Hyperbaric chamber

What is it

The Hyperbaric Chamber is an environment that can be pressurized with air and/or a mixture such as to increase the internal pressure in a verifiable way, of such thickness as to withstand pressures higher than those of exercise and used to house people, it can be fixed and mobile, single-seater and multi-seater.

The Hyperbaric Chamber complies with the definition of type II B devices and is framed in the EEC directive of 14.06.1993 relating to medical devices.

Hyperbaric chambers can be classified, based on their use, in:

  • Hyperbaric Health Chambers: located in all public and private health facilities;
  • Working Hyperbaric Chambers: located in workplaces and used only in emergencies and urgencies such as underwater construction sites both onshore and offshore, or in construction sites such as tunnel constructions (motorways, subways, marine underground tunnels, etc.) using tunnel-digging machines that work in a hyperbaric regime (at pressures higher than the environmental pressure).

The Hyperbaric Chamber must be of a size that allows the stay of a patient on a stretcher with the possibility of assistance by suitable health personnel and must be equipped with a reserved area for rapid access by staff.

During the treatment inside the room, once the predetermined altitude for the specific therapy is reached, the patient will breathe pure oxygen (or a hyperoxygenated gaseous mixture) in a closed circuit, using a device customized to the specific case (orofacial mask, helmet, mount or mechanical ventilation).



The use of OTI is for the indications recognized by the Guidelines* and by Evidence-Based Medicine (the EBM of the AA.) and has to be carried out only in full compliance with the safety regulations in force for pressure vessels, as in fact it is the hyperbaric chamber.

When delivered safely and for recognized indications, and provided that a careful assessment of the risk/benefit ratio of this procedure is made during the access visit/suitability for treatment, OTI is usually well tolerated and free of complications, even in critically ill patients.

The hyperbaric doctor will evaluate the feasibility of treatment with OTI on the basis of the relationship between the “number of sessions to be performed” and the “relative risk” of the individual case.


The effectiveness of hyperbaric treatment essentially depends on two factors:

  • Increase in barometric pressure
  • Increase in partial pressure of O2

Dissolved oxygen is used in three circumstances:

  • In the original circulatory defect (transport), replacing the oxygen transport by means of hemoglobin, when it is deficient due to lack (anemia) or functional incapacity (carbon monoxide poisoning)
  • Circulatory defect of “ischemic” origin by restoring the diffusion of oxygen from the capillaries to the cells when blood perfusion is obstructed or decreased (ischemia)
  • Circulatory deficit of “edematous” origin due to thickening of the means of transit (edema of any nature, pyogenic, cerebral, medullary and tissue membranes edema)

This mechanism defines the increase of the partial pressure of oxygen (PO2) which is expressed in different ways:

1. Brings greater availability of oxygen to the periphery

2. It nourishes the areas lacking in oxygen (hypoxia) and determines the resumption of functions dependent on precise therapeutic “ranges”.

In particular, the pharmacological action of oxygen determines:

  • Activities on reparative processes
  • Osteogenic stimulation action
  • Bactericidal and/or bacteriostatic activity
  • Action on the arterial and venous circulation
  • Restoration of the previously insufficient biochemical substrate
  • Tissue resuscitation
  • Toxicity


The mechanism of action of hyperbaric oxygen derives from the application of physical gas laws (Boille-Mariotte, Henry, Dalton) which regulate tissue absorption and diffusion, and from principles of oxygen physiology up to its application in the field of pharmacology.

The administration of oxygen, in fact, is based on the principle of the solubility of a gas dissolved in a fluid; in our case the gas is represented by O2 and the fluid is the blood.

Henry’s law states that the amount of a gas that dissolves in a liquid is directly proportional to the pressure the gas exerts on the surface of the liquid and to its solubility coefficient.

A subject, to the current ambient pressure (760 mmHg or 1 ATA) breathes air formed by O2 at 21% and N2 at 79%.


In normal conditions and at normobaric pressure, oxygen is transported by red blood cells bound to hemoglobin (Hb) for 97%. It is known from physiology that one gram of Hb carries 1.34 ml of O2 per 100 cc of blood and that the amount of Hb transported in 100 cc of blood is 15 grams. It can be said, therefore, that the quantity of O2 transported by the red blood cells is 19.7 ml per 100 cc of blood, while the quantity of O2 physically dissolved in the plasma is 0.32 ml. per 100 cc of blood (See Table).

In normobaric conditions, breathing of oxygen at 100% (FiO2 = 1) determines minimal changes in the oxygen linked to hemoglobin which passes from values ​​of 19.7 to 20.1 ml per 100 cc of blood, while the amount of O2 dissolved in the plasma passes from 0.32 to 2.09 ml per 100 cc of blood (Tab. 1).

In hyperbaric conditions, at a pressure of 2.0-2.8 ATA, breathing of oxygen at 100% (FiO2 = 1) causes an increase in oxygen partial pressures up to values ​​of 1560-2280 mmHg.

The O2 bound to hemoglobin in hyperbaric conditions, according to Henry’s law, does not experience variations, while the free share in the plasma has a significant increase from 0.32 ml. for 100 cc. of blood to 6ml. for 100 cc of blood (See Tab.)

This amount of oxygen is sufficient to meet cellular metabolic demands, resulting in a “tissue resuscitation” regardless of the oxygen content linked to hemoglobin. This is the main mechanism on which hyperbaric oxygen acts. Tissue oxygenation is therefore maintained even in conditions of modified transport of O2 linked to hemoglobin.

Chest X-ray in two projections
E.C.G. baseline
Audio-Impedance measurement
Further investigations to be defined based on the pathology

* Israeli studies, still in progress, have highlighted indications for OTI in Fibromyalgia.

In Italy, some Hyperbaric Centers have taken steps to carry out the therapy in Fibromyalgia to verify its effectiveness. The therapy is currently considered Off Label and the results obtained encourage us to treat patients with fibromyalgia with OTI.

in-depth analysis and details


The clinical indications for hyperbaric oxygen therapy are based on the analysis of the scientific literature and in particular on what emerged from the documents of SIAARTI (Italian Society of Anesthesia, Analgesia, Intensive Care and Intensive Care), and SIMSI (Society of Underwater and Hyperbaric Medicine).

Document of the UHMS (Undersea and Hyperbaric Medical Society) Committee Report Documents of the Consensus Conference of the ECHM (European Committee for Hyperbaric Medicine).

The European Committee for Hyperbaric Therapy is committed, together with the national scientific societies, to improving knowledge, qualities and cultural exchanges; moreover, to promote ideas and research programs and to harmonize indications and operational protocols.

The use of OTI is to be addressed for the recognized indications and to be carried out only in full compliance with the safety standards in force for pressure vessels, in particular for hyperbaric chambers.

The access visit/suitability for treatment requires a careful assessment of the risk/benefit ratio of this procedure. The hyperbaric doctor will evaluate the feasibility of treatment with OTI on the basis of the relationship between the “number of sessions to be performed” and the “relative risk” of the individual case.


  1. Decompression Pathology (EGA, MDD)
  2. Progressive Necrotizing Infections (Anaerobic myositis, necrotizing fasciitis, necrotizing dermo-epidermal infections, diabetic gangrene)
  3. Carbon monoxide poisoning
  4. Crushing/traumatic injuries and fractures at risk
  5. Skin grafts and flaps at risk
  6. Sudden hearing loss


    1. Chronic refractory osteomyelitis
    2. Chronic skin ulcers
    3. Post-actinic tissue lesions
    4. Diabetic foot
    5.  Aseptic osteonecrosis

Other Indications


  1. Periodontal disease
  2. Algodystrophy syndrome
  3. Retinitis Pigmentosa – Central artery ischemia of the retina
  4.  Ménière’s disease
  5.  Osteonecrosis of the mandible due to bisphosphonates
  6.  Fibromyalgia * (Currently not included in the SIMSI guidelines)
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