Final answer:
The nurse should document the crackling sensation, known as subcutaneous emphysema, and notify the physician immediately as it may indicate a serious complication such as a pneumothorax.
Step-by-step explanation:
If a nurse palpates a crackling sensation of the skin around the insertion site of a chest tube in a patient who has had thoracic surgery, the nurse is detecting what is known as subcutaneous emphysema. This condition can occur when air leaks into the tissues under the skin from the chest cavity. The appropriate action would be for the nurse to promptly document the finding and notify the patient's physician, as it may indicate a complication such as a pneumothorax or improper chest tube placement. Additionally, the nurse should monitor the patient for any signs of respiratory distress or changes in vital signs, as these could suggest a more serious underlying problem.