title: Letter: Auditory guide to the extradural space.
mesh_terms: D000388:Air; D000767:Anesthesia, Epidural / Q000379:methods*; D003463:Cues; D006309:Hearing; D006801:Humans; D007267:Injections / Q000379:methods; D012965:Sodium Chloride
chemical_list: D012965:Sodium Chloride