Effect of cricoid pressure on insertion of and ventilation through the cuffed oropharyngeal airway

We have assessed the effect of cricoid pressure on insertion of and ventilation through the cuffed oropharyngeal airway (COPA) in 53 patients, in a double-blind, randomized study. Two anaesthetists assessed adequacy of ventilation in anaesthetized and paralysed patients at the same time but using different methods. The first assessed ventilation clinically, by observing synchronized chest expansion with gentle manual ventilation and the second noted measurements of tidal volume (VT) and peak inspiratory pressure (PIP). Five mask ventilated breaths ('baseline') were assessed as above. Patients were then allocated randomly to receive cricoid pressure (group A, n=28) or no cricoid pressure (group B, n=25). Five further mask ventilated breaths ('after manoeuvre') were again assessed. A COPA was then inserted and five further breaths ('after COPA') were assessed. A COPA was inserted at the first attempt in all patients except for one in group A who required two attempts. COPA placement was difficult in one patient in group B who had a small distance between the incisor teeth. Ventilation was clinically 'adequate' in all patients except for one in the cricoid pressure group. There were no significant differences in measured VT or PIP between 'baseline' and 'after manoeuvre' breaths. Significant differences in VT and PIP were found after COPA insertion in the group that received cricoid pressure, with a mean decrease in VT of 108 mi (P=0.0049) and a mean increase in PIP of 5.2 cm H2O (P=0.0111).