Asai T, Barclay K, McBeth C, Vaughan R S
Department of Anaesthetics and Intensive Care Medicine, University of Wales College of Medicine, Cardiff.
Br J Anaesth. 1996 Jun;76(6):772-6. doi: 10.1093/bja/76.6.772.
We studied 50 patients, in a blind, crossover study, to assess if cricoid pressure applied after placement of the laryngeal mask prevented gastric insufflation without affecting ventilation. After induction of anaesthesia and neuromuscular block, a laryngeal mask was inserted and confirmed to be placed correctly. The lungs were ventilated with a maximum inflation pressure of 15 cm H2O. In the first 25 patients, expiratory volumes were measured with and without cricoid pressure (30 N). On both occasions, a free hand was placed under the patient's neck. In the next 25 patients, the effect of cricoid pressure on ventilation without support of the neck was also studied. The effect of cricoid pressure with support of the neck on gastric insufflation was then assessed using a stethoscope in all 50 patients, while the lungs were ventilated with a maximum inflation pressure of 30 cm H2O. At the end of the study, the position of the mask was re-assessed. Cricoid pressure significantly decreased mean expiratory volume (P << 0.001). This inhibitory effect was significantly greater when the pressure was applied without support of the neck (P << 0.001). Cricoid pressure significantly reduced the incidence of gastric insufflation (12 patients vs one patient; P << 0.001; 95% CI for difference 10.5-33.5%). In no patient was the mask dislodged after these procedures. Thus, although cricoid pressure applied after insertion of the laryngeal mask prevented gastric insufflation, it also decreased ventilation. The inhibitory effect of cricoid pressure on ventilation without support of the neck was greater than cricoid pressure with support of the neck.
我们在一项双盲交叉研究中对50例患者进行了研究，以评估在置入喉罩后施加环状软骨压迫是否能防止胃内充气且不影响通气。麻醉诱导和神经肌肉阻滞之后，插入喉罩并确认位置正确。使用最大充气压力为15 cm H₂O进行肺通气。在前25例患者中，分别在施加和不施加环状软骨压迫（30 N）的情况下测量呼气量。两种情况下，均有一只手放在患者颈部下方。在接下来的25例患者中，还研究了在不托颈的情况下环状软骨压迫对通气的影响。然后，在所有50例患者肺通气最大充气压力为30 cm H₂O时，使用听诊器评估托颈情况下环状软骨压迫对胃内充气的影响。研究结束时，重新评估喉罩位置。环状软骨压迫显著降低了平均呼气量（P << 0.001）。在不托颈施加压力时，这种抑制作用显著更大（P << 0.001）。环状软骨压迫显著降低了胃内充气的发生率（12例患者 vs 1例患者；P << 0.001；差异的95%置信区间为10.5 - 33.5%）。在这些操作后，没有患者的喉罩移位。因此，尽管在置入喉罩后施加环状软骨压迫可防止胃内充气，但它也会降低通气。环状软骨压迫在不托颈时对通气的抑制作用大于托颈时。
