serious side effects, complications or deaths were reported.
Complications
There are risks associated with HBOT, similar to some diving disorders. Pressure changes can cause a "squeeze" or barotrauma in the tissues surrounding trapped air inside the body, such as the lungs, behind the eardrum, inside paranasal sinuses, or trapped underneath dental fillings. Breathing high-pressure oxygen may cause oxygen toxicity. Temporarily blurred vision can be caused by swelling of the lens, which usually resolves in two to four weeks.There are reports that cataracts may progress following HBOT, and rarely, may develop de novo, but this may be unrecognized and under reported. The cause is not fully explained, but evidence suggests that lifetime exposure of the lens to high partial pressure oxygen may be a major factor. Oxidative damage to lens proteins is thought to be responsible. This may be an end-stage of the relatively well documented myopic shift detected in most hyperbaric patients after a course of multiple treatments.
Ears
People have ear discomfort as a pressure difference develops between their middle ear and the chamber atmosphere. This can be relieved by ear clearing using the Valsalva maneuver or other techniques. Continued increase of pressure without equalizing may cause ear drums to rupture, resulting in severe pain. As the pressure in the chamber increases further, the air may become warm.To reduce the pressure, a valve is opened to allow air out of the chamber. As the pressure falls, the patient's ears may "squeak" as the pressure inside the ear equalizes with the chamber. The temperature in the chamber will fall. The speed of pressurization and de-pressurization can be adjusted to each patient's needs.
Contraindications
The toxicology of the treatment has been reviewed by Ustundag et al. and its risk management is discussed by Christian R. Mortensen, in light of the fact that most hyperbaric facilities are managed by departments of anaesthesiology and some of their patients are critically ill.An absolute contraindication to hyperbaric oxygen therapy is untreated pneumothorax. The reason is concern that it can progress to tension pneumothorax, especially during the decompression phase of therapy, although treatment on oxygen-based tables may avoid that progression. The COPD patient with a large bleb represents a relative contraindication for similar reasons. Also, the treatment may raise the issue of occupational health and safety, for chamber inside attendants, who should not be compressed if they are unable to equalise ears and sinuses.
Extra care may be required in people with:
- Cardiovascular disease
- COPD with air trapping – can lead to pneumothorax during treatment.
- Upper respiratory infections – These conditions can make it difficult for the patient to equalise their ears or sinuses, which can result in what is termed ear or sinus squeeze.
- High fevers – In most cases the fever should be lowered before HBO treatment begins. Fevers may predispose to convulsions.
- Emphysema with CO2 retention – This condition can lead to pneumothorax during HBO treatment due to rupture of an emphysematous bulla during decompression. This risk can be evaluated by x-ray.
- History of thoracic surgery – This is rarely a problem and usually not considered a contraindication. However, there is concern that air may be trapped in lesions that were created by surgical scarring. These conditions need to be evaluated prior to considering HBO therapy.
- Malignant disease: Cancers thrive in blood-rich environments but may be suppressed by high oxygen levels. HBO treatment of individuals who have cancer presents a problem, since HBO both increases blood flow via angiogenesis and also raises oxygen levels. Taking an anti-angiogenic supplement may provide a solution. A study by Feldemier, et al. and NIH funded study on Stem Cells by Thom, et al., indicate that HBO is actually beneficial in producing stem/progenitor cells and the malignant process is not accelerated.
- Middle ear barotrauma may occur in children and adults in a hyperbaric environment because of the necessity to equalise pressure in the ears.