Altitude Sickness, a condition caused by reduced oxygen pressure at high altitudes, occurs in hikers as a consequence of relatively rapid ascent to high altitudes. Altitude sickness comprises a range of conditions, the most common being acute mountain sickness, which may be followed by two more critical conditions: high-altitude pulmonary edema or high-altitude cerebral edema.
The exact cause of altitude sickness is unknown, although researchers believe insufficient oxygen may impair the function of the sodium pumps located in cell walls.
The percentage of oxygen at sea level is roughly 21 nd the barometric pressure averages 760 mmHg. As altitude increases, the percentage remains about the same but the number of oxygen molecules per breath falls. In order to properly oxygenate the body, the breathing rate has to increase. The increased breathing rate raises the oxygen content in the blood, but not to sea level concentrations. Since the amount of oxygen required for activity is the same, the body must adjust to having less oxygen.
