A mountaineer attempts an assault on a high mountain in the Andes and reaches an altitude of 5000 meters (16,400 ft) above sea level. What will happen to his arterial PCO2 and pH?
A. Both will be lower than normal.
B. The pH will rise and PCO2 will fall.
C. Both will be higher than normal due to physical exertion.
D. The pH will fall and PCO2 will rise
Correct Answer: B. The pH will rise and PCO2 will fall.
The mountaineer will suffer from a respiratory alkalosis. The decline in the PO2 with altitude will stimulate breathing to offset the hypoxia. Carbon dioxide is driven from the blood faster than it is produced in the tissues so PCO2 falls and pH rises.