The nurse reviews the arterial blood gas results of an assigned client and notes the laboratory report results pH of 7.30, [normal pH is 7.35 to 7.45] Paco2 of 58 mm Hg, [Normal Paco2 is 35 to 45 mm Hg] Pao2 of 80 mm Hg. [normal is 80-100] HCO3 of 27 mEq/L (27 mmol/L). [Normal HCO3 is 22-26] The nurse interprets that the client has which acid-base disturbance?