Using Sound Waves to Help a Cric

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Rai Y, You-Ten E, Zasso F, Castro CD, Ye XY, Siddiqui N. The role of ultrasound in front-of-neck access for cricothyroid membrane identification: A systematic review. J Crit Care 2020;60:161–8.

Background

This is a systematic review published in the Journal of Critical Care in 2020 reviewing the accuracy and efficacy of ultrasound for identification of the cricothyroid membrane (CTM) compared to digital palpation and evaluating the potential role in using ultrasound for cricothyrotomies in both patients with normal anatomy vs abnormal or difficult to palpate anatomy. It is well known that ultrasound has exploded in its application in both diagnostics and procedures and has ultimately revolutionized the way we practice medicine. With its growing use, more and more providers are comfortable using ultrasound for both identification of anatomy/pathology and to guide procedures that were previously only done with landmarks. While having the skills to perform landmark guided procedures is incredibly important, there is much value in being able to visually confirm anatomy to avoid procedure complications, especially when landmarks are difficult to palpate / identify in certain individuals. Ultrasound has also been studied for other airway related topics, such as confirming ET tube placement and also with pre-intubation assessment of the airway and aiding in predicting difficult airways.

Methods

The authors retrieved articles from the Ovid MEDLINE and EMBASE databases from 1946 to the present. Keywords included ultrasound and cricothyroid membrane. Studies were included if they were related to the use of US for CTM identification/cricothyrotomy and if studies were on human subjects over 12 years of age. This left them with 245 abstracts to  assess for eligibility.  Exclusion criteria included pediatric populations, experimental animal studies, irrelevant articles, duplicate records, and case reports. A total of 14 studies were included in the review. They were organized by time of study, population type, type of intervention, and outcome observed. All studies were assessed for risk bias (the Cochrane Collaboration risk of bias tool was used for randomized trials and the modified Newcastle-Ottawa quality assessment scale for cohort studies). 

Results

  1. In people with normal BMI/anatomy, ultrasound takes longer to identify the CTM without significant difference in accuracy of CTM identification

  2. Increased success with DP can possibly be achieved by using ultrasound guidance to practice palpation of neck landmarks.

  3. Pre-intervention and post-intervention markings were within 5mm of each other after a simulated failed airway.

  4. Ultrasound increases occurrence of correct airway device placement in cadavers with difficult anatomy (3.4 x improvement in identification of CTM).

  5. Airway insertion times are longer when ultrasound is used vs DP

  6. CTM depth significantly greater in obese patients

  7. Pre-marking for cricothyrotomy should be done in extension

Potential practice Applications based on Results

  • Consider ultrasound for CTM identification prior to difficult airways (pre-mark)

  • Consider using ultrasound regularly in airway evaluation to enhance palpation skills of airway anatomy

Limitations

This review included a variety of studies with many many different outcomes / measured variables, such as time for identification of CTM using ultrasound, the effect of using ultrasound to guide digital palpation,  the accuracy of using ultrasound for identification of CTM, and even one study about the time it takes to perform an ultrasound guided cricothyrotomy. It is difficult to extrapolate data due to the limited number of studies for each of the above endpoints, as well as the limited number and type of participants in the studies included.

Authorship

Written by Akansha Vaishnav, MD, PGY-3, University of Cincinnati Department of Emergency Medicine

Posting and Editing by Jeffery Hill, MD MEd, Associate Professor, University of Cincinnati Department of Emergency Medicine

Audio Editing by Anita Goel, MD, Adjunct Assistant Professor, University of Cincinnati Department of Emergency Medicine

Cite As: Vaishnav, A. Hill, J. Goel, A. Using Sound Waves to Help a Cric. TamingtheSRU.com. www.tamingthesru.com/blog/journal-club/us-for-cric. 6/11/2025