The nurse is reviewing the arterial blood gas results of a client with chronic obstructive pulmonary disease (COPD) reporting dyspnea. The ABG results: pH 7.18 [7.35-7.45], PaCO2 67 mmHg [35-45 mm Hg], HCO3- 23 mEq/L [22-28 mEq/L]. The nurse should interpret these results to indicate that the client has