High altitude has generally been defined as an elevation above 2500-3000 m (approximately 8200-10,000 ft). In healthy persons, clinically significant changes are difficult to demonstrate at elevations lower than this. Many people live at high altitude and perform normal activities. Worldwide, more than 140 million people live more than 2500 m above sea level of these, 80 million live in Asia, and 35 million live in the Andean mountains where the major population density is at elevations exceeding 3500 m. There was little difference on basal pulse rate among the student residing at high and low altitude. At school level age ranged between 16 to 18 years as measured by calculating basal pulse rate for one minute. There was little effect of high and low altitude on resting pulse rate. On the male students level age ranged 16 to 18 years as measured by counting pulse rate for one minute. From sea level to high altitude, the percentage of oxygen remains constant at 20.93%; therefore, barometric pressure determines the partial pressure of oxygen (PO2) in ambient air. Barometric pressure decreases as one rises in altitude and moves toward the poles. The changing position of the sun in relation to the equator affects barometric pressure, producing a seasonal atmospheric tide.