Hyperbaric oxygen therapy, how does it work?

FOCUS- Extreme divers and mountaineers are familiar with this treatment which re-oxygenates the body during an asphyxiation accident. But it can also be used for chronic diseases.

• What is that?

This treatment takes place in a transportable chamber (high mountain and diving) or, in a hospital environment, in a technical room where several patients can be accommodated at the same time. The interior is overpressurized, that is to say that the air pressure is increased there up to 3 times the normal pressure (which is 1 bar). It is not the overpressure of air that makes it possible to treat patients but the overpressure of pure oxygen (O2): ie 100% O2 in the patient’s lungs, far from the 21% contained in our air. We then speak of hyperbaric oxygen therapy (or overpressure) whose acronym is OHB. This founded the hyperbaric medicine which consists in super-oxygenating the tissues to treat them.

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• When is it used?

It is used in emergency during acute asphyxial accidents: decompression from sports or professional diving, acute mountain sickness (AMS), poisoning by carbon monoxide or gas embolisms. These emergencies are in the minority because the indications are very varied: severe bacterial infections, healing disorders due to poor blood circulation, sudden deafness and crushed limbs to save as many cells as possible, radiotherapy sequelae (bone necrosis, cystitis and radiation colitis ), cerebrovascular accident (CVA) and head trauma.

Compression/decompression can especially injure the eardrums, as in diving or in an airplane. It is therefore necessary to balance the tympanic pressures by yawning or swallowing

• How to prepare for it?

The sessions, generally ten in number, are preceded by an information interview. They are daily, often collective. Fasting is not necessary. Acrylic clothing that generates static electricity is prohibited. Oxygen being flammable and explosive, it is forbidden to smoke, to introduce matches or lighters and electronic equipment because of possible sparks. Do not wear make-up, or smear your face because of the oxygen mask, or wear a watch that would not withstand the overpressure.

• What are the risks?

They are rare, usually minor. But convulsions and dental trauma (due to air bubbles) can occur. Compression/decompression can especially injure the eardrums, as in diving or in an airplane. It is therefore necessary to balance the tympanic pressures by yawning or swallowing (saliva, water), or to practice the Valsalva maneuver: a forced expiration with closed mouth and pinched nose causing the opening of the Eustachian tubes.

The key steps

The hyperbaric chamber or chamber is intended for high pressure oxygen therapy. A combination of air compression in the chamber space and delivery of 100% pure oxygen to the patient using a mask is required.


After passing through an entry/exit airlock, the patient is installed, seated or lying down depending on his condition. The oxygen mask is fitted to his face. A nurse can accompany him, especially at the beginning of the sessions if he is very anxious and claustrophobic. Some centers train their staff in hypnotherapy (medical hypnosis) to curb this anxiety but also the pain of the disease.

The session

It generally lasts 1 hour 30 to 2 hours, but can be longer depending on the disease being treated. The session typically takes place in three phases: 15 minutes of compression (for example at 2.5 bars), 60 minutes of oxygenation in a pressure plateau, and 15 minutes of decompression. The patient can read or do crossword puzzles. In case of disturbances, he must notify the staff. The most common is persistent pain in the eardrums despite balancing maneuvers during compression. In this case, the compression is interrupted until the return to normal. It is also necessary to warn the staff in the event of an oxygen leak at the level of the mask, so that they can readjust it quickly.


The therapeutic effects of hyperbaric oxygen therapy depend on patient compliance. There are no problems away from the session. If they should appear, these occur especially during the sessions.


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