Table 2
Author, date,and countryPatient groupStudy type(level of evidence)OutcomesKey resultsStudy weaknesses
BVM, bag-valve-mask; RSI, rapid sequence intubation.
Sellick BA, 1961, UK26 high risk anaesthesia cases in which cricoid pressure was appliedObservational studyIncidence of reflux of gastric/oesophageal contents when cricoid pressure released post-intubation of tracheaIn 3 out of 26 cases release of cricoid pressure was followed by immediate reflux of gastric contents into pharynxObservational study in few patients. Study conducted in 1961 using anaesthetic techniques available at that time
Brimacombe JR and Berry AM, 1997, CanadaClinical and cadaver studiesMeta-analysisEvidence of aspirationNo high quality studies proving that cricoid pressure is beneficial in preventing aspirationNo search strategy given
Some studies report acid aspiration despite cricoid pressureNo inclusion criteria
Airway patencySome reports of cricoid pressure impeding airway patencyNo assessment of quality of studies
Upper oesophageal sphincter pressureSome evidence suggesting cricoid pressure increases upper oesophageal sphincter pressureVarious outcome measures used
Gastric insufflation with BVMSome evidence that cricoid pressure reduces gastric insufflation during BVMNo definitions for aspiration pneumonia given
Airway/soft tissue injuryCase reports of cricoid injury/soft tissue injury
Smith KJ et al, 2003, Canada22 healthy volunteersObservational study. MRI scans of necks were taken with and without the application of cricoid pressureOesophageal displacement laterally relative to the cricoid without cricoid pressure52.6% of casesHealthy awake volunteers were used, not paralysed patients undergoing RSI. Findings may be influenced by muscle tone and the swallowing reflex
Oesophageal displacement laterally relative to the cricoid with cricoid pressure90.5% of cases
Unopposed oesophagus without cricoid pressure.47.4% of cases
Unopposed oesophagus with cricoid pressure.71.4% of cases
Lateral laryngeal displacement66.7% of cases
Airway compression81% of cases