Respiratory Acidosis By James L Lewis III, MD, Brookwood Baptist Health and Saint Vincent's Ascension Health, Birmingham Reviewed / Revised Jul 2021 | Modified Sep 2022 View Patient Education Symptoms and Signs Diagnosis Treatment Key Points Topic Resources Arterial Blood Gas Interpretation... A-a Gradient Overview of Respiratory Acidosis Respiratory acidosis is primary increase in carbon dioxide partial pressure (P co 2) with or without compensatory increase in bicarbonate (HCO 3 −); pH is usually low but may be near normal.