Editor's note: Doctors from Merrimack Valley Hospital occasionally contribute columns on health topics. This is one of those columns.
Hyperbaric oxygen therapy has been available for more than a century, but our understanding of the medical benefits it can provide in wound healing, bone infections and complications of radiation treatment has evolved considerably over the past 20 years.
In the modern wound and hyperbaric center, the use of the hyperbaric chamber is targeted to diabetic patients with severe grades of ulceration and infection, to patients with chronic bone infections as an adjunct to surgery and antibiotic treatment, and to patients with damage to bone, intestine or bladder from previous radiation treatment for cancer.
At normal pressures at sea level, red blood cells, which have a high affinity for oxygen and distribute it to the tissues, are almost completely saturated with oxygen, but very little oxygen is dissolved in the liquid component of blood, called plasma. Even breathing 100 percent oxygen at normal, ambient pressure will not increase the saturation of oxygen in the blood or the distribution of oxygen to the tissues.
To do this, we need to dissolve more oxygen in the plasma by raising the pressure of the gases we breathe. We can accomplish this by increasing the pressure in an enclosed chamber to at least twice the normal air pressure at sea level. This pressure is called 2 atmospheres absolute. For most therapeutic use, we aim for 2 atmospheres absolute to 2.5 atmospheres absolute for 90 minutes every day.
These pressures are approximately equivalent to an underwater dive of 30 to 50 feet. The number of treatments for diabetic foot ulcers is variable, averaging 35. For bone problems and radiation-related problems, we sometimes aim for 40 or more treatments.
Oxygen equals healing
Saturating the tissues of a wound with higher than normal levels of oxygen sounds like a good idea in general, because oxygen is needed for tissue healing, as we know.
But the effects of super-saturation with oxygen go beyond the obvious. What we have found through basic research, is that the level of growth factors produced by the cells in a wound increases substantially in the presence of high levels of oxygen.
These growth factors signal the cells to replicate themselves actively, to grow and fill the wound with new tissue. An important aspect of wound healing itself is the production of new blood vessels, a process called angiogenesis. Hyperbaric oxygen therapy has been shown to increase angiogenesis.
In the modern wound care center, hyperbaric oxygen has been demonstrated to be a useful adjunct in the management of certain types of chronic, non-healing wounds. These include diabetic foot ulcers, chronic bone infections called osteomyelitis, wounds associated with the sudden blockage of large or small arteries, and open wounds and other problems associated with bones or organs that have been injured by radiation.
How it helps fight diabetes
Diabetic patients are prone to ulcerations of the feet for many reasons, including nerve changes called diabetic peripheral neuropathy, impaired delivery of nutrients through the walls of tiny blood vessels called capillaries, decreased ability of the diabetic patient to fight infection, and often because of associated diabetic circulatory problems.
When the severity of the wound is such that the deeper structures of the foot (such as tendon or bone) are involved, or when there is dead tissue present, often associated with infection, treatment with hyperbaric oxygen in addition to aggressive treatment of the wound by surgical debridement, antibiotics for infection, and appropriate wound dressings, has been shown to speed healing and reduce the risk of amputation.
One of the earliest scientific studies to demonstrate medical benefit for hyperbaric oxygen treatment was carried out on patients who had undergone head and neck radiation for cancer and needed work done on their teeth.
Because of toxic effects of radiation on the jaw bone, dental work often failed to heal. Following a course of hyperbaric oxygen treatment, the result was a much higher success rate in oral surgery in this group of patients. The disease process, called osteoradionecrosis, remains one of the primary indications for hyperbaric oxygen therapy.
Treatment can help circulation, even frost bite
Other less common conditions that benefit from hyperbaric oxygen include carbon monoxide poisoning, gas gangrene, frost bite, sudden and recent blockages in the circulation, and decreased circulation in surgical flaps created by plastic surgeons.
Patients who are going to receive hyperbaric oxygen therapy are taught to clear their ears just like scuba divers because the pressure changes can produce ear fullness or even pain. If the pressure is not equalized by maneuvers such as swallowing or blowing, damage to the eardrum can occur. Fortunately, most people can readily learn how to clear their ears. The hyperbaric chamber itself is cylindrical in shape, made out of thick, clear plastic, so the patient can see out in all directions. Treatment sessions usually last for 90 to 120 minutes. The entire period in the chamber is carefully monitored by a technician who chats with the patient frequently during treatment.
While hyperbaric oxygen therapy should not be offered as the only treatment for non-healing diabetic foot wounds, bone infections and radiation injury, it is an important and proven adjunct in managing these conditions.
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Walter Kwass, M.D., a board certified vascular surgeon, is medical director of the Wound Care & Hyperbaric Center at Merrimack Valley Hospital.