Ideal Cricoid Pressure Is Biomechanically Impossible During Laryngoscopy

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.

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.

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.

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.