During acclimatization, what happens to CO2 levels due to increased ventilation?

During acclimatization, what happens to CO2 levels due to increased ventilation?

• A. CO2 increases due to ventilation
• B. CO2 decreases due to ventilation
• C. CO2 stays the same
• D. CO2 fluctuates with activity

Answer: (B)

During acclimatization to high altitude, the body’s response to low oxygen is to increase ventilation (hyperventilation). This increased breathing rate and depth blows off more carbon dioxide, so arterial CO2 falls. The drop in CO2 causes a tendency toward respiratory alkalosis, which the kidneys then partially compensate for by excreting bicarbonate to bring pH back toward normal. Even as this compensation occurs, the CO2 level remains lower than at sea level while the hypoxic drive persists. So CO2 levels decrease due to the increased ventilation during acclimatization. The other options don’t fit because they’d require CO2 to rise, stay unchanged, or only fluctuate with activity, whereas the primary acclimatization response is increased ventilation lowering CO2.

During acclimatization to high altitude, the body’s response to low oxygen is to increase ventilation (hyperventilation). This increased breathing rate and depth blows off more carbon dioxide, so arterial CO2 falls. The drop in CO2 causes a tendency toward respiratory alkalosis, which the kidneys then partially compensate for by excreting bicarbonate to bring pH back toward normal. Even as this compensation occurs, the CO2 level remains lower than at sea level while the hypoxic drive persists. So CO2 levels decrease due to the increased ventilation during acclimatization. The other options don’t fit because they’d require CO2 to rise, stay unchanged, or only fluctuate with activity, whereas the primary acclimatization response is increased ventilation lowering CO2.