Final answer:
If the HCO3 levels decrease, it can lead to metabolic acidosis, and the PCO2 would decrease as a compensatory mechanism.
Step-by-step explanation:
If the HCO3 levels decrease, it can lead to a condition called metabolic acidosis.
In this condition, the body has lower-than-normal amounts of bicarbonate in the blood.
As a compensatory mechanism, the PCO2 (partial pressure of carbon dioxide) would decrease as the body tries to reestablish the proper balance between bicarbonate and carbonic acid/CO2.