A wound not caused by radiation is usually surrounded by relatively normal tissue. The amount of oxygen at the center of the wound is usually extremely low and the undamaged tissue usually has normal levels of oxygen. This difference in oxygen levels triggers a chemical reaction that promotes growth of blood vessels into the injury to allow healing to occur.

In radiation injury, this pattern is not the same. Radiation causes damage to tissue surrounding the center of the wound, with the damage gradually diminishing as the distance from the center of the wound increases. Because the center of the wound is not surrounded by healthy tissue, the oxygen levels are not different enough to trigger the chemical reaction that causes blood vessels to grow. Research in bone and soft tissue has shown that hyperbaric oxygen therapy can artificially create this difference in oxygen levels, triggering the growth of blood vessels.

Hyperbaric oxygen therapy increases the oxygen in tissue surrounding the wound by providing inhaled one hundred percent oxygen at pressure, raising the body's oxygen level ten to thirteen times above normal. Our belief at the Brain Radionecrosis Center is that this same thing can happen in brain radionecrosis.

Figure 2. The hypothesized mechanism of action of hyperbaric oxygen therapy in brain radionecrosis.
ENLARGE

In addition to triggering the growth of new blood vessels, hyperbaric oxygen therapy also reduces the swelling in the brain that causes the worsening of symptoms. This happens because the extra oxygen in the blood means the parts of the brain that were working without enough oxygen get the extra oxygen they need. This increased oxygen level helps to reduce the swelling caused by the low oxygen environment. The diagram (Figure 2.) shows how it is believed the extra oxygen helps to heal the brain radionecrosis injury.