###HUMAN: count the number of patients whose admission year is less than 2156 and procedure long title is laryngoscopy and other tracheoscopy?, ###ASSISTANT: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN procedures ON demographic.hadm_id = procedures.hadm_id WHERE demographic.admityear < "2156" AND procedures.long_title = "Laryngoscopy and other tracheoscopy"