Altitude-Induced Alkalosis

Altitude-induced alkalosis can occur at elevations above ∼15,000 feet if
supplemental oxygen is unavailable. The cause of altitude-induced alkalosis
is hyperventilation to increase O₂ levels in the lungs, which, at the same
time, increases the rate at which CO₂ is exhaled. As a result of hyperventilation,
CO₂(aq) levels in the blood are reduced, and, by Le Châtelier’s
principle, carbonic acid (H₂CO₃) levels are also reduced, which increases
blood pH levels (alkalosis). Because H₂CO₃ is spontaneously deprotonated
to form bicarbonate (HCO₃^–), which is a substrate for the enzyme
carbonic anhydrase, inhibition of carbonic anhydrase activity by the drug
acetazolamide decreases the rate at which H₂CO₃ is removed from the
blood. Carbonic anhydrase is a Zn²⁺-dependent metalloenzyme that has
a critical role in maintaining blood pH by catalyzing a reversible reaction
that controls the levels of HCO₃^– and CO₂(aq) in the blood.