Asked by: Lorraine Musa, Bristol
Answered by: Simon Wilson, technical director, London Diving Chamber, Hospital of St John and St Elizabeth, London
How did air pressure become used as a medical treatment?
Hyperbaric Oxygen Therapy (HBO) is a treatment which involves administering oxygen to patients while they are in a decompression chamber, the type most commonly associated with deep sea divers and treatment of decompression illness "the bends". Research started in the 1960s and 1970s and was mainly carried out by the US Navy and the Undersea and Hyperbaric Medicine Society which now lists around 13 different conditions helped by HBO therapy.
How does it work?
A patient will typically sit in the chamber for 90 minutes and the atmosphere will be compressed to around two and half times atmospheric pressure. Apart from periodically "popping" their ears, patients should feel no physical effect. Once the compression level has been reached the patient is given pure oxygen to breathe.
Why does it work?
Every cell in the body needs oxygen to survive and to heal. Under compression, breathing 100 per cent oxygen means that the vital gas is distributed into the body on a cellular level more effectively and more oxygen dissolves into the blood plasma. The body thus becomes "super-oxygenated" and as a result oxygen can be carried to places in the body where it does not normally reach. Capillaries grow again and tissue that has been dead even for many years can be restored. The two facets of the treatment, compression and oxygen, have to be administered in unison. Compression itself will have little physiological effect and, even if breathing pure oxygen, the body will only metabolise around 30 per cent of the gas under normal atmospheric conditions.
What can it treat?
In addition to decompression illness and carbon monoxide poisoning, HBO therapy is used to treat arterial gas embolisms, slow-healing, infected wounds, arterial insufficiencies such as central retinal artery occlusion, severe anaemia and certain types of necrosis, such as necrotising fasciitis. Together with the Royal Marsden Hospital there is now a study being done into the effectiveness of HBO therapy for pelvic cancer patients suffering post-radiation therapy damage. The treatment is also used by many MS sufferers and although there is no conclusive evidence that HBO therapy can alleviate the condition, there is no denying some find it can alleviate symptoms. It is also used electively by many sports professionals for injuries and recovery. Top athletes will use a chamber after an endurance competition, such as a marathon, to help them recover quicker.
What conditions has it the potential to treat?
As well as the Royal Marsden study on cancer patients there have also been positive studies into the effect HBO therapy has on liver regeneration. However, the main growth area for hyperbaric oxygen treatment in the coming years will be on treating diabetes. The condition causes poor circulation in lower limbs and as a result patients are prone to ulcers and lesions which are difficult to heal and frequently lead to amputation. HBO is effective in treating these wounds and as diabetes rates rise, it will become increasingly important. In countries where HBO therapy is part of the healthcare culture, surgery for diabetic wounds is much lower than in the UK. In the US and Australia, it is a common treatment and many hospitals have a hyperbaric chamber. In the UK there are only around 12.
Interview by Nick Harding