HBOT – Hyperbaric Oxygen Therapy: scientific definition and bibliography

Hyperbaric Oxygen Therapy (HBOT) is the bloodless administration of pure oxygen or gas mixtures enriched with oxygen that occurs in special environments, that is hyperbaric chambers that are brought to a pressure superior to atmospheric pressure through compressed air pressurization, while the patient breaths pure oxygen or gaseous mixtures inside the chamber in a closed-loop, through masks, helmets or endotracheal tubes.

In air breathing, at atmospheric pressure, the 98.5% of oxygen is transported by red cells that contain haemoglobin which links to oxygen; therefore it is necessary to have complete blood vessels to red cells passage to facilitate oxygen arrival to tissues. At 2 and 3 absolute atmospheres (ATA), the quantity of oxygen carried to tissues, in this form, can be even 15 times more than normal, in order to entirely facilitate cells’ necessities.

This oxygen increase, dissolved in the physical form in the plasma, implies the possibility to restore oxygenation in areas where blood vessels are reduced or deficient, therefore in hypoxic or hypo perfused areas. It implies the recovery of oxygen-dependent tissue functions, the possibility to contrast toxic effects that resulted in tissue hypoxia. It increases the deformability of red cells and therefore their ability to move inside blood vessels, capillaries included.

  1. It involves redistribution of blood through hypoxic tissues following vasoconstriction in healthy tissues. Besides these effects, hyperbaric oxygen has a direct and indirect antibacterial function, a vasoconstriction action with reduction of the post-traumatic and/or post-surgical oedema, it protects tissues from ischemia/reperfusion damages, by maintaining normal levels of ATPase, phosphocreatinkinasis and low levels of lactates. It protects membranes from radical lipid peroxidation, it inhibits the production of beta2 integrins that favour leukocytes adhesiveness on the capillary wall, with consequent endothelial damage.
  2. It promotes the reparation processes with the increase of the cellular metabolism, the fibroblasts, osteoblasts and collagen synthesis reactivation, it increases the extracellular matrix synthesis and it stimulates the 3-7 vascular neoformation.

HBOT is used in morbid states where there is a local imbalance between necessity, contribution and ability to use oxygen: acute or chronic cardiovascular failures, bone diseases, acute or chronic bone and soft tissues infections. In order to make hyperbaric oxygen action effective, a certain amount of time and sessions are needed, that vary according to the type of disease to be treated (acute or chronic), of the tissue affected by the disease (bone tissue, for instance, needs more treatment compared to other tissues) and of the association in the same disease of more debilitating causes (i.e.: in diabetic foot the seriousness of the local situation is worsened by the presence of ischemia and infection).

The reactivation of vital functions, such as cellular respiration, with consequent activation of the tasks the cell is designated, the vascular neoformation etc. are all effects the hyperbaric oxygen carries out during time also after the end of the therapy.

Bibliography
1. Mathieu D, Coget JM, Vinckier L, Saulnier F, Durocher A, Wattel F. Filtrabilité érythrocitaire et oxygénothérapie hyperbare. Med Sub Hyp 1984; 3:100-4.
2. Thom SR. Effects of hyperoxia on neutrophil adhesion. Undersea Hyperb Med 2004; 31:123-31.
3. Niinikoski J. Effect of oxygen supply on wound healing and formation of experimental granulation tissue. Acta Physiol Scand Suppl 1969; 334:1-72.
4. Niinikoski J. Viability of ischemic skin in hyperbaric oxygen. An experimental study with rats. Acta Chir Scand 1970; 136:567-8.
5. Niinikoski J, Hunt TK. Oxygen and healing wounds: tissue-bone repair enhancement. In: Wattel F, ed. Handbook of Hyperbaric Medicine. Milan: Springer-Verlag, 1996:485-597.
6. Niinikoski J. Current concepts of the role of oxygen in wound healing. Ann Chir Gynaecol 2001; 90 Suppl 215:9-11.
7. Hunt TK, Niinikoski J, Zederfeldt B. Role of oxygen in repair processes. Acta Chir Scand 1972; 138:109-10.
8. Mathieu D, Linke JC, Wattel F. Non-healing wounds. In: Mathieu D, ed. Handbook on Hyperbaric Medicine. Dordrecht (NL): Springer, 2006:401-27.