Hyperbaric Chamber: What is it? Medical Uses, Contraindications, Therapeutic Principles and History

It is the medical use of 100% pure oxygen in a pressurized place.

Hyperbaric therapy is a medical treatment in which an ambient pressure greater than the atmospheric pressure of sea level is a necessary component.

Treatment includes hyperbaric oxygen therapy (HBOT), medical use of oxygen at an ambient pressure higher than atmospheric pressure, and therapeutic recompression for decompression sickness .

Its goal is to reduce the detrimental effects of systemic gas bubbles by physically reducing their size and providing better conditions.

Therapeutic recompression is generally also provided in a hyperbaric chamber. It is the definitive treatment for decompression sickness and can also be used to treat arterial air embolism caused by ascending pulmonary barotrauma.

In emergency situations, divers can sometimes be treated by in-water recompression if a chamber is not available and adequate scuba equipment is available to reasonably secure the airway.

Over the years, several hyperbaric treatment programs have been published for therapeutic recompression and hyperbaric oxygen therapy for other conditions.


Hyperbaric medicine includes hyperbaric oxygen treatment, which is the medical use of oxygen at a pressure greater than atmospheric to increase the availability of oxygen in the body.

And therapeutic recompression, which involves increasing the ambient pressure in a person, usually a diver, to treat decompression sickness or an air embolism by removing bubbles that have formed within the body.

Medical uses

In the United States, the Underwater and Hyperbaric Medical Society, known as UHMS, lists approvals for reimbursement for certain diagnoses at hospitals and clinics.

Evidence is insufficient to support its use in autism, cancer, diabetes, HIV / AIDS, Alzheimer’s disease, asthma, Bell’s palsy, cerebral palsy, depression, heart disease, migraines, multiple sclerosis, Parkinson’s disease, spinal injury spinal cord, sports injuries or running.

A Cochrane review published in 2016 has raised questions about the ethical basis for future clinical trials of hyperbaric oxygen therapy, in light of the increased risk of damage to the eardrum in children with autism spectrum disorders.

Despite the lack of evidence, in 2015, the number of people using this therapy has continued to rise.

Hearing problems

There is limited evidence that hyperbaric oxygen therapy improves hearing in patients with sudden sensorineural hearing loss presenting within two weeks of hearing loss.

There is some evidence that hyperbaric oxygen therapy might improve tinnitus that occurs in the same time frame.

Chronic ulcers

Hyperbaric oxygen therapy in diabetic foot ulcers increased the rate of early ulcer healing, but did not appear to provide any benefit in wound healing in long-term follow-up.

In particular, there was no difference in the rate of major amputation. For venous, arterial and pressure ulcers, there was no evidence that hyperbaric oxygen therapy provides a long-term improvement over standard treatment.

Radiation injury

There is some evidence that hyperbaric oxygen therapy is effective for late radiation injury to bone tissues and soft tissues of the head and neck.

Some people with radiation injuries to the head, neck, or intestine show an improvement in quality of life. Importantly, no such effect has been found in neurological tissues.

The use of hyperbaric oxygen therapy may be justified for selected patients and tissues, but more research is required to establish the best people to treat and the timing of any hyperbaric oxygen therapy.


As of 2012, there is insufficient evidence to support the use of hyperbaric oxygen therapy to treat people who have traumatic brain injuries.

In stroke, hyperbaric oxygen therapy shows no benefit. Hyperbaric oxygen therapy in multiple sclerosis has not shown benefits and its routine use is not recommended.

A 2007 review of hyperbaric oxygen therapy in cerebral palsy found no difference compared to the control group.

Neuropsychological tests also showed no difference between hyperbaric oxygen therapy and room air, and according to the caregiver’s report, those who received room air had significantly better mobility and social functioning.

Children receiving hyperbaric oxygen therapy were reported to experience seizures and the need for tympanostomy tubes to equalize ear pressure, although the incidence was unclear.


In alternative medicine, hyperbaric medicine has been promoted as a treatment for cancer.

A 2012 review article in the journal Directed Oncology reports that “there is no evidence to suggest that hyperbaric oxygen does not act as a tumor growth stimulator or a recurrence enhancer.

On the other hand, there is evidence that implies that hyperbaric oxygen could have tumor-inhibiting effects in certain subtypes of cancer and, therefore, we strongly believe that we need to expand our knowledge about the effect and mechanisms behind tumor oxygenation.

The 2011 study by the American Cancer Society reported no evidence that it is effective for this purpose.


Low-quality evidence suggests that hyperbaric oxygen therapy can reduce pain associated with an acute migraine in some cases.

It is not known which people would benefit from this treatment, and there is no evidence that hyperbaric medicine can prevent future migraines.

More research is needed to confirm the effectiveness of hyperbaric oxygen therapy for treating migraines.


The toxicology of the treatment has recently been reviewed by Ustundag et al. and Christian R. Mortensen discusses their risk management, as most hyperbaric facilities are run by anesthesiology departments and some of their patients are seriously ill.

The only absolute contraindication to hyperbaric oxygen therapy is untreated pneumothorax.

The reason is the concern that it may progress to pneumothorax tension, especially during the decompression phase of therapy, although oxygen-based table treatment may prevent such progression.

The chronic obstructive pulmonary disease patient with a large blister represents a relative contraindication for similar reasons.

In addition, treatment can raise the issue of Occupational Health and Safety (OHS), which has been encountered by the therapist.

The following are relative contraindications, which means that specialist doctors should take special care before starting hyperbaric oxygen treatments:

Heart disease. Chronic obstructive pulmonary disease with air trapping: can lead to pneumothorax during treatment.

Upper respiratory infections : These conditions can make it difficult for the patient to equalize their ears or sinuses, which can result in what is called ear compression or sinusitis.

High Fevers: In most cases, the fever should be reduced before hyperbaric oxygen treatment begins. Fevers can predispose to seizures.

Emphysema with CO2 retention : This condition can lead to pneumothorax during hyperbaric oxygen treatment due to rupture of an emphysematous bulla. This risk can be assessed by X-ray.

History of thoracic (chest) surgery – This is rarely a problem and is generally not considered a contraindication.

However, there are concerns that air may be trapped in injuries created by surgical scarring. These conditions should be evaluated before considering hyperbaric oxygen therapy.

Malignant disease : Cancers grow in environments rich in blood, but can be suppressed by high oxygen levels.

Hyperbaric oxygen treatment in individuals who have cancer presents a problem, as hyperbaric oxygen increases blood flow through angiogenesis and also raises oxygen levels.

Taking an anti-angiogenic supplement can provide a solution.

A study by Feldemier, et al. and a recent study from the National Institutes of Health, funded with stem cells by Thom, et al., indicates that hyperbaric oxygen is indeed beneficial in the production of stem / progenitor cells and that the malignant process is not accelerated.

Middle ear barotrauma is always a consideration in treating children and adults in a hyperbaric environment due to the need to equalize pressure in the ears.

Pregnancy is not a relative contraindication to hyperbaric oxygen treatments, although it may be for underwater diving.

In cases where a pregnant woman has carbon monoxide poisoning, there is evidence that lower pressure hyperbaric oxygen therapy (2.0 ATA) treatments are not harmful to the fetus.

And that the risk involved is outweighed by the increased risk of the untreated effects of carbon monoxide on the fetus (neurological abnormalities or death).

In pregnant patients, hyperbaric oxygen therapy has been shown to be safe for the fetus when administered at appropriate levels and “doses” (durations).

In fact, pregnancy lowers the threshold for hyperbaric oxygen treatment in patients exposed to carbon monoxide. This is due to the high affinity of fetal hemoglobin for carbon monoxide.

Therapeutic principles

The therapeutic consequences of hyperbaric oxygen therapy and recompression result from multiple effects.

The general pressure increase is of therapeutic value in the treatment of decompression sickness and air embolism, as it provides a physical means of reducing the volume of inert gas bubbles within the body.

Exposure to this increased pressure is sustained for a period long enough to ensure that most of the gas in the bubble dissolves back into the tissues, is removed by perfusion, and is eliminated in the lungs.

The improved concentration gradient for inert gas removal (oxygen window) by using a high partial pressure of oxygen increases the inert gas removal rate in the treatment of decompression sickness.

For many other conditions, the therapeutic principle of hyperbaric oxygen therapy lies in its ability to dramatically increase the partial pressure of oxygen in the body’s tissues.

The partial pressures of oxygen that can be achieved with hyperbaric oxygen therapy are much higher than those that can be achieved by breathing pure oxygen under normobaric conditions (that is, at normal atmospheric pressure).

This effect is achieved by an increase in the oxygen carrying capacity of the blood.

At normal atmospheric pressure, oxygen transport is limited by the binding capacity of hemoglobin in red blood cells, and blood plasma carries very little oxygen.

Because the hemoglobin in red blood cells is nearly saturated with oxygen at atmospheric pressure, this transport route can no longer be exploited.

However, plasma oxygen transport is significantly increased with hyperbaric oxygen therapy due to the increased solubility of oxygen as pressure increases.

One study suggests that exposure to hyperbaric oxygen (hyperbaric oxygen therapy) could also mobilize bone marrow stem / progenitor cells by a nitric oxide-dependent mechanism.

Hyperbaric chambers


The traditional type of hyperbaric chamber used for therapeutic recompression and hyperbaric oxygen therapy is a rigid pressure vessel with a shell.

Such chambers can be run at absolute pressures, typically around 6 bar (87 psi), 600,000 Pa or more in special cases.

Navies, professional dive organizations, hospitals, and dedicated recompression facilities often operate them.

They range in size from semi-portable single-patient units to room-sized units that can treat eight or more patients.

Larger units can be rated for lower pressures if they are not primarily designed for the treatment of diving injuries.

A rigid camera can consist of:

  • A pressure vessel with acrylic viewing ports (windows).
  • One or more human entry hatches – Small, circular or wheeled hatches for patients on stretchers.
  • The entry lock that allows people to enter: a separate chamber with two hatches, one to the outside and one to the main chamber, which can be independently pressurized to allow patients to enter or exit the main chamber while it is still pressurized.
  • A low volume medical or service airbag for medicines, instruments and food. Transparent ports or closed-circuit television that allow technicians and medical personnel outside the chamber to monitor the patient inside the chamber.
  • An intercom system that allows two-way communication. An optional carbon dioxide scrubber, which consists of a fan that passes the gas into the chamber through a soda lime container.
  • A control panel outside the chamber to open and close the valves that control the flow of air to and from the chamber, and regulate oxygen to the hoods or masks. An overpressure relief valve.
  • A built-in breathing system (bibs) to supply and extract the treatment gas. A fire extinguishing system.

Flexible single-seater cameras are available ranging from flexible aramid fiber reinforced collapsible cameras that can be disassembled for transport by truck or sport utility vehicle.

With a maximum working pressure of 2 bar above room temperature complete with built-in breathing system that allows oxygen for full treatment schedules to air-inflated “soft” portable chambers.

They can operate at a pressure between 0.3 and 0.5 bar (4.4 and 7.3 psi) above atmospheric pressure without supplemental oxygen and longitudinal zip closure.

Oxygen supply

In the larger multiplace chambers, patients inside the chamber breathe through “oxygen hoods” (soft, flexible, transparent plastic hoods with a closure around the neck similar to a spacesuit helmet).

Or tight-fitting oxygen masks that deliver pure oxygen and can be designed to draw exhaled gas directly from the chamber.

During treatment, patients breathe 100% oxygen most of the time to maximize the effectiveness of their treatment, but have periodic ‘air breaks’ during which they breathe chamber air (21% oxygen) to reduce risk oxygen toxicity.

Exhaled treatment gas must be removed from the chamber to avoid oxygen build-up, which could present a fire hazard.

Attendees can also breathe oxygen a few times to reduce the risk of decompression sickness when they leave the chamber.

The pressure inside the chamber is increased by opening valves that allow high pressure air to enter from the storage cylinders, which are filled with an air compressor.

The oxygen content of the chamber air is kept between 19% and 23% to control the risk of fire (maximum 25% for the US Navy).

If the chamber does not have a cleaning system to remove carbon dioxide from the chamber gas, the chamber must be isobarically vented to keep the CO2 within acceptable limits.

A soft chamber can be pressurized directly from a compressor or from storage cylinders.

The smaller ‘single-seat’ chambers can only accommodate the patient and no medical personnel can enter. The chamber can be pressurized with pure oxygen or compressed air.

If pure oxygen is used, no mask or helmet is needed to breathe oxygen, but the cost of using pure oxygen is much higher than that of using compressed air. If compressed air is used, then an oxygen mask or hood is needed as in a multiplace chamber.

Most single-seat cameras can be equipped with an on-demand breathing system for air breaks.

In low pressure soft chambers, treatment programs may not require air breaks as the risk of oxygen toxicity is low due to the lower oxygen partial pressures used (generally 1.3 ATA) and the short duration treatment.

For alert, cooperative patients, the air breaks provided by the mask are more effective than changing the gas in the chamber because they provide a faster gas change and a more reliable gas composition during both rest and treatment periods.


Initially, hyperbaric oxygen therapy was developed as a treatment for diving disorders that involve gas bubbles in the tissues, such as decompression sickness and air embolism. It is still considered the definitive treatment for these conditions.

The chamber treats decompression sickness and gas embolism by increasing pressure, reducing the size of gas bubbles, and improving blood transport to downstream tissues.

After the removal of bubbles, the pressure is gradually reduced to atmospheric levels. Hyperbaric chambers are also used for animals, especially racehorses, where a recovery is worth a lot to their owners.

It is also used to treat dogs and cats in pre and postoperative treatment to strengthen their systems before surgery and then accelerate healing after surgery.


Emergency hyperbaric oxygen therapy for decompression sickness follows the treatment schedules outlined in the treatment charts.

Most cases employ a recompression to 2.8 bars (41 psi) absolute, the equivalent of 18 meters (60 feet) of water, for 4.5 to 5.5 hours with the victim breathing pure oxygen, but taking air breaks every 20 minutes to reduce oxygen toxicity.

For extremely severe cases resulting from very deep dives, treatment may require a chamber capable of a maximum pressure of 8 bar (120 psi), the equivalent of 70 meters (230 feet) of water, and the ability to deliver heliox as a gas. breathing.

The United States Navy Treatment Charts are used in Canada and the United States to determine the duration, pressure, and breathing gas of therapy.

The most frequently used tables are Table 5 and Table 6. In the UK, Royal Navy tables 62 and 67 are used.

The Underwater Hyperbaric Medical Society (UHMS) publishes a report that compiles the latest research results and contains information on the recommended duration and pressure of longer-term conditions.

Home and outpatient treatment

There are various sizes of portable chambers, which are used for home treatment. These are generally called “mild personal hyperbaric chambers,” which are a reference to the lower pressure (compared to hard chambers) of the soft-sided chambers.

In the US, these “mild personal hyperbaric chambers” are classified by the Food and Drug Administration as CLASS II medical devices and require a prescription to purchase one or receive treatments.

The most common option (but not approved by the Food and Drug Administration) that some patients choose is to purchase an oxygen concentrator that generally delivers 85-96% oxygen as a breathing gas.

Oxygen is never fed directly into the soft chambers, but is introduced through a line and a mask directly to the patient.

Oxygen concentrators approved by the Food and Drug Administration for human consumption in confined areas used for hyperbaric oxygen therapy are regularly monitored for purity (+/- 1%) and flow (10 to 15 liters per minute of outlet pressure).

An audible alarm will sound if the purity ever falls below 80%. Hyperbaric personal chambers use 120-volt or 220-volt outlets.

Possible complications and concerns

There are risks associated with hyperbaric oxygen therapy, similar to some diving disorders.

Pressure changes can cause a “squeeze” or barotrauma in the tissues that surround trapped air within the body, such as the lungs, behind the eardrum, within the sinuses, or trapped under dental fillings.

Breathing oxygen at high pressure can cause oxygen toxicity. Temporarily blurred vision can be caused by inflammation of the lens, which usually resolves in two to four weeks.

There are reports that cataract can progress after hyperbaric oxygen therapy.

Effects of pressure

Patients inside the chamber may notice discomfort within their ears when a pressure difference develops between the middle ear and the chamber atmosphere.

This can be relieved by cleaning the ear using the Valsalva maneuver or other techniques.

The continuous increase in unmatched pressure can cause the eardrums to rupture, resulting in severe pain. As the pressure in the chamber increases, the air can heat up.

To reduce the pressure, a valve is opened to allow air to escape from the chamber. As the pressure drops, the patient’s ears may “screech” as the pressure inside the ear equalizes with the chamber. The temperature in the chamber will drop.

The speed of pressurization and depressurization can be adjusted to the needs of each patient.


Hyperbaric air

Junod built a chamber in France in 1834 to treat pulmonary conditions at pressures between 2 and 4 absolute atmospheres.

During the next century, “pneumatic centers” were established in Europe and the US that used hyperbaric air to treat various conditions.

Orval J Cunningham, a professor of anesthesia at the University of Kansas in the early 1900s, observed that people with circulatory disorders performed better at sea level than at altitude, and this formed the basis for his use of hyperbaric air.

In 1918 he successfully treated Spanish flu patients with hyperbaric air. In 1930, the American Medical Association forced him to stop hyperbaric treatment, as he did not provide acceptable evidence that the treatments were effective.

Hyperbaric oxygen

The English scientist Joseph Priestley discovered oxygen in 1775.

Shortly after its discovery, there were reports of toxic effects of hyperbaric oxygen on the central nervous system and lungs, delaying therapeutic applications until 1937, when Behnke and Shaw first used it in the treatment of decompression sickness.

In 1955 and 1956, Churchill-Davidson, in the United Kingdom, used hyperbaric oxygen to improve the radiosensitivity of tumors, while nl, at the University of Amsterdam, used it successfully in cardiac surgery.

In 1961 Willem Hendrik Brummelkamp (nl) et al. published on the use of hyperbaric oxygen in the treatment of clostridial gas gangrene.

In 1962, Smith and Sharp reported on the successful treatment of carbon monoxide poisoning with hyperbaric oxygen.

The Underwater Medical Society (now the Underwater and Hyperbaric Medical Society) formed a Hyperbaric Oxygenation Committee that has been recognized as the authority on indications for the treatment of hyperbaric oxygen.