Airway/original research
Laryngeal View During Laryngoscopy: A Randomized Trial Comparing Cricoid Pressure, Backward-Upward-Rightward Pressure, and Bimanual Laryngoscopy

Presented orally at the Society for Academic Emergency Medicine annual meeting, May 2005, New York, NY.
https://doi.org/10.1016/j.annemergmed.2006.01.013Get rights and content

Study objective

External cricoid and thyroid cartilage manipulations are commonly taught to facilitate laryngeal view during intubation. We compare the laryngeal views during laryngoscopy with 4 manipulations (no manipulation, cricoid pressure, backward-upward-rightward pressure [BURP], and bimanual laryngoscopy) to determine the method that optimizes laryngeal view.

Methods

This was a randomized intervention study involving emergency physicians participating in airway training courses from December 2003 to November 2004. Direct laryngoscopies were performed with curved blades on fresh, non-fixed cadavers by using each of the 4 methods. The percentage of glottic opening (POGO), a validated scoring scale, was recorded for each laryngoscopy. Scores for bimanual laryngoscopy were recorded before the assistant applied external pressure.

Results

A total of 1,530 sets of comparative laryngoscopies were performed by 104 participants. One thousand one hundred eighteen of 1,530 sets (73%) had POGO scores less than 100 with no manipulation. Compared to no manipulation, mean POGO scores with bimanual laryngoscopy improved by 25 (95% confidence interval [CI] 23 to 27); mean POGO score improvement with cricoid pressure and BURP were 5 (95% CI 3 to 8) and 4 (95% CI 1 to 7), respectively. POGO scores with bimanual laryngoscopy were higher compared to cricoid pressure (mean difference 20, 95% CI 17 to 22) and BURP (mean difference 21, 95% CI 19 to 24). Among laryngoscopies with no manipulation in which the POGO score greater than 0 (n=1,434), laryngeal view worsened in 60 cases (4%, 95% CI 3% to 5%) with bimanual laryngoscopy, in 409 cases (29%, 95% CI 26% to 31%) with cricoid pressure, and in 504 cases (35%, 95% CI 33% to 38%) with BURP.

Conclusion

Using a cadaver model, we found pressing on the neck during curved blade laryngoscopy greatly affects laryngeal view. Overall, bimanual laryngoscopy improved the view compared to cricoid pressure, BURP, and no manipulation. Cricoid pressure and BURP frequently worsen laryngoscopy. These data suggest bimanual laryngoscopy should be considered when teaching emergency airway management.

Introduction

Tracheal intubation by direct laryngoscopy is the primary means of airway management in cardiac resuscitation, emergency care, and general anesthesia. Laryngeal exposure is the main determinant of success or failure with this procedure.

The 3 commonly used techniques for manipulating the external anatomy to help improve laryngeal view are the Sellick maneuver (involving cricoid pressure), backward-upward-rightward pressure (BURP, involving thyroid cartilage pressure), and bimanual laryngeal manipulation. Sellick1 in 1961 described backward pressure on the cricoid cartilage as a method for preventing passive regurgitation of stomach contents and also facilitating endotracheal intubation. In 1993, Knill coined the term “BURP,” describing the direction and pressure exerted on the thyroid cartilage by an assistant to improve laryngeal view at laryngoscopy.2 Bimanual laryngoscopy involves operator-directed manipulation of the thyroid cartilage (Figure 1).3, 4 Unlike cricoid pressure and BURP, both done by an assistant, bimanual laryngoscopy coordinates manipulation by the operator’s right hand with simultaneous direct observation. After the view is optimized, laryngeal manipulation is then taken over by an assistant at that location, which frees the operator’s right hand to place the tracheal tube.

Cricoid pressure and BURP are widely taught and now a standard aspect of resuscitation and airway training and are included in the American Heart Association’s Advanced Cardiac Life Support materials, as well as numerous other reference texts in emergency care.5, 6, 7 Bimanual laryngoscopy has been previously shown to be a simple and effective method of improving the laryngeal view.8 However, no study has directly compared BURP and cricoid pressure with the bimanual laryngoscopy technique and evaluated their impact on laryngeal view.

The objective of this study was to compare laryngeal view percentage of glottic opening (POGO) scores obtained during direct laryngoscopy using no neck manipulation, cricoid pressure, BURP, and bimanual laryngoscopy on fresh non-fixed cadavers to determine the method that optimizes laryngeal view.

Section snippets

Study Design, Setting, and Selection of Participants

This was a randomized intervention study that was conducted using 104 physician participants in emergency airway workshops from December 2003 to November 2004. The courses were taught for 2 days by the authors (R.M.L., W.J.L.) and included a detailed lecture series followed by a cadaver session in which the various techniques were performed.

Interventions

Participants were informed of the study objectives and all of the neck manipulation techniques had been discussed in the lecture component of the course.

Results

There were 1,530 sets of comparative laryngoscopies. The mean number of different cadavers (laryngoscopy sets) per participant was 15. The Table shows the experience levels of the participants. The POGO scores varied substantially between neck-manipulation groups when examined by ANOVA (all laryngoscopies: F3,6116=121.4, P<.0001; initial POGO scores <100: F3,6116=121.4, P<.0001). Figure 3 shows the POGO scores across all laryngoscopy maneuvers. Use of the bimanual laryngoscopy technique

Limitations

Our study should be interpreted with the following limitations. First, the use of a cadaver model is not a substitute for a live patient. However, we believe the cadaver model does approximate the mechanical feel and performance during laryngeal exposure of newly dead patients, such as in traumatic or cardiac arrest situations. Furthermore, it would be difficult to justify in anesthetized patients or cardiac arrest cases 4 randomly assigned laryngoscopies to investigate this subject. Second, we

Discussion

This study entailed a large number of emergency airway providers and a large number of laryngoscopies that compare laryngeal views with no manipulation, cricoid pressure, BURP, and bimanual laryngoscopy. Our results support the work of Benumof and Cooper 3 and others who have concluded that optimal external laryngeal manipulation is done by the operator’s right hand, with simultaneous observation of laryngoscopic view.4, 15, 16, 17, 18 Despite the fact that optimal external laryngeal

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      This maneuver can be critical during intubation, particularly during rapid‐sequence induction and intubation when the patient may be at higher risk of aspiration. However, using improper technique when applying cricoid pressure (ie, incorrect amount of pressure, wrong location) can lead to patient injury, including ruptured esophagus and laryngeal damage,2,3 as well as poor visualization during laryngoscopy.4 The team members involved in induction and intubation should be aware of the potential for harm caused by the incorrect amount or placement of pressure during cricoid pressure, particularly in the patient with an existing airway injury.3

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    Supervising editors: Kathy J. Rinnert, MD, MPH; Michael L. Callaham, MD

    Author contributions: RML, WCK, and WJL conceived, designed, and collected data for this study. RML and WWE analyzed and interpreted the data. WWE provided statistical advice. RML drafted the manuscript, and all authors contributed substantially to its revisions and intellectual content. RML takes responsibility for the paper as a whole.

    Funding and support: The authors report this study did not receive any outside funding or support.

    Financial disclosures: Dr. Levitan is a principal owner of Airway Cam Technologies, Inc. (Wayne, PA). Practical Emergency Airway Management courses during the study were run by Airway Cam Technologies, Inc. and sponsored by the American Academy of Emergency Medicine.

    Reprints not available from the authors.

    1

    Dr. Levitan is now with the Department of Emergency Medicine, Albert Einstein Medical Center, Philadelphia, PA.

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