The effect of single-handed cricoid pressure on neck movement after applying manual in-line stabilisation

In 30 ASA 1 and 2 patients undergoing general anaesthesia and neuromuscular paralysis, manual in-line stabilisation of the neck in a neutral position was performed and single-handed cricoid pressure was applied. Vertical displacement was measured from the midpoint of the neck (directly below the cricoid cartilage). Measurements were also made at the tragus of the ear and the shoulder; both of which acted as fixed reference points. Mean neck displacement was 4.6 mm with a range of 0-8 mm. Mean tragus and shoulder displacements were 0.5 mm and 0.9mm, respectively, with a range of 0-2 mm at each point. Vertical displacement was also measured in 10 patients from a stylet fixed to the posterior aspect of the neck. Mean displacement measured at this point was 5.0 mm with a range of 2-9 mm. Single-handed cricoid pressure caused vertical displacement of the neck of between 4.6 and 5 mm with a range of 0-9 mm. Only some of this movement, i.e. 0.5-0.9 mm (range 0-2mm) can be accounted for by displacement of the whole patient as determined from measurements at the two fixed reference points. These findings have implications for emergency management of the airway in trauma patients.