The nurse in the emergency department (ED) is caring for a client with dyspnea and coughing up purulent sputum. The nurse reviews the arterial blood gas (ABG) results: pH 7.25 [pH 7.35-7.45], PaO2 93 mmHg [PaO2 80-100 mmHg], PaCO2 69 mmHg [PCO2 35-45 mm Hg], HCO3 25 mmol/L [HCO3 22-28 mEq/L]. The nurse should interpret these results to indicate that the client has