1. Airflow is governed by pressure. The normal atmospheric pressure is 760mmHg but at high elevations it is lower. Since pO2 diffuses from high to low pressure, not as much O2 will diffuse across the respiratory membrane. At low pressure, there is also low oxygen levels so a person will breathe faster in order to compensate for the lower oxygen levels.
2. Hyperventilation would cause an excess of CO2 to be excreted, which means that there is less H+ ions in the blood. The blood pH will rise