title: The sniffing position provides greater occipito-atlanto-axial angulation than simple head extension: a radiological study.
abstract: OBJECTIVE
  While the anatomic sniffing position has traditionally been considered the standard head and neck position for laryngoscopy, recent evidence suggests that the sniffing position provides no significant advantage over simple head extension. To establish if the sniffing position provides an anatomic advantage, we compared the occipito-atlanto-axial extension angle, a key determinant for obtaining a good laryngeal view during laryngoscopy, in simple head extension and sniffing positions.
  
  
  METHODS
  Thirty volunteers with normal cervical spines were studied. Radiological examinations of the lateral cervical spine were taken and compared in each of the following three positions for each subject: neutral position (flat on the table with no pillow and without head extension or flexion); simple head extension (head maximally extended without a pillow); and the sniffing position (head extension with cervical flexion obtained by 7 cm occipital elevation).
  
  
  RESULTS
  Mean angles of the occipito-atlanto-axial extension in simple head extension and the sniffing position were 20.4 degrees+/-5.1 degrees and 24.2 degrees+/-5.6 degrees, respectively (P<0.01).
  
  
  CONCLUSIONS
  The anatomic sniffing position provides greater occipito-atlanto-axial extension compared to simple head extension. These findings should be taken into consideration when optimizing patient positioning for laryngoscopy.
authors.affiliation: Department of Anesthesia, Nippon Steel Yawata Memorial Hospital, 1-1-1 Harunomachi, Yahatahigashi-ku, Kitakyushu 805-8508, Japan. takenaka.i@ns.yawata-mhp.or.jp
authors.forename: Ichiro
authors.initials: I
authors.lastname: Takenaka
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Aoyama
authors.forename: Tamao
authors.initials: T
authors.lastname: Iwagaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishimura
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Kadoya
mesh_terms: D000328:Adult; D001268:Atlanto-Axial Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D001269:Atlanto-Occipital Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D035843:Biomedical Research; D006257:Head / Q000033:anatomy & histology*; D006801:Humans; D007828:Laryngoscopy / Q000379:methods; D008297:Male; D009333:Neck / Q000033:anatomy & histology*; D011187:Posture / Q000502:physiology*; D011859:Radiography; D012016:Reference Values