Dr. Stone serves as Medical Director for the hyperbaric medicine unit at the Institute for Exercise & Environmental Medicine. He received his medical degree from the College of Osteopathic Medicine of the Pacific and received a master of public health degree from Harvard University.
What are some of the particular challenges of treating Diabetic Foot Ulcers?
I think if you talk about diabetes one of the biggest problems we find is that half of the folks who have diabetes don’t know they have the disease. So if you look at the national population there are 16 million Americans with diabetes, and eight million of them are unaware of their illness. Here in Texas, we estimate there are about a million individuals with diabetes and again, half of these folks don’t know they have the disease.
When we have patients present to the wound care center with chronic non-healing wounds one of the first things we do is test them for diabetes. Many times we are the first physicians to diagnose their illness. Patients that come for treatment of a wound discover that their underlying problem is a chronic disease with multisystem effects that will require lifetime treatment.
With diabetes, about eighty percent of patients will have some form of neuropathy. There are three different types of neuropathy; sensory, motor, and autonomic. Patients can develop one form or a combination of the different neuropathies. It is believed that lack of glucose control contributes to the development of neuropathy in diabetic patients. Again, since half of diabetic patients are unaware of their disease for years, many patients present with advanced cases of neuropathy. We find that as a result of the effects of neuropathy the patient presents to the clinic not realizing the true extent of their problem.
Sensory neuropathy causes a loss of sensation. It can begin slowly and progress to a total loss of protective sensation (LOPS) for the person with diabetes. Many people don’t realize that they have developed a loss of sensation until we perform a Semmes-Weinstein Monofilament test on their feet. By pressing the monofilament against their feet, while their eyes are closed, we can exert a precise amount of pressure on the foot. Initially, some patients may have a delayed response to the sensation progressing to no response at all to the monofilament pressure. The loss of sensation in the diabetic foot puts patients at increased risk for trauma to their feet. A rock in the shoe of a diabetic patient with sensory neuropathy may go unnoticed for days and cause extensive damage resulting in an infected wound. This wound may ultimately progress to an amputation. Dangers for the patient with LOPS range from foot damage from ill fitting shoes, burns from hot bath water, to unnoticed foreign objects imbedded in the foot.
Motor neuropathy results in damage to the nerves that control the muscles of the foot. The nerve damage in turn can cause atrophy (wasting away) of the muscle that results in deformities of the foot and toes. The toes pull back and up resulting in what is commonly called “hammer toes”. It also causes the fat pad on the bottom of the foot, which acts as a cushion for the bones of the foot, to shift up resulting in callous formation and wounds. The muscle atrophy causes foot deformities that in turn leads to altered weight bearing.
Autonomic neuropathy causes damage to the nerves that control the diameter of the blood vessels and the sweat glands in the foot. Loss of the sweat glands leads to abnormally dry and cracked skin. Cracks in the skin puts the patient at an increased risk for infection, while dry skin causes itching and an increased risk for trauma from scratching. Loss of control of the diameter of the blood vessels in the foot ultimately results in a loss of bone minerals leading to a collapse of the bones in the foot. The foot deformity is called Charcot foot. It is sometimes referred to as “rocker-bottom” foot because of its appearance caused by the collapse of the arch of the foot.
Wound healing is a complex process that necessitates a multi-disciplinary approach to patient care. Wound care specialists work in conjunction with vascular surgeons, plastic surgeons, orthopedic surgeons, registered dietitians, diabetic educators, physical therapists, orthotists, and specialized wound care nurses to deliver customized patient care. Patient education is key. We don’t want to just heal patients; we want to keep them healed.
What is Hyperbaric Oxygen Therapy?
Hyperbaric oxygen therapy (HBOT) is the process whereby the patient breathes 100% oxygen in a room or chamber that is pressurized at a level greater than sea level (sea level represents one atmosphere absolute). It is a systemic therapy in which increased levels of oxygen are absorbed through the lungs. It is not a topical therapy. HBOT increases the amount of dissolved oxygen in the blood plasma which in turn delivers increased concentrations of oxygen to all areas of the body perfused by blood plasma.
What is the medical use for Hyperbaric Oxygen Therapy?
The Undersea and Hyperbaric Society approved the use HBOT as a primary treatment for three conditions: air or gas embolism, decompression sickness, and carbon monoxide poisoning. It also approved it as a secondary form of treatment for the following conditions: radiation tissue damage (soft tissue and osteoradionecrosis), gas gangrene, compromised skin grafts and flaps, necrotizing soft tissue infections (subcutaneous, muscle, fascia), crush injury, compartmental syndrome, acute traumatic ischemias, chronic refractory osteomyelitis, and problem non-healing wounds.
Why does it work for wound healing?
HBOT works in wound healing by allowing the increased concentrations of oxygen in the plasma to circulate and oxygenate wounds that are hypoxic. It also increases the distance that oxygen molecules can diffuse from the vessels into the tissues. Research has demonstrated it causes vasoconstriction (reducing edema), increases collagen synthesis and the formation of new blood vessels, and enhances leukocyte function (fighting infection). We know for fibroblast proliferation (a building block of new tissue) you need to have at least fifteen millimeters of oxygen tension. In some hypoxic wound environments this minimal level of oxygen tension does not occur. Certainly the key to wound healing in the patient with a large vessel occlusion is to be revascularized. HBOT is enhanced if the vascular pathway to the wound is open and efficient.
Diabetic wound patients often have great difficulty healing their wounds. We have to look at the total picture of wound healing: is there an infection, is the wound off-loaded, is there exposed bone, is the dressing correct, debridement, patient compliance, glycemic control, and revascularization of occluded vessels. I always stress the importance of revascularization if it is appropriate or possible. There is a subset of patients, whom even after revascularization of their blood vessels, that fail to improve. These patients have microangiopathic (small vessel disease) problems with their circulation. We screen these patients to see if breathing increased levels of oxygen increases the concentration of oxygen at the tissue level near the wound (Transcutaneous Pressure Oximetry). If tests results indicate increased oxygen levels, the patient may certainly benefit from HBOT.
Do you consider hyperbarics for other wounds, such as venous leg ulcers?
Well, not really. The underlying problem for venous leg ulcers is usually not inadequate levels of oxygen. The pathology responsible for venous leg ulcers is venous congestion and elevated pressures in the venous system. The key treatment for venous leg ulcers is adequate debridement, infection and excessive drainage control, compression therapy and manual lymph drainage.
You received an American Diabetes Association grant to study hyperbarics in wound therapy. Do you believe hyperbarics may emerge as the standard of care for advanced wounds?
I think that for certain hypoxic wounds, hyperbaric therapy is very appropriate. I think there is a wealth of data to support the use of HBOT for wound healing. In April of 1999 the ADA developed a consensus statement on the diabetic foot stating that HBOT was beneficial as an adjunctive therapy in certain diabetic ischemic wounds.
Hyperbarics have been around for 40 years. Are there other unexplored modalities?
I think so. Growth factor therapy and bioengineered dressings are both emerging therapies. I think we are in the infancy of advanced wound care. Research scientists are still discovering the intricate sequence of events necessary for acute and chronic wound healing. It is an exciting field.
I also noticed that some of your research focuses on the nutritional aspect of wound healing. How does diet affect wound healing?
Early aggressive nutritional intervention is essential to promote wound healing. Despite optimal wound care, healing is greatly compromised if the patient is malnourished. Statistics have shown that as many as 85% of nursing home patients are considered malnourished. The problem that arises with these types of wound patients is two-fold. They are malnourished, and because of their wound, they are also catabolic. During the catabolic phases of illnesses, the body will utilize protein for energy. It gets this protein from lean tissue or what is known as metabolically active tissue. This includes muscles, organs and visceral proteins. This is a highly inefficient means of energy production and if the phase is prolonged, wound healing will cease and death will result. The human body does not store excessive protein as we do fat. Therefore, any loss of protein is considered life threatening.
So is protein one of the critical nutrients required for healing?
I think so. Again, our protein reservoir is limited. We know that wound healing is greatly diminished if 20% of our lean tissue has been catabolized. This type of catabolism, or breakdown, can occur rather quickly. However, it may take up to twenty times as long to rebuild the loss. Until the body has regained 50% of the lost lean tissue, wound healing will not occur. This may take years. Therefore it is important to minimize losses from the very beginning. One of the tools I have found successful in expediting the reversal of involuntary weight loss is the use of anabolic steroids.
Practically how can a caregiver or patient determine whether they are receiving adequate nourishment? Is weight a proper gauge of nutrition?
Weight is only one of several tools that can be used to assess the adequacy of nutrition support. Unfortunately in stressed or catabolic patients, weight is useless. Secondary to hydration status, weight may remain stable and mask the severity of the lean tissue losses. An overweight patient may actually be over fat and remember protein is what is being degredaded for energy. Therefore, it is a fallacy that an obese patient, after major trauma doesn’t need to be fed. Thus, weight in these types of over weight or obese patients are useless. There are labs that may be used as indicators for nutritional status as well as assessing accuracy of nutritional regimens. They include visceral proteins such as transferrin, albumin and pre-albumin. Nitrogen balance studies are also useful, however 24-hour urine collection is sometimes hard collect. Some facilities have metabolic carts that are used to determine, with much accuracy, the patients’ energy needs as well as determine what substrate is being utilized for energy production. Although these are standard types of tests, they do require much interpretation and understanding of the metabolic abnormalities associated with catabolism. That is why it is essential to include the dietitian in the overall nutritional care plan for these patients.
Do you have any final thoughts about wound care?
What we know is that a multidisciplinary approach is key. In our practice, it’s the nurses, the dieticians, the physical and occupational therapists, surgeons and other specialists—that are all key components working as a team to get wounds to heal. It needs to be a group effort.
For more information on Dr. Stone's clinic and research into hyperbaric oxygen therapy, please visit:Wound.com