The nurse is caring for a 78-year-old client admitted to the medical intensive care unit in respiratory distress. Based on the client’s assessment findings and arterial blood gas (ABG) results, which acid-base imbalance should the nurse identify?

A. Uncompensated respiratory acidosis: The ABG shows a pH of 7.2 (acidemia) and an elevated PaCO₂ of 51 mm Hg, indicating primary respiratory acidosis due to hypoventilation and CO₂ retention. The HCO₃⁻ is within normal range (26 mEq/L), showing no metabolic compensation has occurred. This reflects acute ventilatory failure, likely from impaired gas exchange. B. Compensated respiratory alkalosis: Respiratory alkalosis would present with an elevated pH and decreased PaCO₂ due to hyperventilation. Compensation would involve decreased HCO₃⁻. In this case, the pH is low and PaCO₂ is elevated, which is the opposite pattern. C. Metabolic acidosis with compensation: Metabolic acidosis would show decreased pH and decreased HCO₃⁻, with compensatory hyperventilation leading to a low PaCO₂. Here, HCO₃⁻ is normal and PaCO₂ is elevated, indicating the primary issue is respiratory, not metabolic. D. Uncompensated metabolic alkalosis: Metabolic alkalosis is characterized by elevated pH and elevated HCO₃⁻. This client has acidemia and normal bicarbonate levels, ruling out a metabolic alkalosis process.