Without a steady and regular supply of oxygen, human beings inevitably die. Even significant interruptions of oxygen can cause serious and sometimes lasting or fatal consequences. The cause of diminished oxygen supply to the brain can be environmental, a situation termed hypoxic hypoxia. Fire fighters, mountain climbers, divers and aviators are vulnerable, as is anyone who suddenly chokes or has his or her airway blocked because of strangulation, or a crushed windpipe. Those who have severe asthma may also experience this condition.
A second type of hypoxia is called hypemic, and refers to reduced oxygen flow to the brain even though there is an adequate supply in the environment. Anemia and carbon monoxide poisoning are the most common causes. Stroke, heart attacks and shock can cause ischemic hypoxia, reduced oxygen to the brain resulting from inadequate blood circulation. Finally, in histotoxic hypoxia, the oxygen present in brain tissue cannot be properly metabolized, such as in cases of cyanide poisoning.
It is important to understand the nature of the symptoms of hypoxia. The person will begin to have difficulty mastering complex learning tasks, and will start to experience memory loss. Over time, the skin may begin to appear bluish, motor control may be lost, and the person may lose consciousness. In the most desperate of cases, seizures, coma, cessation of brain stem reflexes, and brain death will result. Assessing the degree of hypoxia can be difficult. Testing blood oxygenation levels only is effective in cases of hypoxic hypoxia. The most important priority is to remove whatever is causing the deprivation of oxygen and restoring normal flow to the brain. Inhaled oxygen and even life support are just some of the options available.
Brain damage can occur both during and after the hypoxic episode. While this episode is occurring, cells can die due to the increased acidity in the brain tissue. During this time, free radicals also build up. When oxygen is restored, they oxidize and can cause further injury.
In minor cases of hypoxia, the patient often fully recovers. However, in more severe instances, long term disability is quite possible. The degree and nature of the damage will depend on how long the person was deprived of oxygen, how quickly it was fully restored, and the area of the brain that was affected. Damage to the left side of the brain typically causes deficits in speech and language, while injury to the right affects a person’s ability to interpret emotions or perceive accurately. Damage on either side can cause paralysis of the opposite side of the body.
In all cases of severe hypoxia, it is important that the patient and his or her family become a part of a multi-disciplinary team whose members are expert in assessing functioning and guiding the patient and care-givers through the rehabilitation process. Since each brain injury is different and brings with it a unique set of challenges, this competent and loving support system will be invaluable in assisting the patient to make the best possible recovery.