A Practical Guide To Understanding The Adjunctive Role Of HBOT In Wound Care
While the research behind the use of hyperbaric oxygen therapy (HBOT) for diabetic foot wounds goes back nearly three decades, many DPMs may not be aware of its benefits, how to access the treatment or how to become a supervising provider of HBOT.
First, let us review normal oxygen metabolism and cell function. Gas exchange occurs in the pulmonary alveoli where inhaled oxygen is diffused across the capillary membrane and carbon dioxide is released to be expired. Hemoglobin in the red blood cells (RBCs) has a higher affinity to oxygen at higher concentrations of oxygen. Thus, in the alveoli, with high concentrations of inhaled oxygen (the oxygen concentration of ambient air at sea level is 21 percent), hemoglobin offloads carbon dioxide and binds to oxygen. The circulatory system then carries the oxygen-saturated hemoglobin to the capillaries of various tissues (like the skin or subcutaneous tissue of a wound).
Molecular oxygen is required to create adenosine triphospshate (ATP) or energy in the mitochondria during aerobic cell respiration. After oxygen is used by the cells, tissue capillaries have low oxygen concentration and the carbon dioxide concentration is high. Hemoglobin then offloads the oxygen and binds to the carbon dioxide. The red blood cell circulates and returns to the lungs where the process repeats.
Hyperbaric oxygen therapy (HBOT) uses 100 percent oxygen at higher than normal atmospheric pressure to diffuse oxygen into the plasma.1 Concepts in physics help to explain this process. Henry’s law states that if you increase the pressure on a liquid, it increases the diffusion of a gas in the liquid.1 Think of a carbonated drink. Before you open a bottle of soda, you see no bubbles. The carbon dioxide (in this case) is diffused in the liquid under pressure. Once you unscrew the cap and release the pressure, the gas comes out of the liquid as bubbles.
In the case of HBOT, increasing the pressure in a chamber, usually two to three times the atmospheric pressure, or the equivalent pressure of being 33 to 66 feet underwater, will cause the oxygen to diffuse directly into the plasma and cross the capillary membranes where the tissue oxygen concentration is lower. Then it is available for cellular respiration. This drastically increases the partial pressure of oxygen in the tissue. Of course, oxygen is vital for normal cellular metabolism but the tissue hyperoxia from HBOT leads to angiogenesis, increased collagen production, improved osteoclast function and increased function of white blood cells (WBCs), helping to eliminate infection.1
Assessing Recent Studies On HBOT And Diabetic Foot Wounds
As a primary treatment, HBOT is only clinically indicated for a few non-podiatric-related conditions, such as carbon monoxide poisoning and decompression sickness.2 When it comes to podiatric-related conditions, one may use HBOT adjunctively for indications such as chronic refractory osteomyelitis, compromised skin grafts or flaps, and diabetic foot ulcers (Wagner grade 3 or higher).2
There have been mixed results for clinical studies of HBOT in the diabetic foot. One study of 94 patients found HBOT increased the likelihood of wound healing for people with Wagner grades 2,3 and 4 diabetic foot ulcers.3 A large retrospective analysis of Medicare data presented as an abstract by Lavery and colleagues matched 802 patients with diabetic foot ulcers and similar severity of disease who received HBOT with 802 patients who had advanced wound therapy (grafts, negative pressure wound therapy), and found a 33 percent reduced likelihood of amputation in the HBOT group.4
Another randomized controlled trial of 107 patients found that HBOT did not have any benefits over sham treatment in ulcer healing or prediction of amputation.5 However, this study’s amputation prediction endpoint was criticized since it was done by a blinded researcher evaluating patient photographs but many patients did not have an actual amputation.6
Accessing HBOT For Patients
Treating physicians provide HBOT to a patient in a single (monoplace) chamber or a large (multiplace) chamber. The use of monoplace chambers is most common and the attendant and supervising physician are outside the chamber. Many coastal hospitals have HBOT chambers with crews on 24-hour call for diving emergencies. Other hospitals also offer emergency HBOT services for carbon monoxide poisoning. However, the most common location of an HBOT program is within a hospital’s wound healing center. There are approximately 2,500 of these hospital-based programs nationwide.
Podiatrists wishing to access these programs for their patients should meet with the medical director to discuss the inclusion/exclusion criteria for patients and whether the DPM intends to continue treating the wound outside the hospital, limiting the patient’s hospital treatment to HBOT only. The Centers for Medicare and Medicaid Services (CMS) provides a list of approved conditions and requirements for HBOT coverage.2
Where Do Things Currently Stand With HBOT Privileging And Scope Of Practice Issues?
Podiatrists are ordering and supervising HBOT therapy in all but a handful of states. Most state laws governing the podiatry scope of practice are silent on HBOT just as they are silent on other methods of in-scope treatments. Instead, the laws are oriented to what structures are being treated, not how they are being treated. This gives podiatrists the legal scope to treat foot and ankle conditions by any means medical, surgical or physical. This would include the use of systemic antibiotics and other drugs by various routes of administration. In the case of HBOT, oxygen is the drug one is using to treat the foot or ankle condition, and it is administered by inhalation.
When administered in a hospital setting, HBOT is generally considered safe for foot and ankle conditions. However, because some rare complications of HBOT (including barotraumatic lesions and oxygen toxicity) could be life-threatening, most hospitals require physicians who supervise HBOT therapy to undergo a 40-hour HBOT safety course. These courses are offered by various organizations or one can commission a safety course on-site at a hospital.
For a comprehensive guide on the privileging of DPMs to supervise HBOT, please refer to an article I co-wrote for the Journal of the American Podiatric Medical Association in 2014.7 This includes sample delineation of privilege forms for the hospital that are free to use.
Final Thoughts
Limb salvage is a critical aspect of what podiatrists do on a daily basis. Staying informed as to the science, indications for and ways to access HBOT for applicable patients will add another dimension to the arsenal of treatments available for optimal wound care outcomes.
Dr. Rogers is the Medical Director of the Amputation Prevention Centers of America, a RestorixHealth company, which manages 230 wound and hyperbaric centers across 32 states. Dr. Rogers is also a member of the Board of Directors of the American Board of Podiatric Medicine (ABPM).
1. Choudhury R. Hypoxia and hyperbaric oxygen therapy: a review. Int J Gen Med. 2018;11:431-432.
2. Centers for Medicare and Medicaid Services. National coverage determination for hyperbaric oxygen therapy. Available at: https://www.cms.gov/medicare-coverage-database/details/ncd-details.aspx?NCDId=12&ncdver=3&DocID=20.29. Accessed October 10, 2019.
3. Löndahl M, Katzman P, Nilsson A, Hammarlund C. Hyperbaric oxygen therapy facilitates healing of chronic foot ulcers in patients with diabetes. Diabetes Care. 2010;33(5):998-1003.
4. Lavery LA, Rice JB, Desai U. Patients receiving hyperbaric oxygen (HBO) therapy have fewer major amputations than advanced wound care. Presented at Symposium on Advanced Wound Care (SAWC) Fall, November 1-4, 2018, Las Vegas, Nev.
5. Fedorko L, Bowen JM, Jones W, et al. Hyperbaric oxygen therapy does not reduce indications for amputation in patients with diabetes with nonhealing ulcers of the lower limb: a prospective, double-blind, randomized controlled clinical trial. Diabetes Care. 2016;39(3):392-399.
6. Mutluoglu M, Uzun G, Bennett M, Germonpré P, Smart D, Mathieu D. Poorly designed research does not help clarify the role of hyperbaric oxygen in the treatment of chronic diabetic foot ulcers. Diving Hyperb Med. 2016;46(3):133-134.
7. Rogers LC, DellaCorte MP, Stavosky JW, Millington JT, Capotorto JV. Credentialing guidelines for doctors of podiatric medicine supervising hyperbaric oxygen therapy a position paper. J Am Podiatr Med Assoc. 2015;105(4):367-370.
