Hyperbaric Oxygen Treatment (HBOT) most commonly refers to the delivery of increased levels of oxygen at greater than ambient pressure for a prescribed duration of usually 60 to 90 minutes in an, specially designed enclosed chamber.
This process causes oxygen to be absorbed by all body fluids and by all body cells and tissues, even those with blocked or reduced blood flow.
This increased flow of oxygen stimulates and restores function to damaged cells and organs.
The air we normally breathe contains 21% oxygen, 78% nitrogen, with the remaining 1% being contributed by the noble gases and carbon dioxide. The concentration of these gases is determined by the atmospheric pressure which is determined by the weather and is reduced at altitude. Unfortunately the variations in this pressure are ignored in general medical practice. Atmospheric pressure is accorded the unit 1 to represent atmospheric pressure absolute (1 ata) and this unit is divided according to the percentages of the gases in air to give their 'partial pressures' that is the part of the total pressure each gas is responsible for - oxygen therefore being 0.21 ata (21% of 1) and nitrogen 0.78 ata (78% of 1).
How does breathing more oxygen help?
The air that we breathe usually provides enough oxygen for both normal body metabolism and repair to tissue damage after injury or illness. However increasing the pressure surrounding a patient in a hyperbaric chamber and using 100% oxygen can allow a very significant increase in the amount of oxygen dissolved in the bloodstream. This is in addition to the oxygen carried by haemoglobin. Normally the amount carried dissolved in plasma is about 0.3 ml per 100 ml of blood.
At twice atmospheric pressure (2 ata) breathing 100% oxygen this increases to 3 ml oxygen in 100ml of blood. The increased concentration means that the gradient for the transport of free oxygen from blood into the tissues is increased 10 fold.
When tissues are damaged the capillaries within the tissues are also damaged which increases the distances for oxygen to diffuse. This can lead to a severe oxygen deficit in the tissues even when the amount of oxygen carried in the blood is normal. The object of using the increase in pressure and oxygen concentration is to raise tissue oxygen values towards normal to initiate normal cellular repair mechanisms. In fact oxygen, like glucose and water is an essential substrate.
How does HBOT lead to tissue recovery?
Oxygen is dissolved in the blood and transported, in combination with haemoglobin in the red blood cells throughout the body. This dissolved oxygen passes into the tissues. Breathing high levels of oxygen under hyperbaric conditions causes greater uptake of oxygen by the bodily fluids and so more can reach areas where the circulation is diminished or blocked and therefore improve recovery. The extra oxygen has additional benefits as it greatly enhances the ability of white blood cells to kill bacteria. It also reduces swelling and allows new blood vessels to grow more rapidly into the affected areas.
Severe tissue hypoxia (oxygen deprivation) has many adverse effects from abolishing normal cell activity as, for example, with loss of consciousness to disabling white blood cell activity in infection. Only the administration of oxygen can 'treat' hypoxia and the objective of the administration of oxygen is to establish tissue oxygen values compatible with the initiation of normal healing.