Hyperoxygenation:
HBO physically dissolves extra oxygen into the plasma and tissues. Breathing pure oxygen at twice atmospheric pressure increases the tissue oxygen pressure in compromised tissues to normal or greater-than-normal values. It then induces the formation of new capillaries in ischaemic or poorly perfused wounds due to the extreme oxygen gradient between the well-oxygenated and hypoxic areas.

Antibacterial activity:

HBO inhibits the growth of a number of anaerobic organisms and enhances white cell killing of aerobic organisms. HBO can double or triple the bacteria-killing ability of white cells. It is particularly useful in patients where resistance factors are compromised. HBO acts synergistically to most antibiotics and even potentiates the bactericidal effect of aminoglycosides.

Air or gas embolism:
HBO is the undisputed primary treatment for air embolism. It decreases bubble size and hastens the resolution of the embolised gas. It reduces mortality and minimises permanent neurological damage. There is no effective alternative therapy. Causes of air embolism include lung overpressure injuries during scuba diving, open heart surgery, neurosurgery, certain radiological procedures, arthroscopy, etc.