A patient has an arterial blood gas (ABG) drawn. The results are as follows: pH 7.3, PCO2 46, and HCO3 29. Based on these findings, what condition does this patient have?

This patient’s ABG shows a respiratory acidosis. A pH lower than the normal range of 7.35 to 7.45 indicates an acidosis (higher would be an alkalosis). A respiratory acidosis occurs when the pCO2 raises due to retention of CO2 in the blood (normal range is 35–45). This can be due to either reduced pulmonary function/failure of the lung to excrete CO2, overproduction of CO2 or a combination of both. In any case, the body’s response to this change is to offset it with a slow increase in plasma HCO3, which occurs in the kidney (normal range is 22–28). This compensation occurs slowly over several days. In metabolic acidosis, there will be a low pH, and also a low HCO3 and PCO2.