Medium altitude - 5000 - 10,000 feet - in relation to athletics, we are concerned with this altitude range. High altitude - greater than 10,000 feet. More than 40 million people live and work between 10,000 ft. (3048 meters) and 18,000 ft. (5486 meters). Barometric (air) pressure decreases as altitude increases. Example: as the weight of the column of air above the point of measurement decreases. However, the chemical composition of the atmosphere is uniform up to 20,000 meters. Po2 in dry ambient air at sea level = . 209 x 760 mm hg = 160 mmhg. Po2 in dry ambient air at 3048 meters (10,000 ft. ) = . 209 x 510 mm hg = 107 mm. Po2 in dry ambient air at summit of mt everest - 8848 meters (29,028 ft. ) = . 209 x. Oxyhemoglobin dissociation curve: only a small change in percent saturation of hemoglobin is observed with decreasing po2 until an altitude of about 10,000 ft.