Torn or damaged tissues release fluids into interstitial spaces, the space between cells, causing edema (swelling).  As swelling increases, this causes more pressure on surrounding cells, tissues and blood vessels.  As these areas are squeezed from the increase of fluid and from the natural body response to increase inflammation (as a component of “first response” to an injury), more tissues die, more fluids are released and edema increases. As edema increases, there is more potential for this cascade effect to continue, causing more damage.  This is especially significant in cerebral edema as injury to the brain is compounded by swelling around the site of the initial injury, and extensive swelling within 48 hours may result in additional long-term disabilities from the destruction of brain tissue.  Hyperbaric oxygen reduces edema.  Reducing swelling in the brain lowers intracranial pressure and this reduction in edema decreases the cascade effect on compromised tissues, and the oxygen promotes the repair and healing of these areas.  Trapped fluid as the result of a disruption in the lymph or circulatory system can be reduced well after the initial trauma took place, which will promote healing to the area.