AIRWAY/ORIGINAL RESEARCH Videographic Analysis of Glottic View With Increasing Cricoid Pressure Force Jaehoon Oh, MD; Taeho Lim, MD, PhD; Youngjoon Chee, PhD; Hyunggoo Kang, MD; Youngsuk Cho, MD; Jongshill Lee, PhD; Dongwon Kim, MD; Miae Jeong, MD Study 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. Conclusion: 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. [Ann Emerg Med. 2013;61:407-413.] Please see page 408 for the Editor’s Capsule Summary of this article. A feedback survey is available with each research article published on the Web at www.annemergmed.com. A podcast for this article is available at www.annemergmed.com. 0196-0644/$-see front matter Copyright © 2012 by the American College of Emergency Physicians. http://dx.doi.org/10.1016/j.annemergmed.2012.10.038 INTRODUCTION Background Cricoid pressure, first described by Sellick 1 in 1961, is a technique used to occlude the esophagus by compressing it between the cricoid cartilage and cervical vertebrae. This technique is intended to reduce the risk of aspiration during the induction phase of anesthesia. The recommended force applied during cricoid pressure is typically between 30 and 44 N (Newton; 1 N = 1 kg·m·s -2 ). 2-4 Rapid sequence intubation is an anesthesia induction technique designed to facilitate rapid intubation in patients with a high risk for aspiration and is the most frequently used intubation technique in emergency departments. 5,6 Cricoid pressure was recommended for intubation and as a standard component of rapid sequence intubation in emergency airway management. 6 However, according to the 2010 American Heart Association Guidelines, routine use of cricoid pressure to prevent aspiration in cardiac arrest is no longer recommended. 7 Magnetic resonance imaging of the neck with cricoid pressure demonstrates airway compression and lateral movement of the esophagus relative to the cricoid ring, bringing into question the anatomic foundation of the technique. 8 There is contradictory evidence about the effects of cricoid pressure on laryngoscopy and glottic view. 9-13 Although the application of cricoid pressure force (30 N) improved laryngoscopic view in one study, 9 another study reported increases in cricoid deformation and vocal cord closure, in addition to difficult mask ventilation with increasing cricoid pressure force. 10 In a cadaver study, bimanual laryngoscopy optimized the laryngeal view more effectively than cricoid pressure or the backward-upward-rightward pressure maneuver. 11 Most studies have used either the Cormack and Lehane grading system or the percentage of glottic opening score to measure the effect of cricoid pressure. 9-12 However, these scores are operator reported and few studies have used objective Volume , .  : April  Annals of Emergency Medicine 407