The cricoid debate – balancing risks and benefits

The interesting, well-constructed letters by Professor Priebe [1] and Dr. Mushambi [2] reignite the debate on the value of cricoid force during rapid sequence induction (RSI). While the focus is on the obstetric guidelines, the argument extends to the recently published Difficult Airway Society 2015 guidelines [3] and will be relevant for the guidelines for managing difficult intubation in the critically ill, which are in preparation. This is not a new debate, as the excellent 1999 editorial by Vanner and Asai illustrates [4], but the step changes that have occurred in airway management in the last decade do inform it. It is perhaps worth reflecting on the findings of NAP4, which reported that aspiration remains the commonest cause of airway-related death and brain damage [5]. A substantial number of these cases involved patients in whom RSI would traditionally have been performed or in whom there were concerns over the practice of RSI [6]. It is therefore beholden on us as a community to do all we can to reduce these (rare) events. NAP4 did not receive any reports of major morbidity related to complications of the application of cricoid force and the NAP4 review team judged that, on balance, cricoid force should be retained as a component of RSI. I agree with Dr. Mushambi that the call for a randomised controlled trail (RCT) of cricoid force will not happen. If planned in high-risk patients it would likely be rejected on ethical grounds, and if planned in low-risk patients the study would be too large – likely hundreds of thousands of patients to be practical. Not all interventions are evaluable by RCTs and in those circumstances we rely on logic and the available indirect evidence: whether parachutes reduce mortality when jumping from a plane is an oft-quoted example [7]. My reading of the evidence (which there is no space to describe in a letter) and my practical experience is that correctly applied cricoid force does not: i) worsen the view at laryngoscopy; or ii) significantly interfere with mask ventilation. The challenge is therefore to ensure that cricoid force is correctly applied. Those who apply cricoid force should be trained in the technique and this is also recommended in the NAP4 report [5]. Once trained, assistants can rehearse the required force (immediately before induction) by depressing a capped air-filled syringe (e.g. most 20 ml syringes from 20 to 12 ml and most 50 ml syringes from 50 to 32ml) and this improves the reliability of the force applied [8]. It is a simple, effective intervention to improve the reliability and safety of the technique. Two additional points are relevant. The increasing availability of videolaryngoscopy changes the dynamic of intubation and when a remote screen is used, all those participating in the intubation (e.g. intubator, assistant, trainer) can observe a wide-angle view of the larynx and any difficulties. Videolaryngoscopy enables the operator and assistant to directly observe the effect of cricoid force or attempts at laryngeal manipulation. This is, in practice, a significant benefit and reinforces the (direct) view that cricoid force is a benign procedure. There is an increasing argument that videolaryngoscopy with a remote screen should be used for all RSIs.