A nurse is caring for a client whose arterial blood gas results show a pH of 7.3 and a PaCO2 of 50 mm Hg. The nurse should identify that the client is experiencing which of the following acid-base imbalances?

The correct answer is B: Respiratory acidosis. In respiratory acidosis, the pH is low (<7.35) and the PaCO2 is high (>45 mm Hg), indicating inadequate ventilation leading to retention of carbon dioxide. In this case, the pH is low at 7.3 and the PaCO2 is elevated at 50 mm Hg, consistent with respiratory acidosis.
Other options are incorrect because:
A: Respiratory alkalosis would present with a high pH (>7.45) and low PaCO2 (<35 mm Hg).
C: Metabolic acidosis would show a low pH and a normal or low bicarbonate level.
D: Metabolic alkalosis would exhibit a high pH and high bicarbonate level.