This study found it was mechanically impossible to maintain 30-40N of downward force during the laryngoscopy phase of RSI.
Why does this matter?
Several studies have called into question whether cricoid pressure (CP), aka Sellick's maneuver, makes any difference in the risk of aspiration of gastric contents during RSI. Anatomical studies show the esophagus is inadequately compressed or pushed laterally, and CP degrades laryngoscopic view. This study adds to the growing concern over this technique and showed that it did not appear possible to apply the recommended level of downward force. For a concise summary of why cricoid pressure is probably not best, see this from LITFL.
Stop pushing on my throat
This study started as a RCT that attempted to discover whether applying the recommended level of downward cricoid force (30-40N = roughly 3-4kg) would reduce pulmonary aspiration during RSI. When the force of CP was measured in operators who could visualize how hard they were pushing down vs controls who could not (54 patients, 25 measured/29 controls), neither could maintain 3-4kg (~30-40N downward force) during the laryngoscopy phase. Both groups were equally able to apply the correct force during induction, including the blinded control group. However, laryngoscopy provides a counter force to CP which is negated in order to facilitate tracheal intubation. The study was stopped after the first 70 patients were enrolled; 16 were excluded because the scale didn't work. The rate of clinical aspiration (antibiotic treatment for this during hospitalization) was 4 in the measured group/3 controls. Obvious laryngeal contamination during RSI occurred in 7 from each group. This study confirms my practice. I stopped using cricoid pressure a few years ago for lack of evidence for efficacy, lack of anatomic plausibility, and to improve first pass success by not degrading glottic view.
Ideal Cricoid Pressure Is Biomechanically Impossible During Laryngoscopy. Acad Emerg Med. 2017 Sep 28. doi: 10.1111/acem.13326. [Epub ahead of print]
Peer reviewed by Thomas Davis, MD.