Final answer:
Increasing elevation leads to a decrease in atmospheric pressure, making it more difficult for the body to achieve the same level of oxygen saturation. Hemoglobin saturation is lower at high altitudes compared to sea level.
Step-by-step explanation:
An increase in altitude results in a decrease in atmospheric pressure. Although the proportion of oxygen relative to gases in the atmosphere remains at 21 percent, its partial pressure decreases. As a result, it is more difficult for a body to achieve the same level of oxygen saturation at high altitude than at low altitude, due to lower atmospheric pressure.
For example, hemoglobin saturation is about 67 percent at 19,000 feet above sea level, whereas it reaches about 98 percent at sea level.