Since CO2 + H2O <-> H2CO3 <-> HCO3- + H+
Increases and decreases in PCO2 directly affect the pH of the body and the CSF.
Even small changes of pH outside of the normal range 7.35 - 7.45 cause very significant changes in cell function.
Disregulation of the gas exchange in the lungs can cause acidosis or alkalosis.