Final answer:
Local anesthetic is used during bronchoscopy to numb the trachea, preventing reflexive coughing or gagging caused by the endoscope, even under general anesthesia. This ensures the patient's comfort and safety during the procedure.
Step-by-step explanation:
A local anesthetic is sprayed into the trachea during a bronchoscopy, even when a patient is under general anesthesia, to specifically numb the trachea and prevent coughing or gagging reflexes during the procedure. While general anesthesia relaxes muscles and impairs autonomous functions such as breathing, requiring control to be handed over to the anesthesiologist, it may not fully suppress reflexive actions of the airway which can be stimulated during endoscopic procedures. Applying a local anesthetic directly to the tracheal mucosa ensures that the passage of the endoscope will not provoke these reflexes, thereby minimizing discomfort, potential injury, and complications during the procedure.
Furthermore, because general anesthesia can cause the tongue and other muscles to relax excessively, potentially leading to airway obstruction, endotracheal intubation is used as a preventive measure. Intubation ensures an open airway to the lungs and prevents the tongue from blocking the airway. However, despite these precautions, patients may experience a sore or scratchy throat post-surgery, partly due to the presence of the intubation tube and any reflexive actions that occurred if the local anesthetic was not used or was insufficient.