Oxygen Therapy for Horses

Hyperbaric oxygen therapy (HBOT) might be most easily recognized as the technology used to treat the "bends" or decompression sickness in divers. Its use as a medical treatment for humans is not new, but has undergone a resurgence in recent years. Many medical schools now have hyperbaric centers, and there is a list of Medicare-approved conditions for which HBOT is considered appropriate.

How does HBOT work? It involves increasing the amount of oxygen dissolved in the blood by breathing in oxygen under pressure. This is accomplished by the patient being placed in a chamber that can be pressurized. For humans, this can be a single-person or multi-person chamber. Oxygen is considered a drug, and appropriate dosages and protocols are recommended for different conditions.

The first point for consideration is that HBOT might help salvage injured tissue. If injured tissue can be salvaged, much of the recovery time can be shortened and functional tissue might be saved that would ordinarily be lost. With injury, many times some amount of tissue will lose enough blood supply to die and slough, and the process of wound healing is prolonged by the time required for the body to "clean up" this dead tissue and heal by scar formation. This same issue occurs in bone infections where the body may have to reabsorb dead bone before healing can occur.

The second area where HBOT is showing effectiveness is on the body's infection-fighting capabilities. HBOT has been shown to enhance white blood cells' ability to kill bacteria, and it also may enhance the activity of certain antibiotics. These actions, acting in concert, might provide the body with added benefit in fighting infections in a variety of tissues.

One of the effects of HBOT is a marked increase in the amount of dissolved oxygen in the plasma. This increased concentration of oxygen does a couple of things. First, it allows the oxygen to diffuse further out into the tissues, which is very important in tissue injury where the distance from the blood vessels to the cells in the body may be increased by tissue edema (fluid buildup that causes swelling with injuries). Second, it causes constriction of small blood vessels, which helps decrease the formation of edema.

Wounds are among the most common conditions of humans that are treated with HBOT, but bone infections and injuries to the brain or spinal cord are also being treated. Like many advances in veterinary medicine, new technology or medical treatments follow progress in human medicine. We are in the very early stages of application of hyperbaric oxygen therapy to medical problems of the horse. Many of the same HBOT-treatable medical conditions of humans also occur in the horse. Wounds and a variety of traumatic injuries are extremely common in the horse (as most horse owners are aware!). Bone and joint infections are very common problems in foals and have been some of the first areas where clinical trials of HBOT have been applied to horses. Severe muscle infections from Clostridial infections secondary to injection reactions and a variety of tissue injuries are very similar to HBOT-treatable conditions in humans.

In medicine, it is common that a combination of treatments be used to achieve the maximal response for the patient. Our philosophy has been to consider HBOT as one additional part of our arsenal to the treatment process. It should be viewed not as a magic bullet, but as something that can help salvage injured tissue and optimize the body's healing processes.

Where are we now? Having (re)discovered HBOT as a medical treatment, we are trying to learn from human experiences and develop protocols appropriate for different conditions in the horse. Soon, more basic research using HBOT on the horse will become available to further guide our use of this technology for a variety of problems in our equine patients. The hope is that HBOT will offer a way to transform how we think about the treatment of injuries in horses; from acceptance of a prolonged healing time and tissue loss to enhancement and optimization of the healing process.

About the Author

Fairfield Bain, DVM, MS, Dipl. ACVIM, Dipl. ACVP

Fairfield T. Bain, DVM, MS, Dipl. ACVIM, Dipl. ACVP, specializes in internal medicine and pathology. He is an equine technical services veterinarian at Merck Animal Health.

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