A experimental model of a patient was designed to grade the success of ventilation using the Guedel airway/face mask (GA/FM), Laryngeal mask (LM) or Combitube (CT) in CPR. It consisted of a manikin head, training lung (Dräger®: compliance 50 ml/cmH2O, resistance 16 cmH2O/l/sec), lower esophagial sphincter pressure (LESP) 7 cmH2O and a simulated stomach [1]. Sixteen training nurses were shown the correct use of each device. The volunteers than used each device for a 2-min ventilation. For a successful ventilation a tidal lung volume of >200 mls had to be achieved within 180 s. Peak pressures in the esophagus, lung and gastric 2-min volumes were recorded. Each volunteer was graded from I (excellent) to 4 (bad), on the success of airway insertion, quality of the seal and visible adequacy of ventilation. The volunteers could deliver an adequate tidal lung volume with the GA/FM in 7-102 s (median: 24 s); LM in 18-92 s (median: 37 s), and 46-180 s (median: 74 s) with the CT. In the GA/FM group there were three failures, and two in the CT group. Analysis of the success of airway insertion, sealing and adequacy of ventilation shows a significant advantage with the LM or CT (P < 0.001) against the GA/FM. There was no difference between the LM and CT. The 2-min lung volume delivered with the GA/FM ranged from 4.2-13.41 (mean: 8.01), with peak LESP of 9-27 cmH2O (mean: 16.4 cmH2O) causing a gastric inflation of 2.5-13.61 (mean: 6.61). The 2-min lung volume with the LM was 11.7-4.1 l (mean: 251), peak LESP of 0-22 cmH2O (mean: 7.9 cmH2O) and gastric inflation of 0-6.21 (mean: 1.41). For the CT the 2-minute lung volume ranged from 12.3-41.51 (mean: 271), peak LESP of 0 and without gastric inflation. Our results show the significant risk of gastric distension when using the GA/FM. Adequate lung ventilation of > 5 l/min delivered with the GA/FM could be achieved only by 4 volunteers. The LM might provide the best alternative for airway management during CPR by nursing staff with a 100% success rate on adequacy of ventilation. A training program on the LM might further reduce the risk of gastric inflation.
References
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