What is the mechanism behind ventilatory acclimatization?
@Michael Kunh Carbonic anhydrase is used in the human body to tip the balance of the reaction  $H_2CO_3\rightleftharpoons H^++HCO_3^-$ to the right side, and is an important player in acidobasic homeostasis.

To answer the question:

$HCO_3^-$ is excreted through the kidneys. This represents the metabolic compensation to respiratory alkalosis that appears in altitude.

To summarize:


ascension leaves us in with a lower partial pressure of oxygen. This will stimulate the peripheral chemoreceptors of the carotid bodies and aortic arch to increase ventilation (hypoxic ventilatory response). In consequence, an acute respiratory alkalosis develops.
renal adaptation begins after more or less 8 hours, and reestablishes homeostasis after 24-48h. To do that, the kidney will excrete $HCO_3^-$, which will tend to acidify blood (metabolic acidosis to counterbalance respiratory alcalosis). To accelerate this phase, one could take some acetazolamide, a diuretic drug that causes $HCO_3^-$ excretion.