Intermittent hypoxia, often more commonly referred to as sleep apnea, is a condition where the human body is temporarily deprived of an adequate oxygen supply to the blood. The causes of hypoxia can vary and can be present in both children and adults. As well, some athletes and mountain climbers deliberately make use of the experience of oxygen deprivation at high altitudes to improve their performance when near sea level, which is known as intermittent hypoxic training (IHT). When intermittent hypoxia is an uncontrolled and prolonged condition, it is known to lead to impaired mental functioning and behavior, such as reducing academic performance in children and causing cardiovascular effects in adults including increases in blood pressure and possible changes in the normal heart rate.
The characteristic pattern of intermittent hypoxia when it is manifest as part of a sleep disorder is known to involve usually a few seconds on up to a few hours of activity where oxygen supply is reduced while sleeping. During this occurrence, time periods of normal breathing and oxygen supply known as normoxia also take place. While, in most instances of sleep apnea, an increase in the normal blood pressure level has been observed, the heart rate itself doesn't change as in cases of more protracted, chronic hypoxia. The signs of hypoxia can therefore be difficult to perceive for individuals who sleep alone, because most such individuals have no awareness of the intermittent hypoxia event upon wakening.
Managing hypoxia when it occurs during sleep involves conditioning patients to sleep on their side or in other positions where the tongue is less likely to block the airway while sleeping. Discouraging the use of alcohol and sleep medication is also part of treatment, as they have a tendency to overly relax throat muscles. More intense types of behavioral therapy may be required in severe cases, and other options like surgery on the throat or use of a mouthpiece that holds open the airway while sleeping, known as an Oral Appliance Therapy (OAT) device, are also possible long-term solutions to the problem.
Intermittent hypoxic training has been studied by Russian researchers since its benefits were first discovered. Spending time at high altitudes before returning to life near sea level has been shown to improve the overall health of everyday people and may be of significant benefit in treating several types of chronic illness. India has also documented lower incidences of disease rates in populations that have spent time at an altitude between 12,113 to 18,169 feet (3,692 to 5,538 meters) as compared to populations at lower levels, by studying the experiences of over 130,000 Indian Army soldiers. Bacterial infections, diabetes cases, and psychiatric illnesses, among other conditions, were all considerably lower in the group while they lived at increased altitude.
Additional research by the nations of Japan, the US, Australia, and Germany into intermittent hypoxia effects in 1990 has led to it being incorporated into athletic training programs. This included using the process by the Australian swimming team for the 2000 Olympics. Such conditioning is believed to directly improve upon the natural efficiency of the body to utilize oxygen. One medical condition for which intermittent hypoxia is closely tied to oxygen use like that of athletic performance is chronic fatigue syndrome (CFS). IHT has been shown to significantly improve the oxygen efficiency of sufferers of CFS after they have acclimated their bodies to concentration levels of 11% oxygen, where the overall effect of IHT is to reduce the body's need for oxygen by about 20% on average.