Hyperbaric Oxygen Therapy Enhances Wound Healing Processes for Diabetic Wounds

Diabetic foot wounds are one of the major complications of diabetes and an excellent example of the type of complicated wound which can be treated with hyperbaric oxygen. It is well known that many diabetics suffer circulatory disorders that create inadequate levels of oxygen to support wound healing. Diabetic wounds present a major problem for modern health care. The foot is the most common site of infection in the diabetic. For diabetic patients, foot problems remain the number one reason for hospital admission. An estimated 25% of Canadians with diabetes develop foot problems, and one in 15 require a limb amputation during their lifetime.

Oxygen is one of the most versatile and powerful agents available to the modern medical practitioner today.The therapeutic use of oxygen under pressure is known as hyperbaric oxygen therapy (HBOT) and has been used to assist wound healing for almost 40 years. HBOT has several specific biological actions which can enhance wound healing processes:

* Oxygen used under pressure of hyperbaric oxygen can assist wound healing.
* HBOT is considered unnecessary simple, well-perfused wounds, but can be used successfully in hypoxic or ischemic wounds such as diabetic wounds, venous stasis ulcers, failing grafts and flaps, necrotising soft tissue infections and refractory osteomyelitis.
* In wound healing, hypoxia is an insufficient supply of oxygen which prevents normal healing processes. HBOT provides the oxygen needed to stimulate and support wound healing.
* HBOT is able to combat clinical infection such as gas gangrene by acting directly on anaerobic bacteria, enhancing leukocyte and macrophage activity and potentiating the effects of antibiotics.
* HBOT is a safe non-invasive, non-toxic therapy.

Hypoxia (lack of oxygen) can be defined as an insufficient supply of oxygen to allow the healing process to proceed at a normal rate. In a typical wound care treatment, hyperbaric oxygen is capable of providing tissue oxygen levels of greater than 11 times normal values. Most chronic wounds are hypoxic and HBO provides the oxygen needed to stimulate and support wound healing.

When used in wound healing HBO provides a short pulse of oxygen - typically 90 minutes in a 24 hour day. HBO acts in numerous ways that affect the wound after the treatment has stopped. There are eight principal methods in which HBO is capable of affecting tissue:

* Pressure effects of oxygen
* Vasoconstrictive effects of oxygen.
* 100% oxygen concentration effects on the diffusion gradient.
* Hyperoxygenation of ischemic tissue.
* Down regulation of inflammatory cytokines.
* Up-regulation of growth factors.
* Leukocyte effects.
* Antibacterial effects.

Hbo has six actions which have been used to combat clinical infection:

1. Tissue rendered hypoxic by infection is supported by oxygen.
2. Neutrophils are activated and rendered more efficient.
3. Machrophage activity is enhanced.
4. Bacterial growth is inhibited.
5. The effect of antibiotics is potentiated.

Support of infected hypoxic tissue: Soft tissue and bone infections are frequently accompanied by localized areas of tissue hypoxia caused by the inflammatory processes accompanying infection and by subsequent vascular thrombosis. As the infected tissue becomes infiltrated with inflammatory cells the oxygen level falls. Anaerobic bacteria are particularly susceptible to increased concentrations of oxygen.

In properly selected patients the success rate is high and there are few absolute contraindications. Transcutaneous oxygen levels and doppler testing can help to predict results. HBOT in properly selected cases, has been effective in preventing amputations, speed up healing of chronic ulcers and fistulae, saving threatened skin flaps and permitted surgery that would not have been possible without it. This in turn results in improved quality of life for patients.

The incidence of amputation in diabetics remains unacceptably high: 6 per 1,000 patients. Diabetics account for 50 - 70 percent of all amputations performed each year. In 1986, 152,000 amputations were done in America. Ten percent of those surgeries resulted in the loss of a foot, 35% involved the loss of a lower leg, and 30% resulted in the loss of the knee joint. Ipsilateral or higher amputation occurs in 24% of cases. One complication often does unrecognized: contralateral amputation, which occurs at a rate of 10% per year.

Diabetic amputees also experience other difficulties. Only 50% of the patients survive more than 3 years after the amputation (USA survey data). Although many individuals who lose limbs traumatically can expect to be rehabilitated to full activity, only 40 - 50% of elderly amputees can not expect to enjoy such a successful outcome. The duration of hospitalization for treatment of diabetic foot infections averages 22-36 days.

Amputation offers a poor solution. Patients pay high personal costs when limbs are lost. When an amputation occurs, patients generally remain hospitalized for 40 days and to maximize walking ability or potential, patients may need an additional 6-9 months of rehabilitation. Many elderly diabetic amputees remain bound to wheelchairs for the rest of their lives because they lack sufficient energy, balance, and strength to walk. Their sedentary existences lead to other health problems. Within 2 years, for example most amputees must undergo stump modification or proximal reamputation.

Then there are the social costs of amputation to consider. Many amputees fail to maintain productive lives because they can no longer sustain gainful employment. But personal costs perhaps loom the largest in decreasing a patient's quality of life.

Three factors predispose a diabetic to develop wound problems: neuropathy, angiopathy and immunopathy. Neuropathies involving both peripheral (motor and sensory fibers) and autonomic innervation are common complications of long-standing diabetes mellitus. Such pathology often involves a combination of these fibers. Among the most commonly recognized neuropathies is sensory neuropathy, perhaps because of its clear pathophysiology and the ease in evaluating the conditions. This neuropathy contributes to the possibilities of patients becoming infected. When patients fail to feel pain and proprioceptive sensation, they injure themselves more easily and often fail to rapidly recognize tissue damage and infection. Patients experiencing such problems can also repeatedly traumatize the joints and tissue of the foot, creating increasingly serious problems.

Motor neuropathy causes weakness of various muscle groups, ultimately resulting in foot deformities. Typically, weakness of the intrinsic muscles lead to protrusion of the metatarsophalangeal joints. Such a condition eventually causes hammer toes and pes cavus because the weight bearing surfaces are structurally overloaded. Destruction of callus, skin breakdown and trophic ulcerations may also develop.

Such events open the first line of defence against infection and offer a fertile breeding ground for invasive bacteria. Autonomic dysfunction leads to decreased sweating. Resulting dryness may predispose the patient to more scaling, cracking, and fissuring of the skin of the foot. With each crack, further tissue breakdown and infection can occur.

Angiopathy, or the presence of peripheral vascular disease affecting the foot. contributes to the possibility of infection. Two disease processes may be involved, although the mechanisms are not yet clear. Microangiopathy and chronic macroangiopathic occlusive arterial disease contribute to vascular problems. The recent medical literature challenges the importance of microvascular versus macrovascular changes. Now researchers suspect microangiopathy may relate to inhibition of diapedesis of leukocytes and exchange on immune substance through thickened capillary basement membranes. Similarly, oxygen diffusion through thick membranes is reduced. Prospective controlled studies have substantiated the thickening of capillary basement membranes, a microvascular change clinicians had postulated.

But perhaps more importantly, diabetics experience the effects of macroscopic obstructive arterial disease. Such disease can lead to diminished flow through major arterial systems. The development of collateral circulation may maintain an adequate blood supply at ambient

temperatures. Vascular reserve is often diminished, however. One prospective study identified vascular impairment as one of three factors significantly more common in diabetics with foot lesions. Doppler studies were used to assess the impairment.

Another important pathophysiologic factor involves changes in the immune system of the diabetic patient, when hyperglycemia occurs. Migration of polymorphonuclear leukocytes, phagocytosis and cell-mediated immune response are all impaired in the poorly-controlled diabetic.

Once an infection occurs, most tight glucose control is lost. Data analyzed in two recent reviews suggest that patients with diabetes mellitus are predisposed to more frequent and severe infections. They are also less capable of fighting those infections.

HBOT offers physiological benefits for such patients. They include: improved oxygenation of threatened margins of wounds, generation of granulation tissue, enhanced phagocytosis and killing of select organisms. Still other benefits are enhanced penetration of some organisms by antibiotics whose transmembrane transport is oxygen dependent, and improved wound healing with an increased rate of fibroblast collagen production to support capillary angiogenesis. HBOT offers beneficial direct bacteriostatic effect on anaerobic micro-organisms.

HBOT is an adjunctive therapy, which in combination with other disciplines involving treatment, will provide a powerful tool for the treating physician.