Family doctor

What is it?

Hyperbaric Oxygen Treatment or HBOT is the administration of 100% oxygen under increased atmospheric pressure (usually 2 atmospheres or 10 metres sea water). It is widely used internationally to treat a range of clinical conditions that notoriously respond slowly to conventional treatment. The patients are treated in a large 8 person double lock steel chamber with a hyperbaric nurse always present.

What conditions is it used for?

The clinical indications approved by the Undersea and Hyperbaric Medical Society (UHMS) include:

• Air or gas embolism
• Carbon monoxide poisoning and smoke inhalation
• Clostridial myonecrosis (gas gangrene)
• Crush injury, the compartment syndrome, and other acute traumatic ischaemias
• Decompression sickness
• Enhancement of healing in selected problem wounds (including cellutitis, arterial/venous and diabetic wounds etc.)
• Exceptional anaemia resulting from blood loss
• Necrotising soft tissue infections (of subcutaneous tissue, muscle, or fascia)
• Refractory osteomyelitis
• Radiation tissue damage (osteoradionecrosis)
• Compromised skin grafts and flaps
• Thermal burns
• Cerebral (brain) abscess

There is slowly accumulating evidence to support its use in the following area as well:

• Sports injuries/soft tissue injuries
• Peripheral vascular disease, ischaemic leg pain
• Rehabilitation of head injury/stroke
• Sudden blindness (central retinal artery/vein occulsion)
• Vascular headaches
• Sudden deafness and acute acoustic trauma
• Non-healing fractures, bone grafts
• Enhancement of rediosensitivity of malignant tumours

How does it work?

The mechanisms of action of HBOT which accounts for its success in the above conditions are:

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.

Effects on the microcirculation:

High-pressure oxygen causes vasoconstriction in normal tissues while maintaining oxygenation. This narrowing does not occur in injured, ischaemic tissues. HBO is therefore extremely useful in crush injuries and other traumatic ischaemias.

HBO also markedly reduces adherence of white cells to capillary walls thus preventing ischaemia-reperfusion injuries or the "no reflow" phenomenon. Oedema is reduced up to fifty percent through preservation of high-energy phosphate bonds (ATP) in the cells. Oxygen diffuses two to three times as far from capillaries into tissues when breathed under pressure. This keeps injured tissue with sparsely functioning blood vessels alive. Preservation of ATP is also important in preventing progression of deep second-degree burns to full-thickness injury requiring grafting.

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.

Getting help

HBOT can be accessed in Auckland, New Zealand at The Oxygen Centre, Takapuna. Ph 09 489 7142. E-mail: admin@hbot.com.

Patients are screened by the Centre's doctor for both suitability of their condition and their fitness to receive HBOT. (There is only one absolute contraindication and that is untreated pneumothorax).