ABG interpretation: pH 7.39; pCO2 65; HCO3- 37. Which pattern best fits this result?

ABG interpretation: pH 7.39; pCO2 65; HCO3- 37. Which pattern best fits this result?

• A. Compensated respiratory acidosis
• B. Compensated metabolic acidosis
• C. Uncompensated respiratory alkalosis
• D. Uncompensated metabolic alkalosis

Answer: (A)

When the pH is essentially normal but the CO2 is clearly elevated, think of a primary respiratory problem with metabolic compensation. Here the pCO2 is 65 mmHg, indicating respiratory acidosis. The bicarbonate is also elevated at 37, which shows the kidneys have increased HCO3- to counterbalance the acid load. The near-normal pH with a substantial bicarbonate rise points to a chronic process, since renal compensation takes time to develop. So the pattern is a compensated respiratory acidosis, with renal (metabolic) compensation bringing the pH toward normal. It wouldn’t be a primary metabolic disturbance because the CO2 remains high, nor an uncompensated respiratory alkalosis, which would have a low CO2 and a high pH.

When the pH is essentially normal but the CO2 is clearly elevated, think of a primary respiratory problem with metabolic compensation. Here the pCO2 is 65 mmHg, indicating respiratory acidosis. The bicarbonate is also elevated at 37, which shows the kidneys have increased HCO3- to counterbalance the acid load. The near-normal pH with a substantial bicarbonate rise points to a chronic process, since renal compensation takes time to develop. So the pattern is a compensated respiratory acidosis, with renal (metabolic) compensation bringing the pH toward normal. It wouldn’t be a primary metabolic disturbance because the CO2 remains high, nor an uncompensated respiratory alkalosis, which would have a low CO2 and a high pH.