Hyperbaric oxygen therapy

Hyperbaric oxygen treatment (HBOT) is a 100% oxygen inhalation treatment inside a hyperbaric chamber. The patient is seated or lying in a hyperbaric chamber which is compressed to an overpressure of 2 bars. Oxygen is breathed through a mask, hood or tracheostomy tube. Depending on the disease, treatment lasts 90 to 300 minutes or more. It may be necessary to repeat the treatment several times a day.(more)

Hyperbaric oxygen therapy consists of inhaling pure oxygen in an environment that has an ambient pressure higher than normal atmospheric pressure. This requires a hyperbaric chamber. The hyperbaric chamber is compressed with air for safety and economic reasons. The physical laws, and in particular that of Dalton make the pressure in the mask or any other breathing system the same as in the hyperbaric chamber. We could say that a patient who breathes 100% oxygen under an overpressure of 2.4 bars in fact breathes 240% oxygen. Outside of a hyperbaric chamber oxygen inhalation is at most 100%.

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Patients can be treated sitting or lying down, depending on their state of health or the number of patients present. The taking of pure medical oxygen (Carbagas) is done either through a facial mask, a transparent hood, a closed and tight respiratory system which is glued directly around the tracheostoma or through a tube in intubated patients. The duration of oxygen respiration is always 2 times 45 minutes except for diving accidents where it generally lasts 5 hours.

Bubble reduction

The effect of the Boyle’s law (p1xv1 = p2xv2) can be seen in many aspects of HBO. This can be useful for embolic phenomena such as decompression sickness (DCS) or arterial gas embolism (AGE). As the pressure increases, the volume of the bladder decreases. This is also important during decompression of the chamber. When a patient holds their breath, the volume of gas trapped in the lungs increases and can lead to pneumothorax.

Temperature change

Charles’ law ([p1xv1] / T1 = [p2xv2] / T2) explains the increase in temperature during compression (increase in pressure) and the decrease in temperature during decompression (reduction in pressure). This can be important when treating children or very sick or intubated patients.

Increased amount of oxygen in the blood

The Henry’s law says that the amount of gas dissolved in a liquid corresponds at the partial pressure of this gas on the surface of this liquid. In the compressed chamber, more oxygen can be dissolved in the patient’s plasma than outside the pressure chamber.

Increased amount of oxygen in the tissues

Since the blood carries much more oxygen, it can supply the tissues with enormous quantities, especially where it is lacking. Then there are chemical reactions that trigger the healing process. This increased pressure causes oxygen to diffuse into the tissues and thus reaches areas with poor vascularity. The distance at which oxygen can diffuse from the last capillary is calculated with the mathematical diffusion model of Krogh

Claustrophobia occurs in about 3% of cases, in a monoplace chamber and in about 4% of patients in a multiplace chamber. From our own experience, we experienced a situation of claustrophobia in only 2% of patients. Often, patients get used to the hyperbaric chamber after a few treatments.

Side effects caused by pressure

Pressure damage to the middle ear
Between 13% and 17% dof patients complain of decreased hearing, ear pressure or severe ear pain. Symptoms go away within days without treatment or with nasal drops. Sometimes the treatment needs to be off for a few days.These side effects (Teed classification) can be avoided with a slow pressurization. If the patient has a cold or a flu, he will not be able to equalize. As a precaution, we stop the treatment until he is better.
Sinus pressure damage
This rarely happens. The exact figures are not known. In 30 years of our activity, we have never met such a case. The damage, mainly to the maxillary sinuses, usually occurs during decompression and manifests as pain and bloody nasal mucus. Treatment consists of slow decompression, nasal drops, and pain relievers if needed.
Pressure injuries to the lungs
Less than 1 per 100,000 treatments. We have never seen it in 35 years of activity. Caution is advised in patients who have previously had pneumothorax or in patients with pulmonary bubbles. If this happens, it is in the decompression phase. Treatment must take place in the hyperbaric chamber during the session with an appropriate drainage. Lung transplantation is not a contraindication for HBOT. Now done with the claims that HBO is harmful to the lungs.

Oxygen toxicity

Central nervous system
Only in the form of a grand mal type epileptic seizure. The frequency for patients without risk factors and a compression pressure of 240 to 250 kPa is between 1 attack per 12,000 to 14,000 compressions. As additional protection, we introduce oxygen pauses in the middle of the session . There are no sequelae and the EEG is normal. There is no individual brain hypersensitivity to oxygen. We note that the level of NO is suddenly increased just before the crisis which causes increased cerebral blood flow and consequently free radicals.
Up to 78% of patients develop temporary myopia after 40 consecutive treatments. This number is higher when patients inhale oxygen through a hood instead of a face mask . It is believed that this may be due to an opalescence of the lens which changes its refractive power. After a few months, the myopia disappears again, but there are traces of it that the patient does not realize. An ophthalmic examination is not necessary. Cataracts have been described after more than 100 consecutive treatments .


HBO immediately increases the partial pressure of oxygen in the blood and tissues.

In the open air, we cannot breathe more than 100% oxygen, in a medical hyperbaric environment the pressure can increase up to 3 times, which increases the amount of oxygen free radicals and of oxygen (up to 300%) and . This allows oxygen and their radicals to diffuse in the tissues better and further. Oxygen free radicals are mainly produced in cell mitochondria. These radicals lack an electron which makes them very unstable, it is why they will rapidly interact with enzymes, proteins, or genes in our body. It is this responsiveness that underlies most of the effect of HBOT. Due to their toxicity, free radicals immediately increase the production of free radical scavengers to achieve a protective balance.

Effect on bubbles

Carbon monoxide poisoning

Reperfusion injury

Cerebral gas embolism

Wound healing

Gas gangrene


Bone, cartilage, ligament formation

Bactericidal effect


Hyperbaric oxygen therapy is supported in ambulatory (TARMED) and hospital (DRG) settings for the following situations:

Chronic diabetic wounds
Damage by anti-cancer radiation
Chronic osteomyelitis
Osteomyelitis of the jaw
Decompression sickness

Despite the fact that scientific data are rather more in favor of hyperbaric oxygen therapy for the following indications, there is no coverage by the Swiss health funds while this is sometimes the case in other countries. This somewhat outdated list follows 2016 guidelines from the Tenth European Consensus Conference on Hyperbaric Medicine.

Aseptic femoral head necrosis
Sudden deafness
Acoustic traumatism

HBOT and hospital medicine. HBOT is part of hospital medicine in many hospitals worldwide. HBOT plays an important role in managing various diseases or serious accidents. We mention gas gangrene, necrotizing fasciitis, cerebral gas embolism, acute central retinal artery occlusion, secondary infections and serious diving accidents. These patients require intensive and multidisciplinary care and HBOT is one of them.

Critically ill patients cannot be transported back and forth to a hyperbaric center on a daily basis. They must therefore be transferred to a clinic where HBOT is part of hospital and intensive care medicine. These patients require multidisciplinary care and sometimes prolonged intensive care because of their multiple pathologies.

These hospitals must have their own hyperbaric chamber equipped for intensive care. The intensive care staff are trained to work under compressed air.

The hyperbaric chamber constantly requires safe and optimal operation. This staff consists of a hyperbaric chamber technician, a hyperbaric doctor and nurse and finally a safety officer with full powers to stop ongoing treatment if safety requires it.

Hyperbaric intensive care at Karolinska Hospital

In Switzerland, these conditions are only met at the university hospitals in Geneva, since the hyperbaric chamber in Basel is only  designed for outpatients.
Cerebral gas embolism
Necrotizing fasciitis
Acute CO poisoning

For emergency outpatient treatment such as decompression sickness, the TARMED position 15.0380 is used, corresponding to an hourly rate of 450.36 francs. Such a first treatment usually lasts 5 hours, additional treatments if necessary usually last 2 hours.

For non-urgent treatments, we use the TARMED position 15.0370. Depending on the tax point value, a session currently costs CHF 243.76.
For hospitalized patients, the treatment costs are included in the hospital package. Hospitals can charge insurances for the extra costs caused by HBOT by using the following positions.

We have completed our research program in collaboration with the University of Basel on the treatment of stroke sequelae with hyperbaric oxygen. Our work, approved by swissethics can be obtained here.

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