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Hyperbaric oxygen for chronic wounds

Systematic review
Results
Comment

Chronic wounds that take a long time to heal, or which recur, are quite common, particularly in older diabetics and people in hospital, and those with multiple health problems. Wound management varies according to the underlying cause of the wound, and there are many options. Despite adequate treatment, some wounds fail to improve, or actually get worse. In some cases, particularly in diabetes, amputation becomes necessary.

Using hyperbaric oxygen to increase oxygenation of tissue and stimulate healing has been proposed, and is used. It is expensive because it involves placing patients in a hyperbaric chamber filled with pure oxygen at pressures above one atmosphere for up to two hours. The procedure is often repeated once or twice a day for up to 30 such sessions. A systematic review of small studies [1] gives a strong hint that there may be real benefits.

Systematic review

Trials had to include a randomised comparison of hyperbaric oxygen therapy compared with sham therapy on air or no therapy for chronic wound healing. Chronic wounds could be related to diabetes, or venous or arterial disease, or pressure. Outcomes were predetermined, as wound size reduction, proportion healed, major amputation (lower or upper limb proximal of hand or foot), minor amputation (distal end of hand or foot), pain, recurrence, or quality of life, together with adverse events. Several electronic registers were used, including a specific database for RCTs in hyperbaric medicine. The last searches were in 2003.

Results

Six randomised trials were found, five in diabetes and one in venous ulcers, with 191 patients, of whom 100 received standard treatment plus hyperbaric oxygen, while the controls received standard wound treatment alone, or with additional sham therapy on air (three trials). Methodological quality was adequate in three, mainly due to issues around blinding and use of sham therapy. Short duration of follow up was also an issue in some trials.

The main results are shown in Table 1. Significant improvements were found for wound size reduction soon after therapy, and for major amputation (Figure 1), where the relative risk for major amputation with hyperbaric oxygen therapy was 0.3 (0.1 to 0.7), and the number needed to treat to prevent one major amputation was 4 (2.7 to 12).



Table 1: Main outcomes of randomised trials of hyperbaric oxygen therapy for chronic wounds



Outcome
Studies
Results
Wound size reduction
2
Both studies (one venous ulcer) measuirng wound found significant reduction soon after therapy
Proportion healed
3
In diabetes, 7/24 healed with hyperbaric oxygen vs 1/22 for control, though not significant. No gignificant improvement in the venous ulcer trial
Major amputation
3
In diabetes, significant reduction in the two largest trials, and overall. NNT 4 (3-12)
Minor amputation
2
In diabetes, 5/24 with hyperbaric oxygen vs 2/24 for control, with no significant difference




Figure 1: Major amputations with hyperbaric oxygen and control





Adverse events were noted in some trials. Two cases of pressure trauma to the ear were recorded.

Comment

The use of hyperbaric oxygen for wound healing is a grey area. Some non-randomised studies suggest a moderate benefit, and the small randomised studies appear to confirm that for diabetic ulcers, notwithstanding methodological problems about blinding and follow up. Major amputation is a hard clinical outcome, and it lends weight to the conclusion. There is no more evidence, and additional searching in 2005 found no more randomised trials.

There is obviously scope for bigger and better trials, and for some health economic consideration. It may be expensive for four patients to have 20-30 sessions of hyperbaric oxygen therapy, but the cost and burden of the one major amputation avoided is also likely to be substantial. Even a cursory consideration of the relative costs suggests that balance is likely. It should not be too difficult to determine break points at which effectiveness of treatment is cost effective, or even cost saving. In the meantime this review will provide useful information for purchasers of therapy.

Reference:

  1. I Roeckl-Wieddmann et al. Systematic review of hyperbaric oxygen in the management of chronic wounds. British Journal of Surgery 2005 92: 24-32.

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