title: Effects of sniffing position for tracheal intubation: a meta-analysis of randomized controlled trials.
abstract: BACKGROUND
  The purpose of this meta-analysis was to validate the efficacy of the sniffing position in the performance of intubation with direct laryngoscopy.
  
  
  METHODS
  We searched MEDLINE, the Cochrane Central Register of Controlled Trials, Embase, and Web of Science. Six randomized controlled trials comprising 2759 adult participants were analyzed. The DerSimonian-Laird method was used to calculate pooled relative risk (RR) and the 95% confidence interval (CI) of Cormack-Lehane classification, Intubation Difficulty Scale, success rate of the first intubation, and weighted mean difference of intubation time.
  
  
  RESULTS
  Compared with the other head positions, the sniffing position did not improve glottic visualization, success rate of the first intubation, or intubation time. However, the sniffing position was significantly associated with better Intubation Difficulty Scale compared with the simple head extension position. (RR,1.28; 95% CI, 1.15-1.42; p<0.0001) CONCLUSIONS: Although patients do not benefit from the sniffing position in terms of glottic visualization, success rate of the first intubation, or intubation time, the sniffing position can still be recommended as the initial head position for tracheal intubation because the sniffing position provides easier intubation conditions.
authors.affiliation: University Hospital Mizonokuchi, Teikyo University School of Medicine, Kawasaki 213-8507, Kanagawa, Japan. Electronic address: ypegtj25@yahoo.co.jp.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Akihisa
authors.affiliation: Division of Dento-Oral Anesthesiology, Tohoku University Graduate School of Dentistry, Sendai, 980-8575 Miyagi, Japan. Electronic address: hhoshi6@gmail.com.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hoshijima
authors.affiliation: University Hospital Mizonokuchi, Teikyo University School of Medicine, Kawasaki 213-8507, Kanagawa, Japan. Electronic address: maru555md@yahoo.co.jp.
authors.forename: Koichi
authors.initials: K
authors.lastname: Maruyama
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Kanagawa, Japan. Electronic address: yukihidekoyama1008@gmail.com.
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Koyama
authors.affiliation: University Hospital Mizonokuchi, Teikyo University School of Medicine, Kawasaki 213-8507, Kanagawa, Japan. Electronic address: psdelico06@yahoo.co.jp.
authors.forename: Tomio
authors.initials: T
authors.lastname: Andoh
mesh_terms: D006801:Humans; D007442:Intubation, Intratracheal / Q000379:methods*; D007828:Laryngoscopy / Q000379:methods*; D015233:Models, Statistical; D056888:Patient Positioning / Q000379:methods*; D016032:Randomized Controlled Trials as Topic