Comparison between ultrasound-guided and digital palpation techniques for identification of the cricothyroid membrane: a meta-analysis

Ultrasound identification of the cricothyroid membrane: the new standard in preparing for front-of-neck airway access

“…The meta-analysis by Hung and colleagues 4 unequivocally documents the superiority of ultrasound for guiding identification and marking of the cricothyroid membrane, and the limitations of palpation methods, especially in the obese and in those with pathology of the neck. The clinical consequences should be that, in cases where pre-induction visual inspection or palpation methods do not with certainty identify the cricothyroid membrane and the midline of the airway, the cricothyroid membrane should be identified with ultrasonography and marked with the patient in extended-neck position.…”

“…Concomittantly, patients with obesity or with airway/neck pathology are exactly the ones in whom we more often encounter serious airway problems, 1 including the need for emergency front-of-neck airway access. The relevance of having a special focus on these patient categories is confirmed by the meta-analysis: 4 studies that included either morbidly obese patients 6 or patients/cadavers with verified pathology of the neck 7,8 showed greater success with ultrasonography than with palpation, whereas studies with lean subjects without pathology showed less or insignificant differences between ultrasonography and palpation. One of the studies involved not only identification of the cricothyroid membrane, but also subsequent cricothyrotomy on cadavers.…”

“…When we combine these results with those of a previous review of ultrasonographic identification of the cricothyroid membrane, 5 which showed that in studies where one investigator performed all the scans, the success rate invariably reached 100%, we can conclude that ultrasonographic identification is superior to palpation and that, with sufficient training and practice, failure is rare. Although it did not reach statistical significance, the time taken with ultrasonography was longer in all but one of the studies, with a pooled weighted difference of 22 s. 4 So, how do we deal with this dilemma? We have one technique (palpation) that is not sufficiently precise, but faster when it works, and another technique (ultrasound guidance) that is more precise, but on average takes longer.…”

“…It has a reported 64% failure rate by anaesthesiologists, 1 frequently associated with tube/device misplacement 1,2 or failure to identify the cricothyroid membrane. 3 In this issue of the British Journal of Anaesthesia, Hung and colleagues 4 present a new meta-analysis confirming that palpation alone is associated with an unacceptably high failure rate and that ultrasonography is more successful than palpation in leading the clinician to identification of the cricothyroid membrane, and thus the position of the midline of the airway in the neck. In all studies in the meta-analysis involving adults, ultrasonography had a higher success rate of correct identification of the cricothyroid membrane, and the pooled relative risk of failure was 0.50 (95% confidence interval [CI]: 0.33e0.76; P¼0.001), indicating an overall important and significant superiority of ultrasound guidance over that of digital palpation techniques.…”

“…Combining the results from the two studies reveals that the marking returned to the correct position in all 34 cases. 18 Becoming competent at identifying the cricothyroid membrane and midline of the airway with ultrasonography In five of the eight studies in the meta-analysis, 4 the method for ultrasound-guided identification used was the longitudinal string of pearls technique described in 2011 5,13 (Fig. 2), and in two of these five studies, it was supplemented by the transverse thyroideairlineecricoideairline (TACA) approach.…”