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].