A nurse is reviewing the laboratory results of a client who is postoperative and has a respiratory rate of 7/min. The arterial blood gas (ABG) values include: pH 7.22 PaCO2 68 mm Hg Base excess -2 PaO2 78 mm Hg Oxygen saturation 80% Bicarbonate 28 mEq/L Which of the following interpretations of the ABG values should the nurse make?

A. Respiratory alkalosis: Respiratory alkalosis is characterized by a decreased PaCO₂ and elevated pH. In this case, the PaCO₂ is elevated, and the pH is low, which is the opposite of what occurs in respiratory alkalosis. B. Metabolic alkalosis: Metabolic alkalosis is indicated by an elevated pH and increased bicarbonate levels. The client’s pH is low, and although bicarbonate is slightly elevated, the primary disturbance is related to CO₂ retention, not a metabolic origin. C. Respiratory acidosis: Respiratory acidosis occurs when there is hypoventilation leading to CO₂ retention, which lowers the pH. The client’s ABG shows a low pH (7.22) and elevated PaCO₂ (68 mm Hg), consistent with acute respiratory acidosis, likely due to hypoventilation from a depressed respiratory rate. D. Metabolic acidosis: Metabolic acidosis is characterized by a low pH and low bicarbonate. While the pH is low, the bicarbonate is normal to slightly elevated, indicating that the primary problem is respiratory rather than metabolic.