Hospitals & Services
Associate Professor (ret’d) F Michael Davis, formerly Medical Director, Hyperbaric Medicine Unit, Christchurch Hospital
Hyperbaric oxygen therapy (HBOT) is the intermittent administration of 100% oxygen at pressures greater than normal ambient pressure. There are several ways to provide this, all of which require a pressure vessel in which the patient(s) sit or lie for 2–3 hours daily for several weeks.
Six small, prospective randomised trials of HBOT for diabetic ulcers have been published.1–6 All show improved healing and, in two, a reduction in major amputation rate was reported (Table 1). Follow-up studies suggest these benefits are maintained in the medium to long term (3–5 years).8 However, a recent Cochrane review concluded there was a need for further large randomised studies because the trials (Table 1) had various flaws in design and/or reporting not meeting Cochrane criteria.9
HBOT is a moderately expensive treatment. In Christchurch, the estimated cost of a 30-treatment HBOT course is approximately $12,000 per patient. However, the cost-benefit studies from the UK and USA show an overall saving by combining HBOT with standard modalities of care in the management of diabetic ulcers, as well as improved outcomes.4,8 The UK study reported an overall saving of approximately NZ$8,000 per patient treated compared to non-HBOT care.4
Locally, we have too small a database yet to have a good idea of how well we are doing. However, of the first 50 lower limb ulcers of mixed aetiology (approx. half DM ulcers) referred to HMU, 18 (36%) were healed and 7 (14%) substantially improved on medium-term (approx. 3 month) follow-up (NNT for improvement = 2). There has been no major morbidity from HBOT in these patients. An on-going prospective cohort Australasian study of HBOT for problem wounds, both diabetic and non-diabetic, with over 400 cases shows a similar early post-HBOT healing rate, increasing to over 75% at one year, irrespective of the aetiology. Despite the Cochrane conclusions, we are firmly of the view, from our local clinical experience that HBOT, combined with multidisciplinary wound care improves healing in selected patients.
There are diverse actions of HBOT, including support of oxygen-dependent healing processes and, more importantly, cell-signalling effects that accelerate these processes for many hours beyond the HBOT exposure. The intermittent restoration of steep oxygen diffusion gradients in the peri-wound area stimulates fibroblast function in a dose-dependent manner.10,11 The cyclical pattern of hyperoxygenation/hypoxia leads to the release of local humoral mechanisms promoting wound healing. Recent work suggests a positive effect on nitric oxide metabolism in the diabetic wound. These changes result in an advancing field of neovasculogenesis. At the same time, oedema is reduced improving perfusion, and macrophage function is enhanced, particularly the ‘oxygen burst’ phase, in the hypoxic diabetic wound. HBOT is known to work synergistically with several antibiotics. Daily HBOT also corrects deficient neutrophil adhesion in Type II diabetes.
Any diabetic patient in whom a wound is not healing after a reasonable period of multidisciplinary wound care should be considered for HBOT. The international consensus is that an ulcer failing to respond after six weeks (or earlier, if the ulcer is limb-threatening) and for which no correctable large vessel disease is present should be referred for assessment for HBOT. Renal failure and concomitant major arterial disease carry a poorer prognosis for healing with HBOT just as they do with other interventions. Anecdotally, HBOT has been reported to be particularly useful in the neuropathic and Charcot foot.
The evidence in non-diabetic ulcers is more limited than for diabetic ulcers, but the same broad principles apply and HBOT has been shown to enhance healing in one small, prospective, randomised study.7
Problem wounds secondary to accidental trauma or medical misadventure in both diabetic and non-diabetic patients may be referred for assessment for HBOT under a prior approval ACC contract that has been in place nationally since March 2002. Many potential referrers are still unaware of this ACC-funded service.
Referrals to the Hyperbaric Medicine Unit at Christchurch Hospital may be made directly from primary care.
There are clinical HBOT facilities in Christchurch and Auckland, at the RNZN Medical Centre and at Quay Park Medical Centre. The only hyperbaric facility in New Zealand based in a civilian, tertiary-referral hospital is at Christchurch Hospital.
Table 1. Summary of randomised studies of hyperbaric oxygen therapy in diabetic and non-diabetic ulcers
Healed ulcer at 1yr
Wound area decrease
Wound healing time