This involves digital pressure against the cricoid cartilage of the larynx, pushing it backwards. The oesophagus is thus compressed between the posterior aspect of the cricoid and the vertebrae behind. The cricoid is used because it forms the only complete ring of the larynx and trachea.
The cricoid is located at the level of C6. Moderate pressure may be applied before loss of consciousness, and firmer pressure maintained until the cuff of the tracheal tube is inflated.
Estimates of the force required vary from 20 N to over 40 N. It must be released during active vomiting, to reduce the risk of oesophageal rupture.
Brian A Sellick 1918-1996, Anaesthetist, London, UK.
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