Final answer:
When HCO3 levels increase, the PCO2 levels decrease as part of the body's mechanism for regulating acid-base balance.
Step-by-step explanation:
When the HCO3 levels increase in the blood, the PCO2 will be directly affected.
The increase in HCO3 levels will lead to a decrease in PCO2.
This is because HCO3 acts as a buffer that helps maintain the pH balance in the blood. As HCO3 increases, it combines with H+ ions to decrease the PCO2 levels.
This is an important mechanism in the body to regulate the acid-base balance.