Hyperbaric Oxygen Therapy Indications Simplified

Indication #4: Compromised Skin Grafts and Flaps

Skin grafting is a procedure in which a surgeon takes skin and applies it over the wound with the intention of healing/closing it. Skin grafts can be variable in shape and size and may be used in the setting of burns, ulcers, surgical dehiscence, and many other wounds. Skin grafting dates to over 3,000 years ago, originating in India.¹  

There are several types of skin grafts. The first is what we know as an autograft or autologous skin grafting, in which skin from the patient’s own donor site is harvested and used. Due to the nature of these grafts, they typically stay in place and incorporate nicely into the wound if the wound bed is vascularized. There is no need of reapplying the graft or removing the graft. We simply allow and encourage the graft to mature or “take” by providing the optimal conditions for wound healing and epithelialization.

Among autografts, the most used are full-thickness and split-thickness skin grafts (STSG). The difference between these two lies in the skin layers included while harvesting the graft. In a full-thickness skin graft the physician harvests the entire layer of skin including the dermis and epidermis, which then typically creates a secondary wound that will need to be closed, most often, with a primary approach.² Meanwhile, in an STSG, the epidermis and only part of the dermis are harvested, which will allow the donor site to heal without further flaps or closures. STSGs are typically meshed with a device at the time of harvesting. This process allows the skin to expand farther and cover a larger surface area. It also allows for proper drainage of exudate, which will further contribute to healing.

Allografts are skin taken from another person. These will typically need to be removed from the wound at some point, as there is no antigenic compatibility with the recipient and will undergo an apoptotic process. Often, multiple allografts will need to be applied prior to achieving full closure of the wound and these are used as a sort of scaffold for new tissue to fill in the wound. It is not unusual for clinicians to use allografts to prepare the wound bed for an autograft.

Xenografts are skin harvested from other species such as fish, pigs, or sheep, to name a few. The wound care industry is booming with options in this field. Usually, xenografts serve as a temporary skin substitute and aid with wound bed preparation for a few weeks, prior to proceeding with an autologous skin graft. Finally, we have synthetic skin substitutes, which are products that are manufactured to function as skin.^3,4 For the purposes of this article, we will refer to autografts as skin and tissue flaps.

Skin and Tissue Flaps

Skin/tissue flaps are a construct of skin and underlying subcutaneous tissue that maintain their own mostly intact vascular supply, which is then repositioned or relocated from a donor site to a recipient site (primary defect). The nomenclature or categorization of tissue flaps can be done in different ways. One of the most popular ways of categorizing them is via blood supply, with random, axial, pedicle and perforator flaps being the most common.⁵ Another categorization is by tissue type, which divides flaps into cutaneous, fasciocutaneous, musculocutaneous, or muscle flaps. Additionally, flaps can be subdivided into advancement, rotational and transpositional flaps. These subtypes are simply describing the direction in which the surgeon is moving the skin to cover the defect.

Different flaps are better suited for different primary defects. The viability of a skin flap is highly dependent on the quality of blood flow/perfusion. If the blood supply is compromised, the flap will suffer ischemia and even necrosis.

Incidence of Skin Graft and Tissue Flap Failure

Over the years, the success rate for both skin grafts and tissue flaps has increased markedly. However, there are still grafts and flaps that fail to take and become ischemic or necrotic. It is difficult to provide the reader with a definite incidence rate of failure as each is dependent on the type of graft/flap, its inherent properties, the comorbidities present, and the unique situation of the patient. Comorbidities that interfere with healing and may be responsible for skin graft/flap failure are radiation injury, chemotherapeutic agents, immunosuppressive medications, peripheral vascular disease, diabetes, and autoimmune conditions, to name a few. The location of the graft/flap is also an important risk factor to consider.

Reddy and colleagues report that lower limb grafts have high failure rates.⁶ Regarding tissue flap failure, some sources report overall tissue flap failure to be over 5%, with certain anatomical locations having higher failure rates.⁷

Clinical evaluation of grafts and flaps should include:

1. Review of the color of flap/graft
2. Capillary refill
3. Temperature as described on the Table to determine if graft is compromised because of arterial flow, venous congestion or random ischemia.

HBOT and Compromised Grafts/Flaps

Referral to the wound care center is indicated for patients with compromised skin grafts and tissue flaps. They should be referred to a wound care clinician for consideration for hyperbaric oxygen therapy (HBOT) at the first signs of skin graft failure or tissue flap necrosis in order to improve outcomes and increased chances of flap salvage. The likely underlying pathology is tissue hypoperfusion/hypoxia. The mechanism of HBOT in the setting of this indication is targeted at the underlying pathophysiology, therefore, there is no need to treat patients for the support of normal, uncompromised grafts of flaps.

Hyperbaric oxygen therapy has several effects that are beneficial for healing compromised grafts. These effects are closely related to the enhancement of fibroblasts, collagen synthesis, and increased rate of neo-angiogenesis that occur with HBOT, leading to increased blood supply, increased oxygen delivery to hypoxic tissues, and an overall decrease in edema. This is highlighted in cases in which the grafts are in areas that have experienced trauma that can lead to large amounts of edema such as crush injuries, degloving injuries and burns. Additionally, HBOT can help lower infection rates through oxygen’s bactericidal and bacteriostatic effects.⁹

The HBO treatments are given at a pressure of 2.0–2.5 ATA for 90–120 minutes. Mechanical causes of flap compromise that can be treated surgically should be addressed prior to initiation of HBO therapy. HBO therapy should be started as soon as signs of flap or graft compromise appear. Flap viability can be assessed by clinical judgment as well as other noninvasive techniques like transcutaneous oximetry and near infrared spectroscopy.

Failed grafts/flaps are extremely expensive with increase morbidity. Adjunctive HBO therapy can decrease financial, physical, and mental cost by salvaging compromised grafts/flaps by minimizing the need for secondary surgeries and alternate donor sites.¹⁰

Word to the Wise

• Do not use HBOT for non-compromised skin graft and tissue flaps. Identification of the underlying cause for graft or flap compromise is important in determining the proper clinical management and use of HBO therapy.
• Always correct the mechanical cause of decreased flap perfusion before recommending HBOT for compromised flap.
• Sometimes the indication for HBO therapy may be better classified by the underlying cause of wound healing compromise (ie, soft tissue radionecrosis, osteoradionecrosis, chronic osteomyelitis, diabetic foot ulcer)
• HBOT is only indicated for compromised autografts and skin flaps—and not indicated for xenografts and allografts—compromise or failure.

Denise Nemeth is a second-year medical student at the University of the Incarnate Word School of Osteopathic Medicine in San Antonio, TX. Formerly a general and vascular surgery PA in a rural community, Ms. Nemeth aspires to become a general surgeon. She is certified wound specialist with the American Board of Wound Management. Her interests include rural health, wound healing, colorectal surgery, and minimally invasive surgery.  

Jayesh B. Shah is Immediate Past President of the American College of Hyperbaric Medicine and serves as medical director for two wound centers based in San Antonio, TX. In addition, he is president of South Texas Wound Associates, San Antonio. He is also the past president of both the American Association of Physicians of Indian Origin and the Bexar County Medical Society and Current of Board of Trustees of Texas Medical Association.   

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References
 
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7. Kwok AC, Agarwal JP. An analysis of free flap failure using the ACS NSQIP database. does flap site and flap type matter? Microsurgery. 2017;37(6):531-538. doi: 10.1002/micr.30121.
8. Jones MW, Cooper JS. hyperbaric therapy for skin grafts and flaps. [updated 2022 oct 24]. in: StatPearls [internet]. treasure island (FL): StatPearls publishing; 2022 jan-. available from: Https://Www.ncbi.nlm.nih.gov/books/NBK470219/ . .
9. Phillips JC. Understanding hyperbaric oxygen therapy and its use in the treatment of compromised skin grafts and flaps. Plast Surg Nurs. 2005;25(2):72-2. doi: 10.1097/00006527-200504000-00006.
10. Kleban S, Baynosa R. The effects of hyperbaric oxygen on compromised grafts and flaps, Chapter 5. In Moon MD, UHMS Hyperbaric Oxygen Therapy Indications, 14th Edition, 2019.