A patient's arterial blood gas results are as follows: pH 7.37; pco2, 75 mm Hg; HCO3 -, 37 mmol/L. These values are consistent with

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

Answer: (A)

Interpreting ABG results starts by identifying the primary disturbance from PCO2 and HCO3-, then checking if pH indicates compensation. Here, the markedly elevated PCO2 (75 mm Hg) shows a primary respiratory problem causing CO2 retention and acidosis. The bicarbonate is also elevated (37 mmol/L), which reveals the kidneys have increased HCO3- to compensate. The pH is 7.37, within the normal range but slightly acidic, indicating that compensation has adjusted the pH toward normal but not completely. This pattern fits respiratory acidosis with renal (metabolic) compensation. It’s not an uncompensated respiratory acidosis because pH is not low, and it isn’t metabolic alkalosis or a non-respiratory disorder because the high HCO3- aligns with compensation for a respiratory cause.