Final answer:
When unable to withdraw fluid from a Salem sump nasogastric tube before initiating a feeding, the nurse's priority action is to obtain orders for a chest x-ray to confirm tube placement.
Step-by-step explanation:
When preparing to administer tube feedings through a Salem sump nasogastric tube, the priority action of the nurse upon being unable to withdraw fluid should be to confirm correct tube placement to ensure patient safety. Since the nurse is unable to aspirate any fluid, there is a risk that the tube could be misplaced. The correct and safe action would be option D, which is to obtain orders for a chest x-ray to confirm the placement of the tube before starting the feeding. Administering feed without confirmation of proper placement could lead to serious complications such as aspiration pneumonia if the tube is in the respiratory tract instead of the gastrointestinal tract. Injecting air and auscultating or changing the client's bed position will not provide the definitive confirmation needed in this situation.