In which client would the nurse be most likely to assess the signs and symptoms of an acid–base imbalance? A laboring client who is receiving an oxytocin infusion and who has been in the second stage of labor for 7 hours A client with chronic obstructive pulmonary disease (COPD) whose most recent arterial blood gases reveal a PCO2 of 51 mm Hg A client who has been admitted with a traumatic head injury and whose intracranial pressure is 18 mm Hg A client with a fluid volume deficit who has been receiving intravenous 0.45% NaCl for over 48 hours