Which is better? BURP or bimanual? Is cricoid pressure of any use?
Sellick described cricoid pressure in 1961. How useful is it? Well it’s purpose is to minimise the passive movement of gastric contents into the oropharynx and the potential aspiration of those contents, during rapid sequence intubation. How good is it? I was recently asked this at an Airway Workshop and I had to say for what we have, it’s pretty good. BUT the evidence is not that great!
In fact some of the newer evidence now says, it may be detrimental and can affect intubation. It can further affect ventilation of the patient!
Initially the recommended pressure was 44Newtons which is equivalent to 4.5kg (10 pounds). At this pressure it was found that there was occlusion of the glottis in 50% of patients in one study (Anaesthesia 2000 march 263-268). To be fair, the conditions in this study, which was a small one (n=30) were somewhat artificial and not really reflecting the real scenarios.
In other studies where the effect of cricoid pressure on actually passing a tube through the cords was looked at. It was found that in a small number of cases, the cricoid pressure affected the ability to pass the tube (Anaesthesia 2007 May;62; 456-9). In those cases where the tube was getting stuck at the level of the glottis i.e. at the posterior cartilages, where usually a 90 degree rotation of the tube would relieve the issue, cricoid pressure made this more difficult.
In an MRI study looking at cricoid pressure, there was direct visualisation of the hypo-pharynx being occluded when cricoid pressure was applied (Anesth Analg 2009. Nov; 109;1546).
The correct use of cricoid pressure is of utmost importance, and the ability to use it to minimise the chance of aspiration remains to be tested. There is certainly evidence that it can make intubation far more difficult than no cricoid pressure being applied (J Emerg Med 2001 Jan 20;29-31) and if there is a difficulty in intubating then cricoid should be relaxed or even released.
There needs to be some idea of how much pressure needs to be used. There is no formal teaching in this area. The original 4.5kg of pressure is now not used and 2kg or 20N of pressure is recommended, but how do you guarantee this? How do you know how much pressure is being applied at any one time? When I’m tubing I ask for cricoid. How do I know if that cricoid is appropriate and if it’s affecting the intubation?
The BURP manoeuvre was established in 1993 by Knill and its purpose is to improve the view of the cords during laryngoscopy. People still get it wrong. It is the person intubating that is to apply this pressure, not someone else. The Backward,Upward to the Right Pressure must be applied to suit that person intubating.
In a study that compared the BURP technique with bimanual manipulation in cadavers (Ann Emerg Med 2006 Jun;47;548-55), it was found that bimanual manipulation improved the POGO (percentage of glottic opening) more than BURP or cricoid.
What is bimanual manipulation? It is simply putting external pressure on the thyroid cartilage and moving it whilst inserting the tip of the laryngoscope into the vallecula. The effect is that it assists the tip of the blade in reaching deeper into the vallecula and thus assists in elevating the epiglottis.
So a few things to remember here.
Be careful with cricoid pressure. There is a place for it in bag-valve mask as long as it is not too aggressive. It may however hinder intubation and even ventilation. So if you are encountering issues with intubation, or the patient is difficult to ventilate, release the cricoid and see if there is a resolution.
Cricoid plus BURP together may make intubation far more difficult.
Bimanual manipulation may be an effective technique.