Ideal Cricoid Pressure Is Biomechanically Impossible During Laryngoscopy

Abstract

Objective: This study was a prospective, randomized controlled trial of rapid sequence intubation (RSI) with cricoid pressure (CP) within the emergency department (ED). The primary aim of the study was to examine the link between ideal CP and the incidence of aspiration.Method: Patients > 18 years of age undergoing RSI in the ED of two hospitals in New South Wales, Australia, were randomly assigned to receive measured CP using weighing scales to target the ideal CP range (3.060-4.075 kg) or control CP where the weighing scales were used, but the CP operator was blinded to the amount of CP applied during the RSI. A data logger recorded all CP delivered during each RSI. Immediately after intubation, tracheal and esophageal samples were taken and underwent pepsin analysis.Results: Fifty-four RSIs were analyzed (25 measured/29 control). Macroscopic contamination of the larynx at RSI was observed in 14 patients (26%). During induction (0-50 seconds), both groups delivered in-range CP. During intubation (51-223 seconds), laryngoscopy was associated with a reduction in mean CP below 3.060 kg in both groups. When compared, there was no statistically significant difference between the groups. For 11 patients, pepsin was detected in the oropharyngeal sample, while three were positive for tracheal pepsin. Seven patients (four control/three measured) were treated for clinical aspiration during hospitalization. As a result of the finding that neither group could maintain ideal range CP during laryngoscopy, the trial was abandoned.Conclusion: Laryngoscopy provides a counter force to CP, which is negated to facilitate tracheal intubation.The concept that a static 3.060 to 4.075 kg CP could be maintained during laryngoscopy and intubation was rejected by our study. Whether a lower CP range could prevent aspiration during RSI was not explored by this study. R apid sequence intubation (RSI) involves administration of anesthetic and neuromuscular blocking agents in rapid succession to facilitate endotracheal intubation.1 In a 1961 nonrandomized, uncontrolled case series, Sellick 2 described esophageal occlusion "by backwards pressure on the cricoid ring against the bodies of the cervical vertebrae" during RSI in 26 high-risk anesthetic cases. In three cases, release of the cricoid pressure (CP) after intubation was associated with immediate reflux into the pharynx of gastric and

Review article: Effectiveness and risks of cricoid pressure during rapid sequence induction for endotracheal intubation in the emergency department: A systematic review

“…was identified as a high‐quality observational study, and the registry by Ghedina et al 27 . and randomised controlled trial by Trethewy et al 28 . were identified as intermediate quality studies with a moderate risk of bias.…”

“…One randomised controlled trial ( n = 54) investigated the incidence of aspiration when CP operators could measure and aim to apply the target force of CP in comparison to when operators were blinded to the force of CP they were delivering 28 . In the pilot study, only 25% of operators applied the target force of CP; hence, this was deemed an appropriate control in the ED setting 30 .…”

“…An interesting conclusion made by Trethewy et al 28 . was that the recommended force of CP could not be maintained during laryngoscopy.…”

“…investigated the effect of CP on the incidence of aspiration and intubating conditions. They identified 12 studies; nine involving non‐RSI intubations in the operating room, two involving RSI in the operating room and the study by Trethewy et al 28 . included in this review involving RSI performed in the ED.…”

“…A common principle of medical research suggests that when an intervention is so ingrained in common practice, investigation into the intervention is not necessary 18 . This principle has likely prevented research into CP until only recently, with the first randomised controlled trial in elective surgeries published in 2001, and in RSI intubations in 2018 28,36 . However, because of the risks associated with CP and uncertainty surrounding its efficacy, it is important that further research is conducted to determine its safety and efficacy in current practice.…”