The effect of cricoid and paralaryngeal force on upper oesophageal occlusion during induction of anaesthesia: a randomised, crossover study.

The aim of this study was to evaluate the effectiveness of cricoid and paralaryngeal force for oesophageal entrance occlusion during induction of anaesthesia. Seventy-four patients were included in this randomised, crossover study. The relative position of the glottis and outer anteroposterior diameter of the upper oesophageal entrance were assessed at baseline, after the application of 30 N cricoid and paralaryngeal force, and after induction of anaesthesia. The occlusion rate of the oesophageal entrance with cricoid and paralaryngeal force was assessed during direct laryngoscopy. The relative position of the upper oesophageal entrance to the glottis changed in 45 out of 74 patients after induction of anaesthesia and during direct laryngoscopy compared with the awake state. The application of cricoid and paralaryngeal force decreased the mean (SD) diameter of the upper oesophageal entrance to a similar degree in awake (8.5 (2.1) mm to 6.4 (1.7) mm and 6.5 (1.6) mm, respectively; p < 0.001) and anaesthetised (8.7 (2.2) mm to 6.5 (1.7) mm and (6.7 (1.9) mm, respectively; p < 0.001) states. During direct laryngoscopy, the occlusion rate of the oesophageal entrance was greater with cricoid compared with paralaryngeal force (46/74 vs. 26/74, respectively; p = 0.002). The relative position of the upper oesophageal entrance to the glottis may change after induction of anaesthesia and during direct laryngoscopy. Cricoid and paralaryngeal force both decrease the diameter of the upper oesophageal entrance in awake and anaesthetised states. Occlusion of the oesophageal entrance is achieved more frequently with cricoid force compared with paralaryngeal force during direct laryngoscopy.