Chronic wounds have low tissue perfusion and oxygenation which means that they can benefit from increased delivery of oxygen. Hyperbaric oxygen therapy is being used in wound care facilities to improve tissue oxygenation and wound healing.  Around 500 facilities in the United States provide hyperbaric oxygen therapy (HBOT) in either single occupant or multiplace chambers. It has emerged as a viable treatment option for chronic, non-healing wounds when traditional methods fail to show any improvement. [1] Wound care specialists and podiatrists should familiarize themselves with the indications and usage of hyperbaric oxygen therapy (HBOT) for wound healing. 

What Is Hyperbaric Oxygen Therapy?

Hyperbaric Oxygen Therapy (HBOT) is a technique of delivering oxygen under high atmospheric pressure to tissues in specially designed chambers. Under high atmospheric pressure, oxygen functions as a pharmacological agent and can be used for therapeutic purposes. [2] Currently, it is being used as an adjunctive treatment for several conditions like decompression sickness, carbon monoxide poisoning, radiation injury, and chronic, non-healing wounds. 

The person is placed in a pressurized chamber with 100% oxygen. The chambers can either be “multiplace” (multiple patients) or “monoplace” (space for a single occupant). Multiplace chambers are better suited for severely ill patients and use a mask for the delivery of oxygen. Monoplace chambers on the other hand are more suitable for stable, chronic patients. They do not require the use of a face mask as they are directly pressurized using oxygen. [3] Hyperbaric oxygen therapy is usually given for 60-90 mins at a pressure of 2 to 3 ATA. Pressures that exceed this limit pose a risk of oxygen toxicity. [4]

How Hyperbaric Oxygen Therapy Affects Wound Healing

The amount of oxygen dissolved in the blood significantly increases under high atmospheric pressure. As tissue hypoxia is a key factor contributing to wound chronicity, hyperbaric oxygen therapy has the potential to improve tissue oxygenation and hence wound healing. Despite the sparsity of conclusive evidence in favor of its routine use, hyperbaric oxygen therapy has been demonstrated to have a positive effect on wound healing in several studies. [5] Hyperbaric oxygen therapy affects the wound healing process through the following mechanisms:

• Increased Tissue Perfusion: The amount of gas dissolved in a liquid medium is directly proportional to the partial pressure of the gas, according to Henry’s law. Therefore, a greater amount of oxygen is dissolved in blood under a high atmospheric pressure which is subsequently delivered to the tissues. [6] As a result of hyperoxygenation, the hypoxia in chronic wounds is reversed which helps to accelerate wound healing.
• Reduced Local Edema: Oxygen has a vasoconstrictive effect on both arteries and veins. This helps to reduce edema and congestion, and also improves oxygen delivery to hypoxic tissues. [7]
• Improved Metabolism: The increase in partial pressure of oxygen accelerates wound healing through enhanced collagen synthesis, fibroblast proliferation, and angiogenesis. It also helps to improve reepithelialization in a chronic wound. [8]
• Bactericidal Action: Neutrophils require oxygen for optimal bactericidal activity. Patients are susceptible to infections when oxygen levels fall due to reduced bactericidal action of polymorphonuclear neutrophils. Through an increase in available oxygen, hyperbaric oxygen therapy enhances the bactericidal activity of leukocytes against aerobic gram-negative and gram-positive bacteria. In addition, it is also effective against anaerobic organisms through its cytotoxic effect. [9]
• Upregulation of Growth Factors: Hyperbaric oxygen therapy (HBOT) has been found to improve the upregulation of cytokines including platelet-derived growth factors. As PDGF is involved in angiogenesis, hyperbaric oxygen therapy can help improve neovascularization in chronic, non-healing wounds. [10]

Indication For Hyperbaric Oxygen Therapy In Wound Care

The majority of research that studied the effect of hyperbaric oxygen therapy on wound healing focused on diabetic foot ulcers. The etiology of lower extremity diabetic ulcers is multifactorial, and hyperbaric oxygen therapy can address several of these factors to improve wound healing. Hyperbaric oxygen therapy has been found to reduce the rate of amputation in patients with diabetic foot ulcers and therefore is now being advocated for the treatment of diabetic ulcers. [11]

Hyperbaric oxygen therapy can also be beneficial in the treatment of patients with extensive soft tissue injury. A trial studying the application of hyperbaric oxygen therapy in patients with crush injury found significantly improved healing rates. It has also been found to improve the survival rates of skin grafts and flaps. [12]

Therefore, hyperbaric oxygen therapy can be indicated by podiatrists and wound care specialists for wounds that are not amenable to conventional treatment. As with other treatment modalities, patients and host factors should be simultaneously addressed through a comprehensive wound care plan for optimal results.

References:

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2. Gottrup F, Firmin R, Hunt TE, Mathes SJ. The dynamic properties of tissue oxygen in healing flaps. Surgery. 1984 May 1;95(5):527-36.
3. Bhutani S, Vishwanath G. Hyperbaric oxygen and wound healing. Indian Journal of Plastic Surgery. 2012 May;45(02):316-24.
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12. Perrins DJ. Influence of hyperbaric oxygen on the survival of split skin grafts. The Lancet. 1967 Apr 22;289(7495):868-71.