Stroke Rehabilitation and Hyperbaric Oxygen Theraphy
Most people believe that a stroke is due to the death of brain cells. Brain cells are thought to die as a direct result of the interruption of blood flow and the resulting lack of oxygen to a part of the brain. This concept of what a stroke is has been dogma for at least the last 100 years. This traditional concept of infarction, that the brain tissue dies from a blood and oxygen shortage lasting more than a few minutes, is no longer valid. A different concept has been slowly evolving over the past 25 years that the death of brain cells occurs only when the flow of blood falls below a certain level (approximately 8-10 ml/100 gr./min.) while at slightly higher levels the tissue remains alive but not able to function. Thus in the acute stroke the affected central core brain tissue may die while the more peripheral tissues remain alive for many years after the initial insult, depending on the amount of blood the brain tissue receives.
Those brain areas that are injured and are not receiving enough blood flow as a result of the stroke or trauma are now referred to as the “ischemic penumbra.” This is the area that surrounds the central core of infarcted (dead) tissue. These “rim” tissues do not receive enough oxygen to function but do receive enough to stay alive. These brain cells have been described as “sleeping beauties,” “sleeping neurons,” or “dormant” or “idling neurons.” These neurons are non functional but anatomically intact and can be revived.
Another process that occurs during this first year is “neovascularization,” also known as “angiogenesis.” This is the process of forming new capillaries which extend from the surrounding healthy brain tissue into the areas of the ischemic penumbra. The outermost portions of the ischemic penumbra (those portions closest to normal brain tissue) are able to metabolize slightly since they are receiving more blood than the more centrally located ischemic tissues. This metabolism releases a breakdown product of ATP called adenosine. Adenosine is released from ischemic tissues when ATP is being utilized by the cell for repair processes. Adenosine is a vasodilator and also stimulates new capillaries to grow into the ischemic penumbra (neovascularization). Thus during the first year after a stroke or TBI, new blood vessels are stimulated to move into the ischemic penumbra to re-supply it with a new blood supply.
Unfortunately, the ischemic penumbral tissues closer to the infarct area usually are not receiving enough oxygen or nutrients to generate ATP either from aerobic or anaerobic metabolism. Due to the lack of ATP formation, adenosine is not produced and the formation of new capillaries does not occur. Thus the ischemic penumbra remains ischemic because the process of neovascularization is not able to be completed. This often results in a substantial amount of brain tissue that remains ischemic and non-functioning in the chronic stroke and TBI patient’s brain. This failure of natural healing processes is due ultimately to damaged blood vessels and their inability to provide oxygen and nutrients to those portions of the brain that are damaged.
How Hyperbaric Oxygen Works in Stroke
Hyperbaric oxygen works to improve stroke and TBI patients by repairing and generating new blood vessels to the injured parts of the brain. Once the ischemic tissues no longer suffer from a lack of oxygen, they are able to begin to repair the injured neurons, glial cells and extracellular matrix. The generation of new blood vessels occurs as a direct result of daily hyperbaric oxygen treatments. This does not occur with pure oxygen at normal atmospheric pressures. The number of treatments required varies for each individual but in our experience the best results occur when at least 60 daily treatments are done. If only 20 to 30 treatments are done, the patient will often experience “backsliding” and may lose some of the improvement they gained from the hyperbaric oxygen treatments. In addition, some patients will not even begin to improve until they have had more than 30 or 40 treatments.
People should be aware that HBOT is not a miracle treatment and as such there is no clear clinical evidence to prove that it works. There are many encouraging studies which suggest improvement but there needs to be some larger scale placebo controlled blinded studies. There is a wealth of outcome data from many HBOT centers around the world which have documented the results of individual stroke cases and many of these show very encouraging results.