Table 2

Author, date and countryPatient groupStudy type (level of evidence)OutcomesKey resultsStudy weaknesses
Benumof JL, 1996, USA181 elective patients undergoing GA.Back plus cephalad pressure was compared with standard viewObservational studyImprovement of laryngoscopic viewAll views improved
Number of improved views in grade 3 groupAll views improved
Takahata O, 1997, Japan630 patients undergoing routine surgery.BURP was compared with back pressure on the larynxObservational studyNumber of improved views in grade 3 group357 grade 1 views, 261 grade 2 views,12 grade 3 views, 0 grade 4 views. 9 patients with an initial grade 3 Cormack view improved to grade 2 after simple back pressure.Comparison was with back pressure on thyroid cartiladge rather than on cricoid.Very small number of initial grade 3, and no grade 4 views.
Number of improved views in grade 3 groupAll patients with an initial grade 3 Cormack score improved to grade 2 after BURP.
Number of grade 2 views that improved (to grade 1 or an improved grade 2)176/261 after back pressure alone. 42/85 further improved with BURP
Vanner RG, 1997, UK55 elective female patients standard view v simple cricoid v cricoid plus upward pressureObservational studyNumber of improved views with upward pressure v simple cricoid aloneBetter with upward pressureOnly female patients