Okay so I may have completely made this bit of history up, but this collection of complaints seems to be widely cited as being behind cricoid pressures descent from favour in recent times, especially with it’s partnering question of ‘Does it actually do anything?’ If you have been following some of the stuff at SMACC Gold through Twitter (or been lucky enough to actually attend) you might have heard some of the arguments around this increasingly controversial technique.
The final component is the notorious variability in cricoid pressure technique amongst staff performing it. A variety of pressures have been described with 30N being the current recommended amount. Whether this is the force applied, or even if this force is actually applied to cricoid cartilage rather than some other neck structure remains a recurring question.
So this leads to a position that I think is nicely reflected in the borrowed quote below:
'As a profession we invest a great deal of importance in a technique that is inadequately researched, poorly taught and badly performed' (Haslam & Duggan 2004)’
With that quite extensive preamble done I think it is time to turn to the article that was actually meant to be the focus of this post. Appearing in the March 2014 edition of Anesthesia and Analgesia you can get to the paper through the link below.
What's It About?
What Did They Find?
In terms of the other findings from the study the authors note from the video recordings that cricoid pressure did cause narrowing of the laryngeal opening and apposition of the cords in 30 of the patients, though there was no difficulty passing the ETT in any of these patients (sizes 7.0 and 7.5mm ID). The laryngeal opening was to the left side of the patient in respect to the glottis in 57% of the patients and in the midline in 32%, with no change in this position with cricoid pressure.
Is It Any Good?
There are some obvious limits to this study, most notably the fact that this is very much a surrogate for anything useful. The smallest gastric tube had an external diameter of 4mm but this still doesn’t tell us much about the effect on liquid stomach contents and their ability to regurgitate. Even though the 2 main operators were both blinded to each others actions, the authors report a visual difference of the oesophageal opening when cricoid pressure was applied that may have compromised the blinding for the operator passing the gastric tube. I also feel that the limitations applied to the patients involved in the study takes some of the edge of the applicability to real clinical practice, as these were all relatively slim, healthy patients without reflux symptoms. There were also a number of patient excluded (28 in total) due to the fact that visualisation of the oesophageal opening was a requirement to continue with the study. Though reasonable, it’s not quite clear to me whether there were any special characteristics of these patients which could have introduced bias, as little is said about them.
I don’t really like cricoid pressure. I personally find that it makes my job of airway management harder and this is something that is pretty widely recognised, and even hinted at in this study. And despite the careful attempts of the authors this is still just a study of a surrogate for regurgitation. However, protecting my patients and doing no harm is first on my priority list. This study doesn’t explicitly tell us that cricoid pressure works, but it does wriggle it’s eyebrows suggestively at you. Until there is solid data on outcome difference that I can see and feel confident with I will always end up erring towards what is probably safest for my patients, especially when the theory seems to make sense and it is still endorsed by many leading organisations. As pointed out in the Royal College of Anaesthetists'/Difficult Airway Society's 4th National Audit Project (NAP4) aspiration was the commonest cause of death reported. For now it looks like Sellick is still getting his way with us trainees. Damn!
Thanks for reading and, as always please let me know your thoughts on the topic. I know there is quite a bit of other evidence out there about that we will hopefully get round to looking at but let me know of any other links that have caught your eye. Until next time.
- PHARM - Pre Hospital and Retrieval Medicine reflect on cricoid pressure (they have also had a more recent look at this paper)
- Difficult Airway Society - The DAS Guidelines on RSI
- Best BETs - The Best BETs review of cricoid pressure
- NAP4 - The 4th National Audit Project has some interesting reading on aspiration and airway management
- Anesthesiology (2003) - Cricoid Pressure Displaces The Esophagus