1. The nurse is caring for a patient post-operative after hip replacement who is receiving patient-controlled analgesia (PCA) with morphine. The patient is exhibiting slow, shallow respirations (RR = 8 breaths/min). ABGs: pH 7.28, PCO2 55 mm Hg, HCO3− 24 mEq/L. Which intervention is the most critical for the nurse to implement first?