Cricoid pressure: can protective force be sustained?

We studied six operating department assistants performing simulated cricoid pressure on a model of the larynx with the arm either flexed to 90 degrees (flexed position) or fully extended with the elbow locked (extended position). Subjects were asked to maintain forces of 20, 30 and 40 Newtons (N) for a target time of 20 min. Subjects rated pain during each assessment on a four-point verbal rating scale (VRS): 1 = uncomfortable; 2 = hurting; 3 = hurting a lot; and 4 = agony. Times to onset of pain were short and mean times to VRS 3 at each force studied were: 40 N, flexed position 2.3 min, extended position 5.4 min; 30 N, flexed position 4.0 min, extended position 7.5 min; and 20 N, flexed position 9.6 min, extended position 12.5 min. None of our subjects was able to sustain 40 N for the target time. Mean times to release at 40 N were: flexed position 3.7 min, extended position 7.6 min. Only one subject was able to sustain 30 N and then only using the extended arm. Mean times to release at 30 N were: flexed position 6.4 min, extended position (five subjects) 10.8 min. Two subjects with the arm flexed and five with the arm extended achieved the target time at 20 N. Mean times to release at 20 N were: flexed position (four subjects) 13.2 min, extended position (one subject) 14.6 min. Use of the extended arm consistently prolonged times to pain and fatigue. These findings are relevant to the management of cricoid pressure during failed intubation.