Ultrasonographic Appearance of the Cricothyroid Membrane

We read with great interest the important article by Siddiqui et al.¹  published in the November issue of Anesthesiology, demonstrating that the use of ultrasound guidance may improve the cricothyrotomy success rate in cadavers with difficult landmarks. We also read with great attention the nice Editorial View by Asai,²  which accompanies this article. One image (from J. P. Rathmell) in the center of the first page of this Editorial illustrates these two articles. Unfortunately, this picture does not seem to be an image of the cricothyroid membrane but, as much as we can see, an ultrasound image of the hyoid bone, represented “as an inverted U hyperechoic curvilinear line” as described by Singh et al.³  We understand that this image was not necessarily intended to present a true sonoanatomic view but was rather an artistic illustration of airway ultrasound. This might, however, be confounding for readers not familiar with ultrasound imaging of the airway because it is the only image illustrating these two articles. Furthermore, this image might lead to puncture failure and/or adverse events if anesthesiologists try to find a view similar to the one presented in the Editorial. The cricothyroid membrane located nearly 2 cm caudal to the hyoid bone has a characteristic ultrasound feature. In the transverse plane, it appears as a slight depression at the caudal border of the thyroid cartilage, framed by the lateral wings of the thyroid cartilage or the cricoid cartilage, according to the level of the scan (fig. 1). In the sagittal plane, it also appears as a depression of 7- to 12-mm long in adults, lying between the lower border of the thyroid cartilage and the upper border of the cricoid cartilage (fig. 2). This latter picture is in agreement with the description made by Kristensen.⁴  We hope this letter can help those who were interested in this topic.

The authors declare no competing interests.