Comparison with current literature
The correct application of cricoid pressure is used to reduce the risk of aspiration during induction by compressing the oesophagus[1]. Importantly, despite all the study participants being clinically experienced in the application of cricoid pressure, 70% did not apply the correct pressure at baseline for either “awake” or “anaesthetised” patients. In particular, nearly half of all participants applied excessive force on the simulated “awake” patients which, clinically, can lead to pain and retching[9]. Moreover, the force applied to “anaesthetised” patients was less than recommended in the majority of participants. Ineffective pressure can increase the risk of aspiration[9]. Our results differ from previous studies which suggest that most assistants apply less cricoid pressure than is required during intubation[4,12–14]. There are several potential reasons for this including some studies using greater recommended force values for “anaesthetised” patients (>40 N versus >30 N in our study) [4,12], and differences in simulation airway models[13] and study populations (e.g. anaesthetic assistants versus medical specialists )[4,12–14].
Following teaching, the biofeedback and syringe teaching methods resulted in similar applied pressure (syringe method ~5N higher) in “anaesthetised” patients. This finding is not surprising since the model estimates for both methods fell very close to, if not inside, the recommended range of 30-40N. However, in “awake’ patients, the biofeedback method was more effective than the syringe method for teaching participants the required cricoid pressure force. The force applied using the syringe method was ~9N higher than the force applied using the biofeedback method. More importantly, the predicted syringe method force was higher than recommended for “awake” patients which, as noted above, can induce adverse clinical sequelae. Our findings differ to those of other studies which have reported that the syringe method leads to forces within the recommended range[8,20]; however, Flucker et al. trained and tested participants over a 1 month period which may contribute to the dissimilar findings [8]. Nonetheless, the results of our study confirm earlier reports that the biofeedback method is easy to teach and is the most effective technique for teaching the correct cricoid pressure[2,10,15–19].
Using the nose method to teach recommended pressure in “anaesthetised” patients yielded predicted cricoid pressure forces that were significantly lower (~9N) than those obtained using the biofeedback method. More importantly, the force applied was less than recommended which can lead to aspiration in patients undergoing intubation. [9]. Our findings are similar to the only other study that has assessed the nose method. The authors also reported this technique to be ineffective; albeit different force measurements were taken and target cricoid pressure forces for “anaesthetised” patients were 25-35 N, not the 30-40 N target pressure used in our study[7].