Could a treatment developed for injured deep sea divers help your horse recover from injury or infection? It sounds far-fetched--and this treatment, hyperbaric oxygen therapy, isn't a silver bullet. But as a complementary therapy, used alongside conventional medical and surgical treatments, it can aid healing and speed recovery in many situations.
Hyperbaric oxygen therapy works by increasing the flow of oxygen within body tissues. It was originally used to help divers recover from decompression sickness, a condition called "the bends" because its victims bend over in pain. When divers ascend quickly from deep water, bubbles of nitrogen gas may form in their lungs, tissues and blood. (Think about what happens when you open a can of soda--the release of pressure prompts bubbles to form.) That can damage blood vessels and disrupt blood flow, with deadly results. To neutralize the effects, the diver goes into an airtight, pressurized chamber to breathe pure oxygen. Then the pressure is slowly returned to normal, mimicking a slow ascent.
It's safe to say that your horse won't be scuba diving. But in human medicine, hyperbaric oxygen is now used for a wide range of conditions that are helped by getting more oxygen to the tissues-and horses suffer from many similar conditions. "We extrapolate from human protocols," says Kirsten Johnson of Kentucky Equine Sports Medicine and Rehabilitation Center (KESMARC) in Versailles, Kentucky. Kirsten and her husband Hub, founders of KESMARC, have made wide use of hyperbaric oxygen and also head Equine Oxygen Therapy, a Kentucky-based manufacturer and distributor of hyperbaric oxygen chambers for horses.
WHY IT HELPS
Every cell in your horse's body needs oxygen to function, and oxygen is essential for proper healing of skin, muscle, bone and other body tissues. Normally your horse gets all he needs just by breathing air, which is 21-percent oxygen (at sea level). Oxygen is transported from his lungs to his tissues by circulating blood. Hemoglobin, a component of red blood cells, binds to oxygen and carries most of it. A much smaller amount of oxygen (only about 1 .S percent of the total transported in the blood) is dissolved directly in the plasma, the liquid portion of blood. When the blood reaches the capillaries-the tiny blood vessels that serve tissues throughout the body-the oxygen diffuses into the tissues.
But there are times when the blood can't deliver enough oxygen to meet the body's needs-because circulation is blocked or disrupted, for example, or because an infection or other condition interferes with oxygen transport. You might expect that breathing pure oxygen would help in these cases, but that in itself doesn't dramatically change the oxygen level in blood. The amount of oxygen dissolved in blood plasma may increase by a small amount, but the red blood cells can't pack more than they normally do.
In hyperbaric treatment, the horse breathes pure oxygen at pressures two to three times greater than normal air pressure at sea level. The increased pressure causes significantly more oxygen to dissolve in the blood plasma. It diffuses farther outward from the capillaries, even reaching areas with restricted circulation. Up to 10 times more oxygen may reach body tissues, improving cell function and helping to speed tissue repair.
"It supports tissue healing, wherever the tissue is," explains Dennis Geiser, DVM, associate professor in the Department of Large Animal Clinical Sciences at the University of Tennessee College of Veterinary Medicine. The treatment is still fairly new to veterinary medicine, and there is very little research documenting its effects in horses. "The evidence is largely anecdotal, from case reports," he says. Nevertheless, the list of equine conditions that may benefit from it is growing.
HOW IT'S USED
Hyperbaric oxygen is a primary (first-line) treatment for a few conditions. At UT, Dr. Geiser says, these include
Smoke inhalation. Carbon monoxide, which is a byproduct of combustion, binds to red blood cells and blocks delivery of oxygen to the body. Hyperbaric oxygen helps overcome the effects by speeding the clearance of CO from the body, restoring oxygen delivery and reducing toxic effects.
Anaerobic infections. These infections are caused by bacteria that thrive in low-oxygen environments. They include post-injection reactions (clostridial myositis) and gas gangrene, which eats away soft tissues and releases toxins into the bloodstream. The high doses of oxygen delivered by hyperbaric therapy inhibit the bacteria and their toxin production. (Antibiotics are often used in conjunction with hyperbaric treatment to wipe out these infections, Kirsten notes.)
Typically, hyperbaric oxygen is a complementary treatment, used alongside conventional treatments. Here's a short list of conditions that it may help:
Wounds. The treatment is especially useful for large or compromised (non-healing) wounds and those where the blood supply is disrupted by swelling or tissue damage-crush injuries, for example. It can help reduce swelling and spur the development of new blood vessels and connective tissue, and it can encourage new skin to form.
Infections. Besides its use for anaerobic infections, hyperbaric therapy is used as a complementary treatment for difficult infections that don't respond to antibiotics alone, including bone, joint, and some soft-tissue infections. The combination of antibiotics and high oxygen levels seems to help the body fight the infection, Dr. Geiser says, and the effects of some antibiotics are enhanced by oxygen. High oxygen levels also increase the killing power of infection fighting white blood cells.
Burns. In human medicine, hyperbaric oxygen is often used for treating burn victims, and it can help horses burned in accidents and barn fires, too. It helps fight infection and encourages burned areas to close over with new tissue quickly.
Tendon and ligament injuries, Tendons and ligaments have poor blood supply and heal slowly. Hyperbaric treatment can speed up the process by pushing more oxygen into the injured site and encouraging healing to take place. (See the box at right for a report on some cases treated at UT.)
Head trauma. Swelling within the confines of the skull restricts blood flow and oxygen supply to the brain, damaging brain tissues. Hyperbaric therapy helps get oxygen to the area and reduce the swelling. "In people, it's used in stroke treatment," Dr. Geiser notes. It's also helpful for spinal-cord conditions that involve swelling.
Neonatal maladjustment (dummy foal syndrome). Newborn "dummy" foals show a range of symptoms depression, failure to nurse, aimless wandering, head pressing and, sometimes, convulsions. Lack of oxygen at some point during birthing is thought to be the cause. If the problem is caught in time and the foal gets supplemental nutrition and other intensive care, it can recover. Hyperbaric oxygen appears to help the recovery.
Colic. Hyperbaric oxygen can be used after colic surgery to reduce swelling, Dr. Geiser says, and it seems to speed healing. It may help prevent reperfusion injury, a complication that can occur after surgery to correct colon torsion (a twisted colon).
Acute laminitis. Inflammation and disruptions in circulation play a role in this condition, in which connective tissues between the hoof and inner structures of the foot break down. Hyperbaric treatment, along with drugs and other treatments to block inflammation and support the foot, seems to help minimize the destruction.
Respiratory problems. The treatment has been used for "bleeders" (horses who suffer exercise-induced pulmonary hemorrhage), Kirsten says. KESMARC is working with researchers at the University of Kentucky who are investigating this use.
These aren't the only situations where hyperbaric oxygen can be helpful. Spider bites, sinus infections, abscesses in the lungs or abdomen, and uterine infections are some other suggested uses. The treatment can be used to help equine athletes recover from stress, Kirsten says-pro football players use it this way.
WHAT TO EXPECT
One reason that hyperbaric oxygen isn't widely used for horses is that it's not widely available. An equine hyperbaric chamber obviously has to be a lot bigger than a chamber for human use. Dr. Geiser, who heads the Veterinary Hyperbaric Medicine Society, knows of about 16 nationally. So far, Tennessee is the only university that has one. "Many are at rehabilitation centers and equine clinics that deal with racehorses. There are some in California, Tennessee, Kentucky, Florida and other East-Coast states, with a smattering across the country," he says. "As success stories get out, there is more demand and more chambers are popping up."
There are basically two styles of chambers. Equine Oxygen Therapy produces stall-like chambers with a 10-foot diameter and 12 foot ceiling. A Canadian firm, Equineox Technologies Ltd., makes smaller stationary and mobile chambers set up like horse trailers. The University of Tennessee, which has offered hyperbaric therapy for about seven years, started out with one of the trailer-style chambers. Horses generally had to be sedated for the treatment. Recently, the university installed a stall-style chamber. "Horses can move around and lie down. They get used to it quickly, and we don't need to sedate them," Dr. Geiser says.
A session in a hyperbaric chamber is sometimes called a dive, a nod to the history of the treatment. Once the horse is inside and the door is sealed, oxygen is released into the chamber until the pressure is two to three times the air pressure at sea level-the equivalent of being 33 to 66 feet underwater. The horse typically stays inside at the desired pressure for 45 minutes to an hour, while a technician keeps an eye on him from outside. Then the pressure is slowly returned to normal.
The treatments vary with the condition. A horse being treated for smoke inhalation might be in the chamber twice a day, Dr. Geiser says. "For laminitis, we might use the chamber daily for three or four days and then, if the horse is responding well, go to every other day." For a severe wound, it might be once every other day. A post-op colic case might get daily treatments for three days. An athletic injury like a torn tendon or ligament might benefit from a couple of weeks of daily treatments.
Kirsten adds that the odds of a good outcome are best when hyperbaric oxygen is coordinated with the appropriate medical and surgical treatments. "It's only as good as the medicine it's practiced with," she says. "For example, to help get antibiotics to the cells to fight infection, you plan the hyperbaric therapy around the antibiotic treatment."
Costs vary regionally. At KESMARC, hyperbaric sessions are typically $400; the center offers a package price for 10 sessions.
The cost means that, for most people, this treatment won't be undertaken lightly. "Many rehabilitation centers take patients directly, but an owner should work through a veterinarian to be sure that the horse's condition will actually benefit from the treatment before he or she ships the horse and spends the money," Dr. Geiser says
For help locating a facility that provides hyperbaric oxygen therapy, contact Dr. Geiser at DGeiser@utk.edu.
Success Story: SUSPENSORY TEARS
Veterinarians at the University of Tennessee have combined two cutting-edge treatments, hyperbaric oxygen and stem-cell therapy, to successfully treat horses with torn suspensory ligaments. These injuries can be devastating. The ligament, which runs down the back of the lower leg and helps support the fetlock, heals slowly; it's often six to nine months and sometimes a year before the horse is back in work. The suspensory also tends to heal poorly, with a disorganized tangle of scar tissue taking the place of the long, strong fibers of springy collagen that make up a healthy ligament. As a result, the ligament is weaker, less elastic and more prone to injury.
"We were aware of research carried out at the University of Pennsylvania showing that, in people, hyperbaric oxygen increases stem-cell mobility. Since stem cells are being used to treat suspensory injuries in horses, we thought we'd try the two together," Dr. Geiser says. Stem cells have the ability to transform into different types of tissue. Injected into torn ligaments, they become fibroblasts--cells that make collagen.
The veterinarians used the combined treatment for three horses that had torn suspensory ligaments in their hind legs, following stem-cell injections with 15 days of daily hyperbaric treatments. Two of the three horses responded to the combined therapy; one, an event horse, was back in work in three months,
"Using the two treatments together appeared to improve the outcome," says Dr. Geiser. "We found that it seemed to speed healing, and the alignment of new fibers that filled in the lesions was stronger."
Source Citation:Pascoe, Elaine. "Hyper-healing: developed for treating decompression sickness in deep-sea divers, hyperbaric oxygen therapy is being used to help heal a variety of conditions in horses." Practical Horseman 36.11 (Nov 2008): 58(6). Academic OneFile. Gale. BROWARD COUNTY LIBRARY. 7 Sept. 2009
Gale Document Number:A188351765
Disclaimer:This information is not a tool for self-diagnosis or a substitute for professional care.
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