SummaryThe efficacy of cricoid pressure was studied in 10

SummaryUpper oesophageal sphincter pressure has been measured in 24 patients with a sleeve device. The median sphincter pressure when awake was 38 mmHg. and when anaesthetised and paralysed was 6 mmHg. Afier tracheal intubation, cricoid pressure was applied at measured values between 5 and 50 N using a hand-held cricoid yoke while the sphincter pressure was recorded in two head and neck positions: with and without a standard intubating pillow with neck support. A cricoid ,force of 40 N increased sphincter pressure to above 38 mmHg in all the patients and the use of'the pillow did not alter this effect. With the application of' cricoid pressure, operating department assistants raised sphincter pressure to above 38 mmHg in only 50% of patients. Laryngoscopy made little dijerencp to the effect of cricoid pressure except in one patient in whom it reduced the sphincter pressure by 27 mmHg.

SummaryThe upper oesophageal sphincter can prevent regurgitation of oesophageal contents into the pharynx following gastrooesophageal rejux in the awake patient. Upper oesophageal sphincter pressure was recorded with a Dent sleeve after hypnosis with midazolam (n = 7 ) and also during the rapid intravenous induction of anaesthesia with thiopentone ( n = 16) or ketamine (n = 7 ) . Thiopentone decreased mean(SD) sphincter pressure from an awake value of 43(19) to 9 ( 7 ) mmHg ( p < 0.001) and midazolam from 38(25) to 7 ( 3 ) mmHg ( p < 0.02). Mean(SD) sphincter pressures before and after ketamine were not significantly diflerent at 29( I S ) and 32(2I) mmHg respectively. After suxamethonium mean( S D ) sphincter pressure in all patients (n = 30) was 7 ( 4 ) mmHg. Laryngoscopy (n = 30) caused a small increase in meanlSD) sphincter pressure to 13(10) mmHg ( p < 0,001). Thiopentone caused a rapid fall in upper oesophageal sphincter pressure which usually started before loss of consciousness. These findings have implications for the timing of cricoid pressure application.