The role of hyperbaric oxygen in chronic wound treatment

To better understand the effect of hyperbaric oxygen therapy (HBOT) in the treatment of chronic wounds, it is important to understand what a chronic wound is, what its "problem" is, and at what stage of treatment HBOT comes into play.

There are numerous definitions of a chronic wound in which arbitrary time values and certain procedures are taken, but all definitions can be put under the "hood" of the following: A chronic wound is any wound that does not heal within the expected period of time.

Wounds go through certain stages during healing. During each of them, there is a possibility of problems that will result in the cessation of healing.

There are many possible problems, the main ones being infection, devitalized, dead tissue that has not been removed and is a place for bacteria and other microorganisms to accumulate, mechanical injury due to constant external pressure (e.g. inadequate footwear), and lack of oxygen due to poor blood circulation.

We suppress infection with antimicrobial drugs such as antibiotics, dead tissue is removed by a skilled surgeon's scalpel, external pressure is removed by unloading, and lack of oxygen (hypoxia), this crucial factor is corrected by its delivery, and it is precisely in these "boots" that hyperbaric oxygenation steps in as one of the most effective suppliers of oxygen.

By including HBO therapy in the treatment of chronic wounds, especially in patients with diabetes and circulatory diseases:

• the need for limb amputation is significantly reduced and disability is prevented,
• the inhibited healing mechanisms are unblocked by delivering oxygen to tissues that are deficient in it,
• the formation of new blood vessels, stem cells and growth factors is stimulated,
• swelling is reduced,
• the antimicrobial activity of the organism itself, as well as of antibiotics, is enhanced.

The above are facts, scientifically based on numerous studies. Our two decades of experience confirm this.

Diabetic wounds

Diabetic foot is one of the most common complications of diabetes, accompanied by significant morbidity and mortality. Fifty percent of all lower limb amputations in the US are due to diabetes.

The main obstacle to successful wound healing in diabetics is the interruption of normal blood flow in the extremities with consequent hypoxia. Vascular insufficiency ranges from severe, multisegmental involvement of large vessels to mild changes in microvessels.

Despite a normal pulse and good blood supply to the large vessels, some diabetics have wounds that appear ischemic/hypoxic and that do not heal. In patients with obstructed large vessels, the mechanism of tissue damage is clear and proper healing can only be ensured by re-establishing blood flow.

When there are no changes in the large vessels, the mechanism of tissue damage is not so clear. Peripheral neuropathy (nerve tissue damage) exists in approximately 80% of diabetics with foot injuries. Associated mechanical trauma also plays a big role.

In patients with diabetes, there are also functional changes in the microcirculation that often cause a decrease in local blood flow and oxygen delivery to the tissues, which creates favorable conditions for the development of wounds.

It has also been proven that reduced skin blood flow is an independent risk factor, probably related to functional changes in the microcirculation. The polymicrobial nature of diabetic foot infections with a high rate of anaerobic microorganisms has also been well studied.

Infection increases foot ischemia by increasing the need (consumption) of oxygen in the tissue and reducing blood flow. Therefore, infection can overcome the marginal blood flow to the tissues, and sometimes can make even a good flow insufficient.

Treatment with HBO2 in the most extreme cases of ischemia is not of great benefit, but its effect in “marginally” blood-filled wounds can be very significant.

The increase in oxygen pressure in the wound achieved with HBO2 accelerates healing, strengthens antimicrobial defense mechanisms, and has a direct bacteriostatic effect on anaerobic organisms.

The goal of HBO2 treatment is to increase oxygen delivery to local ischemic tissues by various primary and secondary mechanisms with the aim of accelerating wound healing. The justification for the use of HBO2 in the treatment of diabetic foot infections has also been confirmed by prospective controlled clinical trials.

Topical (local) application of oxygen is not effective, and therefore has no role in the management of the diabetic foot. Hyperbaric oxygen treatment is very effective in the management of the compromised diabetic foot, significantly increasing the healing rate and drastically reducing the amputation rate.

Ulcers caused by the venous path

The mainstay of treatment of venous stasis ulcers is local wound care and external compression.

The usefulness of HBO2 in the treatment of non-diabetic patients with chronic leg ulcers was investigated in a double-blind, prospective, randomized study, and a 37.5% reduction in wound size was observed in HBO2-treated patients after 6 weeks, compared with a 2.7% reduction in the control group.

Surgical intervention is reserved for patients who have failed to respond to conservative treatment of these recurrent ulcerations. The role of hyperbaric oxygenation is justified only in selected patients in preparing the granulation layer above the debrided venous ulcer for possible skin grafting.

Pressure ulcers

The primary management of pressure ulcers is to change the patient's environment, diet, and aggressive wound care. Surgical treatment is often required, including excision of the ulcer and primary closure, grafting, or rotation of a skin flap.

HBO2 may sometimes be useful when osteomyelitis is present or to accelerate soft tissue healing or as a preparation for surgery or support for surgery.

Ulcers caused by arterial insufficiency

The primary treatment for persistent ischemic leg wounds is surgical revascularization. However, treatment with HBO2 may be beneficial, especially when the wound fails to heal despite maximal revascularization. Hyperbaric oxygen therapy may accelerate healing or prepare the vascular bed for skin grafting.

The importance of a multidisciplinary approach in treating problematic wounds

An aggressive multidisciplinary approach to the management of problematic wounds should be emphasized. Only under such conditions can HBO2 treatment provide a positive outcome and be a cost-effective treatment option.

In the treatment of problematic wounds, the most important thing is to identify the etiology and risk factors that hinder tissue recovery. For effective treatment, noninvasive vascular workup and transcutaneous oximetry should be performed to determine the degree of ischemia and hypoxia in the legs.

Correct prediction of wound healing is essential to avoid increased morbidity and mortality due to ischemia or failed debridement, amputation, and revascularization. In the past two decades, the standard method for noninvasive examination of ischemic extremities has been the ankle and local tissue systolic pressure index.

This method can be used in the diagnostic workup of problematic wounds to assess the possibility of soft tissue healing, determine the height of amputation, and select patients for HBO2. Based on the values measured by transcutaneous oximetry, it can be estimated whether HBO2 will be beneficial.

If tissue oxygen pressure can be increased in this way, wound healing is expected to be accelerated. If hyperoxygenated blood cannot be delivered to the affected tissue, HBO2 will not be effective. Critical ischemia in foot wounds therefore indicates arteriography and revascularization of the lower extremities.

Specific antimicrobial therapy plays an important role in treatment, as does optimal nutrition. Lack of protein in the diet increases prospective morbidity because it prevents healing and increases the rate of infections. In order to enhance immune function, metabolic control of hyperglycemia is necessary.

To achieve maximum blood flow and oxygen delivery to the tissues, an adequate blood volume is required. Aggressive daily wound care and meticulous dressing are prerequisites for new capillary budding, epithelialization, and prevention of infection.

Epithelialization usually occurs only when a capillary base is formed, but skin grafts are often required to accelerate wound closure. Long-term success also depends on prolonged monitoring of healing.

Factors that guide treatment decisions include the patient's rehabilitation potential, the ability and commitment of the surgical team, and the cost-benefit ratio of the measures to be taken.

Evaluating the usefulness of treating problematic wounds with HBOT

In the USA, 50,000-60,000 "major" amputations of the lower limbs are performed every year. Average mortality after amputation is 10%, and postoperative morbidity is not negligible either. Among the complications, the opening (dehiscence) of the wound, infection and revision of the amputation at a higher level stand out.

The rate of contralateral amputation is 10% per year. An aggressive and well-planned team approach saves more tissue and reduces morbidity and mortality.

Adjunctive treatment with HBO2, which is included early in hospital treatment as part of one such program, is highly cost-effective in helping to prevent amputations and subsequent complications. For the patient, amputation represents a significant disability that has major financial consequences.

The shortening of hospital treatment and the preservation of extremities greatly facilitate the return to everyday life and the workplace.