What Is Hypobaric Hypoxia?

HIGH ALTITUDE

A significant portion of the world’s geography lies above 10,000 feet elevation. Some of this mountainous high altitude land is populated by indigenous people who have, over the centuries, adapted to this existence. These indigenous people have evolved mechanisms to more closely relate oxygen supply and metabolism and subsequent energy generation (Hoppeler and Vogt, 2001). Large numbers of people travel to high altitudes for recreational pursuits, such as mountaineering, trekking, and skiing. Those who travel acutely to altitude for short to moderate periods of time (e.g. skiers, trekkers, mountain climbers) or those who travel intermittently to altitude (e.g. highway construction workers, observatory workers, soldiers), typically

These sojourners (trekkers, tourists and specially troops) as well as people staying at high altitude (HA) such as local residents are exposed to hypobaric hypoxia. Ascent to high altitude leads to decreased partial pressure of oxygen in the atmosphere and resultant decrease in alveolar partial pressure of oxygen. This reduces oxygen diffusion to the pulmonary artery and causes subsequent reduction in oxygen saturation in the capillaries. Hence, the oxygen delivery to peripheral tissues is decreased leading to hypobaric hypoxia (Heath and Williams, 1977). The people who are exposed to hypobaric hypoxia are commonly confronted with mild problems such as acute mountain sickness (AMS), dizziness, nausea (Bahrke and Hale, 1993), hypophagia (Singh and Selvamurthy, 1993) and motor impairment (Hamilton et al., 1991) or severe problems such as HA pulmonary edema (HAPE), HA cerebral edema (HACE) (Baily and Davies, 2001; Baumgartner et al., 2002; Chao et al., 1999). Further, many of them experience mental dysfunction and memory deficit (Asplund et al., 1998). These problems become more severe due to lack of medical care at high

It can be distinguished as a zone where the cortex narrows into a single layer of densely packed pyramidal neurons 3-6 cells deep in rats, which curl into a tight U shape; one edge of the "U," field CA3, is embedded into a backward facing strongly flexed V-shaped cortex, the dentate gyrus. It consists of ventral and dorsal portions, both of which share similar composition but are parts of different neural circuits (Ekstorm et al., 2003). The hippocampus is known to contain two separate memory circuits. One circuit is used for recollection-based place recognition memory and includes the entorhinal-CA1 system while the other system is used for place recall memory and makes use of the CA3-CA1 system (Figure