Monday 25 February 2019

Effect of Cricoid Pressure Compared with a Sham Procedure in the RSI of Anaesthesia: Old habits are dying hard

The use of cricoid pressure to prevent aspiration during intubation was never based on high quality evidence. Recently, it has been dying a slow death with many ED doctors abandoning this practice. But there still is controversy, and our anaesthetics counterparts are having trouble letting go.

Pulmonary aspiration during endotracheal intubation is exceedingly uncommon. The study of rare events requires enrolment of lots of patients to have the statistical power to come to an answer. As such it has not been feasible to get high quality RCT’s to inform practice.

These authors tried… but we are still not totally clear.

This was a double blind RCT non-inferiority trial conducted in 10 academic centres in France. 

Patients undergoing RSI in the operating theatre (not the ED) were randomised to proper cricoid vs. sham cricoid (hand was put in place, but no pressure applied).

The primary endpoint was aspiration and they also looked at several secondary outcomes.

They considered sham to be “non-inferior” if the incidence of aspiration was not more than 50% higher (i.e. relative risk of 1.5).


After enrolling 3472 patients they only had 10 cases of aspiration in the cricoid group vs. 9 in the sham. This gives a relative risk of 0.9.

Sham wins!?!

Not officially…

With such tiny numbers of aspiration, it is no surprise that the confidence intervals are rather wide. The 95% confidence interval was 0.33-2.38. This is greater than the non-inferiority margin of 1.5 and as such this is officially a negative study… i.e. they failed to demonstrate the non-inferiority of the sham procedure in preventing pulmonary aspiration.

From a purist EBM standpoint this may be a negative study, but many interpret this as another nail in the coffin for cricoid pressure. Outcomes were rare regardless. A look at the secondary outcomes shows worse laryngoscopic view and greater time to intubate with cricoid. There was really nothing to suggest any benefit from cricoid pressure.

If someone happened to “invent” cricoid pressure today, we would never take it up. But tradition, culture and "eminence-based" medicine is hard to kill.

Unfortunately, this study has the possibility of being misleading. Years from now, I imagine it will be casually mentioned as evidence in favour of cricoid pressure. This is precisely why it is good to dissect these papers, take the pressure off (pun intended) and to find the hidden truth.


Birenbaum A, Hajage D, Roche S, et al. Effect of Cricoid Pressure Compared with a Sham-Procedure in the Rapid Sequence Induction of Anesthesia. The IRIS Randomized Clinical Trial. Jama Surg 2019;154:9-17. [link to article]

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