ABSTRACT
Objective To assess the efficacy of recoil of inflating syringe plunger in limiting laryngeal mask airway (LMA) cuff pressure.Methods Sixty ASA Ⅰ or Ⅱ patients aged 22-64 yr with body mass index of 18-30 kg/m2 undergoing elective surgery under general anesthesia with LMA were enrolled in this study.LMA Supreme (Laryngeal Mask Co.Singapore) size # 3 (for patients with body weight ≤50 kg) or # 4 (for patients with body weight ＞ 50 kg) was placed after induction of anesthesia.Correct position of LMA was confirmed by fiberoptic bronchoscopy.The LMA cuff was inflated to 60,80,100 and 120 cm H2O step by step using a 20 ml-syringe.The cuff pressure was measured with a monometer through a 3-way stopcock and maintained at each level for 10 seconds.The plunger was then allowed to recoil.The cuff pressure at the end of recoil (residual cuff pressure) was recorded.The patients were mechanically ventilated.The inspiratory pressure was limited to 30 cm H2 O.The airway pressure at which the air started to leak between LMA and larynx (leak pressure-Pleak) was recorded.Results The residual cuff pressure following the 4 inflating pressures was all ＜ 60 cm H2 O.The Pleak was ＞20 cm H2O.There was no significant difference in residual cuff pressure and Pleak between size # 3 and # 4.Conclusion Recoil of inflating syringe plunger can limit LMA pressure to safe level.