There are many reasons why wounds fail to heal. Some wounds, especially chronic ones, are hypoxic, meaning they lack oxygen. Therefore, hyperbaric oxygen therapy (HBOT) can be used to re-oxygenate wounds and help them heal. Two researchers--one who treats humans and another who treats horses--described their experiences with HBOT on June 2 at the American College of Veterinary Internal Medicine Forum in Louisville, Ky.

Hyperbaric oxygen therapy involves increasing the amount of oxygen dissolved in the blood by breathing in oxygen under pressure. The patient must be placed in a chamber that can be pressurized. Different oxygen dosages and protocols are recommended for different conditions that are treated with hyperbaric medicine.

Paul J. Sheffield, PhD, CAsP, CHT, of San Antonio, Texas, senior editor of Wound Care Practice, described how scientists measure oxygenation of tissues in humans using oxygen electrodes. Many of the studies are based on diabetic wounds that sometimes result in amputation. To predict a wound's response to traditional treatments, Sheffield measures the oxygen level of the wound with transcutaneous (on the skin) oxygen sensors in a process called transcutaneous oximetry. These sensors are non-invasive and measure the arterial oxygenation of the capillary bed beneath the sensor.

"Moderate to severely hypoxic wounds are unlikely to heal unless supplemental oxygen is provided to the patient," Sheffield said. "Most wounds don't need added oxygen," he said, "But for those that need oxygen, HBOT is valuable treatment to activate the healing cells. after one hour of hyperbaric oxygen therapy (when the patient is breathing the oxygen and the wound is being exposed to it, as would occur in an HBOT chamber), the plasma has about 15-20 times more oxygen than normal.  When the treatment is over  tissue oxygen remains elevated for about three hours," which can be very beneficial to moderate and severely hypoxic wounds.

"Assessment of tissue oxygenation is a valuable tool in medical decision-making to help determine the best local wound treatment option, predict successful amputation sites (in humans), select candidates for hyperbaric oxygen therapy, and predict non-responders to treatment," Sheffield summarized.

Equine HBOT
Nathan Slovis, DVM, Dipl. ACVIM, CHT, of Hagyard Equine Medical Center in Lexington, Ky., has been using HBOT in equine patients since 2003.

He listed 15 therapeutic effects of HBOT. These ranged from reversal of hypoxia ("dummy foals") to stimulation of capillaries to re-establish in damaged areas of tissue, and from modulating immune system responses to accelerating collagen deposition (tendon healing).

Slovis described the successful HBOT treatment of several severe wounds, including a traumatic, necrotic (tissue had begun dying) hock wound that had developed granulation tissue, a knee injury with exposed joint spaces, and a burn victim.

Slovis' highest-profile HBOT case was a Saddlebred that had been attacked along with four others in 2003 with an injection of a caustic substance in one pastern. Three of the horses' wounds deteriorated to the point where they were euthanatized because of the severe necrosis or developing contralimb laminitis (caused by the "good" limb bearing too much weight). Cats Don't Dance spent several weeks at Hagyard, where Slovis treated the horse with HBOT and other therapies. Slovis showed the progression of Cats' wound healing with photographs.

"This is an adjunct therapy," Slovis emphasized, cautioning against pegging the treatment as a cure-all. "You don't just use it by itself."

Hagyard has established treatment protocols for septic arthritis, osteomyelitis, tendon or suspensory ligament injury, post-colic surgery or prevention of ischemic reperfusion injury (when blood returns to an area that's been deprived by blood), exercise-induced pulmonary hemorrhage (bleeders), and perinatal asphyxia syndrome ("dummy" foals).

"Bottom line, we're just getting started studying this," Slovis said. "Be cautious, this is not for everything, we still need more scientific studies."

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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