title: Videographic analysis of glottic view with increasing cricoid pressure force.
abstract: OBJECTIVE
  Cricoid pressure may negatively affect laryngeal view and compromise airway patency, according to previous studies of direct laryngoscopy, endoscopy, and radiologic imaging. In this study, we assess the effect of cricoid pressure on laryngeal view with a video laryngoscope, the Pentax-AWS.
  
  
  METHODS
  This cross-sectional survey involved 50 American Society of Anesthesiologists status I and II patients who were scheduled to undergo elective surgery. The force measurement sensor for cricoid pressure and the video recording system using a Pentax-AWS video laryngoscope were newly developed by the authors. After force and video were recorded simultaneously, 11 still images were selected per 5-N (Newton; 1 N = 1 kg·m·s(-2)) increments, from 0 N to 50 N for each patient. The effect of cricoid pressure was assessed by relative percentage compared with the number of pixels on an image at 0 N.
  
  
  RESULTS
  Compared with zero cricoid pressure, the median percentage of glottic view visible was 89.5% (interquartile range [IQR] 64.2% to 117.1%) at 10 N, 83.2% (IQR 44.2% to 113.7%) at 20 N, 76.4% (IQR 34.1% to 109.1%) at 30 N, 51.0% (IQR 21.8% to 104.2%) at 40 N, and 47.6% (IQR 15.2% to 107.4%) at 50 N. The number of subjects who showed unworsened views was 20 (40%) at 10 N, 17 (34%) at 20 and 30 N, and 13 (26%) at 40 and 50 N.
  
  
  CONCLUSIONS
  Cricoid pressure application with increasing force resulted in a worse glottic view, as examined with the Pentax-AWS Video laryngoscope. There is much individual difference in the degree of change, even with the same force. Clinicians should be aware that cricoid pressure affects laryngeal view with the Pentax-AWS and likely other video laryngoscopes.
authors.affiliation: Department of Emergency Medicine, College of Medicine, Hanyang University, Seoul, Korea.
authors.forename: Jaehoon
authors.initials: J
authors.lastname: Oh
authors.forename: Taeho
authors.initials: T
authors.lastname: Lim
authors.forename: Youngjoon
authors.initials: Y
authors.lastname: Chee
authors.forename: Hyunggoo
authors.initials: H
authors.lastname: Kang
authors.forename: Youngsuk
authors.initials: Y
authors.lastname: Cho
authors.forename: Jongshill
authors.initials: J
authors.lastname: Lee
authors.forename: Dongwon
authors.initials: D
authors.lastname: Kim
authors.forename: Miae
authors.initials: M
authors.lastname: Jeong
mesh_terms: D000328:Adult; D003413:Cricoid Cartilage / Q000033:anatomy & histology / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D005931:Glottis / Q000033:anatomy & histology* / Q000502:physiology; D006801:Humans; D007442:Intubation, Intratracheal / Q000379:methods*; D020704:Laryngoscopes; D007828:Laryngoscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011312:Pressure; D014741:Video Recording / Q000379:methods