Respiratory compensation process takes 12-24 hours to become fully active. Protons are slow to diffuse across the blood brain barrier. In the case of LA this will be faster because LA is produced in the brain.
The degree of compensation can be assessed by using Winter’s Formula. It is INAPPROPRIATE to use this formula before the acidosis has existed for 12-24 hours.
History would suggest AG acidosis is secondary to hypotension with lactic acid build up and the patient is not able to compensate with his COPD therefore there is no respiratory compensation and the non AG acidosis is secondary to diarrhea with associated HCO3 loss.