Treating wounds with oxygen: treating wounds with oxygen has a long history. But hyperbaric oxygen treatment is still an under-used resource in wound care, particularly in the care of chronic wounds.

Hyperbaric oxygen treatment (HBOT) has come a long way since a British clergyman built the first chamber in 1662. (1) In 1939 diving injuries began to be treated with hyperbaric oxygen, medicine started to use it in 1955, and in the 1970s the Underwater Hyperbaric and Medical Society (UHMS) began to systematically review the evidence available on hyperbaric medicine. (1) Clinicians in the flew acknowledge more research on HBOT is needed andresearch studies are underway in several countries.

In New Zealand there are just three hyperbaric oxygen treatment units: The Devonport Naval Base and The Oxygen Therapy Clinic, both in Auckland; and the Hyperbaric Medicine Unit in Christchurch; thus access to this treatment is limited. The Oxygen Therapy Clinic and the Hyperbaric Medicine Unit are both private clinics.

Hyperbaric oxygen treatment involves placing patients in either a mono- or multi-place pressurised chamber. In the multi-place chamger patients have the option of wearing a clear plastic hood into which the oxygen is delivered, or a mask which is strapped around their head. The chamber is pressurised to the equivalent of 14 metres underwater and it is this pressure which forces oxygen into the blood vessels and tissues.

The majority of patients at The Oxygen Therapy Clinic are those with chronic wounds, those who have had radiation therapy and those who are having or who have had head and neck surgery. As this is often reconstructive surgery involving skin flaps and grafts, it is important tissue is well oxygenated before surgery.

There are many patients we could assist before their wound becomes chronic. Those with diabetes ulcers are a prime example. Hyperbaric oxygen treatment is also useful for injuries that create hypoxic wounds even in healthy people, eg the white tail spider bite.

The UHMS has written guidelines based on evidence-based research, which state what groups of patients have been proven to benefit from the treatment. (2) These are patients suffering decompression illness; arterial gas emboli; gas gangrene; CO poisoning; crush injuries; "problem" wounds; exceptional anaemia (significant blood loss in those unable to receive transfusions); intercranial abscess; necrotising soft tissue infections; osteomylitis; radiation injury; skin grafts and flaps; and thermal injuries.

The term "problem wound" may not be strictly scientific but it is a helpful classification, as it includes all those wounds that don't seem to respond to treatment. Hyperbaric oxygen treatment does not take the place of wound care; rather, it is adjunct to it. A patient beginning HBOT can have their wound care at the clinic or the wound care can remain with their primary provider. This is usually discussed with the staff involved when a patient is accepted for HBOT. Hyperbaric oxygen treatment has been demonstrated to do many things which are advantageous to wound healing. These include fibroblast activation, reduction of inflammatory cytokines and leukocyte chemotaxis; encouraging growth factors, potentiation of antibiotics and it is also has an antibacterial effect. (3)

The treatment has to be used in the correct circumstances to ensure its efficacy. This can be ascertained by monitoring the limb and the peri-wound tissue with a transcutaneous oxygen monitor. For HBOT to be effective, the main arterial routes have to be intact and free from disease, so they can deliver the oxygenated blood. If the smaller vessels nearer the wound are narrowed by disease or trauma, then the high pressure of oxygen delivered in the chamber when having HBOT can overcome this. (4) Leucocytes and macrophages become more effective when oxygen is added to the wound, hence the importance of HBOT in an infected wound. To enhance this effect, HBOT reacts synergistically with a range of antibiotics to increase their effectiveness,s It reduces oedema, because the oxygen has a vasoconstrictive action on the damaged, leaking vessels, which prevents further leakage of fluid from the capillaries into the tissues. (4) As the high-pressure oxygen is pushed into capillaries, the surrounding tissues, which have been starved of oxygen, become well perfused. In turn, the transference of nutrients between the capillaries and the tissues becomes easier. HBOT also improves uptake of some growth factors, which enhances granulation tissue formation. (4,5) Hence, the effects of HBOT are three fold: it adds oxygen to a wound environment which is hypoxic due to poor blood supply; it reduces oedema so the oxygen-rich blood can reach the tissues; and it enables the white blood cells to protect the wound against infection more effectively. (6)

Referrals to the clinic can be done by filling in the referral form on-line at www.hbot.co.nz. The clinic's hyperbaric physician will then make contact, discuss the patient, set up assessments and, if applicable, organise funding. Funding can be provided from several sources.

The Accident Compensation Corporation (ACC) will fund some injuries, so it is important to ensure all injuries are documented and filed, despite how minor they may appear. This is particularly important for those with diabetes or any patient who has the potential for slow healing. Some district health boards will provide funding, if it is recognised the time a patient is either in hospital or receiving out-patient care, will be reduced by HBOT. There are other funding options which can be pursued if the patient does not fall into either of these categories. Some health factors eliminate certain patients from HBOT and this is why a thorough assessment is done before treatment. Some respiratory conditions, for example where the airways are narrowed and expiration is difficult, preclude HBOT. Some chemotherapy drugs are incompatible with HBOT.

References

(1) KindwelI, E. and Whelan, H. (1999) Hyperburic Medicine Practice. Best Publishing Company: Flagstaff, United States.

(2) Feldmeier, J. (2003) Hyperbaric Oxygen, Indications and Results. Underwater and Hyperbaric Medical Society: Maryland, United States,

(3) Kranke, P., Bennet, M., Roeckl-Wiedmann, I., Debus, S. (2004) Hyperburic oxygen for chronic wounds. The Cochrane Database of Systematic Reviews. www.cochrane.org/index@.htm (Retrieved August 2005)

(4) Wright, J. (2001) Hyperbaric oxygen therapy for wound heating. World Wide Wounds, May 2001.

(5) Broussard, C. (2004) Hyperbaric oxygenation and wound heating. Journal of Vascular Nursing; 22, 42-48.

(6) Frykberg, R. (1991) The High Risk Foot in Diabetes Mellitus. (1st ed.) New York: Churchill Livingstone.

This article was reviewed by Koi Tioki Nursing New Zealand's editorial review committee in December 2005.

Helen Polley, RN, PGCert, ENB264, is the wound care and hyperbaric nurse at the Oxygen Therapy Clinic in Auckland.