Effect of Cricoid Pressure Compared with a Sham Procedure in the Rapid Sequence Induction of Anesthesia. The IRIS Randomized Clinical Trial.

Birenbaum A, Hajage D, Roche S et al .

JAMA Surgery 2018. Published online October 17, 2018. doi:10.1001/jamasurg.2018.3577 

Aim and Hypothesis

Hypothesis: Incidence of pulmonary aspiration is not increased when cricoid pressure is not performed during RSI

Primary Outcome

Incidence of pulmonary aspiration detected visually at glottis during laryngoscopy OR tracheal aspiration just after intubation.

Secondary Outcomes

1) Frequency of suspected aspiration pneumonia in 24 hours

2) Difficult tracheal intubation

3) Traumatic complications owing to tracheal intubation and cricoid pressure


Rapid sequence induction mitigates risk of aspiration

Pulmonary aspiration risk is 0.03% in elective patients – however this is significantly higher in emergencies with varying statistics reported. The debate of the actual efficacy of cricoid pressure is not new, and can result in the following:

* Inadequate oesophageal occlusion

* Airway obstruction

* Poor view

* Operator variability

* Traumatic injury (rare)

Cohort and Study Inclusion

Data collected from February 2014 and February 2017.

The standard for anaesthesia & intubation was set as per French Guidelines (SFAR).

Many decisions during intubation were left up to the clinician such as the insertion of an NGT and PPI cover. The patients were pre-oxygenated to >90% ETO2 OR 4 FVC breaths. The hypnotic agent was up to the clinician and included: propofol/thiopentone/etomidate/ketamine.

The use of rocuronium for paralysis was not authorised.

Eligible Excluded
Any type of surgery requiring GA + RSI Patient refusal
>18 years old <18 years old
< 6 hours of fasting Pregnancy
≥1 Risk factor for aspiration :


BMI > 30

Gastric surgery


<48 hrs post-partum


Diabetic gastroparesis

Hiatus hernia


In a concurrent trial
Lack of National health care insurance
Contra-indications for cricoid/sux
Pneumonia/pulmonary contusion
URT abnormalities
Means of intubation other than laryngoscopy.

Statistical Analysis

An estimate chosen by paper of 2.3% as the incidence of pulmonary aspiration, based on a paper from 2011 with similar resource settings. The sham procedure was considered non-inferior to the cricoid pressure if the relative risk of aspiration was < 1.5.

Qualitative data was compared using the Pearson Chi Squared test, Fisher exact test or Cochrane Armitage test.

Analysis performed using R-software, version 3.4.1.


3472 patients were randomised, with 1735 in the cricoid arm, and 1736 in the sham arm.  The primary end point, pulmonary aspiration, occurred in 10 patients in the cricoid pressure group (0.6%) and 9 patients in the sham group (0.5%). Although the relative risk of the study was < 1.5, the upper limit of the 95% confidence interval was 2.0 and therefore greater than 1.5, rendering the result non-significant with a p-value of 0.14. Secondary end points were not significantly different between the two arms, however it was noted that the use of cricoid prolonged intubation time – more took over 30 seconds compared to the sham group (p<0.01)


Results cannot be applied to outside of the operating room. It does not translate to environments such as the ED, ITU and obstetric theatres. The study was set in an urban academic centre and may not extrapolate to UK district general hospitals. As a large proportion of RSIs are in the paediatric and pregnant populations, as are aspiration pneumonias, this has little evidence for not using cricoid.


Managing to standardise the anaesthesia, tracheal intubation, cricoid pressure procedures. Cricoid pressure technique was taught and practiced particularly well to control operator dependent variability.


This large RCT demonstrated a low incidence of pulmonary aspiration  in the context of RSI as a whole. They identified that delivering safe and effective cricoid is variable and that 47-63% operators improperly apply pressure. As a result, no RCTs can sufficiently produce data on application of cricoid pressure in RSI.

The primary end point is based on laryngoscopy which aimed to reduce risk of loss to follow up.

Excludes aspirations occur intra/post operatively that cannot be prevented by cricoid.

Study failed to demonstrate non inferiority due to an expected aspiration rate 2.8%. The comparative study had higher rate due to setting (OR vs non OR), use of suxamethonium, higher use of propofol, fewer cardiac arrests.

The actual aspiration incidence in this study was 0.6%. There were no differences in secondary end points however cricoid pressure increases duration of intubation and laryngeal exposure without affecting difficulty intubation.

Summary by Dr T Gupta. Journal Club Meeting 25 October 2018.

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