Quick question of buffering action of bicarbonate in acidosis?

Hello everyone,

Bicarbonate concentration reduces in acidosis. My question is where actually does this buffering take place and why it reduces?Do Hydrogen ions move into cells (like red blood cells), where they are buffered by bicarbonate. I'm talking about this reaction that occurs inside cells

CO2 + H20 <-> H2CO3<-> H+ + HCO3-

If this is the case why does bicarbonate in extracellular fluid decrease. Is it because the reaction I mentioned above occurs, in reverse direction and there is less efflux of bicarbonate from cells. Also does bicarbonate from extracellular fluid move into cells, to carry out this reaction.

or

Are hydrogen ions buffered in extracellular fluid by bicarbonate. Does the same reaction occur in extracellular fluid as well.

Thank you