Final answer:
Before inserting the Yankauer oral-tip catheter into the oropharynx, the nurse should apply suction by occluding the port.
Step-by-step explanation:
Before inserting the Yankauer oral-tip catheter into the oropharynx, the nurse should apply suction by occluding the port. This action ensures that the catheter is clear of any obstructions and ready to suction fluids or secretions from the oropharynx.