 When taking the patient 's medical history , the subject is questioned about any significant signs or symptoms , such as difficulty in speaking or difficulty in breathing . These may suggest obstructing lesions in various locations within the upper airway , larynx , or tracheobronchial tree . A history of previous surgery ( e.g. , previous cervical fusion ) , injury , radiation therapy , or tumors involving the head , neck and upper chest can also provide clues to a potentially difficult intubation . Previous experiences with tracheal intubation , especially difficult intubation , intubation for prolonged duration ( e.g. , intensive care unit ) or prior tracheotomy are also noted . 
