Cricoid pressure and laryngoscopy

Randell et al. (Anaesthesia 1998; 53: 536–9) describe a modified cricoid pressure technique, employing pressure in a backward, upward and right direction, for improving the view at laryngoscopy, comparing it with levering the tip of a McCoy blade. A similar study was undertaken by Vanner et al. [1], who used cricoid pressure in an upward and backward direction only. It is worth noting that Knill [2], who originally proposed backward, upward and right-directed pressure to improve the view at laryngoscopy, himself emphasised that the pressure was applied to the thyroid rather than the cricoid cartilage. It is reasonable to suppose that directed pressure on the thyroid cartilage is more likely to achieve the desired end than jamming the cricoid against the cervical vertebrae. Furthermore, there is the possibility that the modified cricoid pressure will not achieve the second aim of obstructing the oesophagus. The ‘correct’ force of 30 N applied at an oblique angle will result in a lesser force in the backward direction, which might not be effective, especially if right-directed pressure is also applied.