| Objective:To assess the efficacy of recoil of inflating syringe plunger in limiting laryngeal mask airway Supreme (LMA Supreme) cuff pressure.Methods:(1) Sixty ASA I or II patients, aged 22-64yr, with body mass index (BMI) of 18～30 kg/m2, weighing 30～70 kg (30～50 kg for thirty and 51-70 kg for thirty) undergoing elective surgery under general anesthesia with LMA Supreme were enrolled in this study.(2) After induction of anesthesia, 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 while the bispectral index (BIS)was less than 60 and the first twitch(T1) was 0. After the correct position of LMA was confirmed by fiberoptic bronchoscopy, mechanical ventilation was performed with the cuff pressure at 35 cm H2O.(3) The LMA Supreme cuff was inflated to 60,80,100 and 120 cm H20 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. When the syringe plunger reached complete equilibrium, the cuff pressure at the end of recoil (residual cuff pressure) was recorded.(4) The patients were manually ventilated. The inspiratory pressure was limited to 30 cm H2O. The airway pressure at which the air started to leak between LMA and larynx (leak pressure-Pleak) was recorded.Results:(1) Starting cuff pressure at 60,80,100 and 120 cm H20, when the 20 ml-syringe plunger recoiled to complete equilibrium, the 95% confidence interval (CI) of corresponding residual cuff pressure of size #3 LMA Supreme was less than 60 cm H20.(2) Starting cuff pressure at 60,80,100 and 120 cm H20, when the 20 ml-syringe plunger recoiled to complete equilibrium, the 95% CI of corresponding Pieak of size #3 LMA Supreme was more than 20 cm H20.(3) Starting cuff pressure at 60,80,100 and 120 cm H20, when the 20 ml-syringe plunger recoiled to complete equilibrium, the 95% CI of corresponding residual cuff pressure of size #4 LMA Supreme was less than 60 cm H20.(4) Starting cuff pressure at 60,80,100 and 120 cm H20, when the 20 ml-syringe plunger recoiled to complete equilibrium, the 95% CI of corresponding Pieak of size #4 LMA Supreme was more than 20 cm H20.(5) Used the 20 ml-syringe plunger as the safty valve, there was no significant difference in residual cuff pressure between size # 3 and size #4 LMA Supreme (P>0.05)(6) When the patients were mechanically ventilated by LMA Supreme with the residual cuff pressure, there was no significant difference in Pleak between size #3 and size #4 (P>0.05)Conclusion:(1) Recoil of 20 ml-syringe plunger can be an efficient method to limit LMA Supreme to safe level.(2) Used the 20 ml-syringe plunger as the safty valve, the patient can achieve satisfactory Pleak during the ventilation by LMA Supreme.(3) When the cuff pressure can’t be accurately measured, the recoil of 20 ml-syringe plunger can be simply and efficiently used for LMA Supreme ventilation.Objective:To draw the pressure volume curves of laryngeal mask airways Supreme (LMA Supreme), and to provide reference for avoiding that the cuff pressure is exceeded the recommended maximum value of 60 cm H20.Methods:(1) In an in vitro set up.fifteen size #3, size #4, size #5 were used in this study, respectively.(2) Every LMA Supreme cuff was inflated by a 10-ml syringe via a three way tap attached between the pilot cuff and a hand held manometer.(3) Every LMA Supreme cuff was inflated with 1-ml increments of air from resting cuff volume (defined as volume of air in the LMA cuff at atmospheric pressure with the pilot balloon valve opened to ambient pressure). The corresponding pressure had been noted until the cuff pressure exceeded 120 cm H20.Results:(1) Starting with resting cuff volume, when the filling volume reached a quarter of the maximum recommended volume, the cuff pressure would exceed 60 cm H2O for all the three types of LMA Supreme.(2) Starting with resting cuff volume, when the filling volume reached half the maximum recommended volume, the air would produce a cuff pressure more than 120 cm H20.Conclusion:(1) For all the three types of LMA Supreme, when the filling volume for the cuff reached its maximum recommended volume, the cuff would reach its maximum recommended pressure.(2) Smaller cuff volume changes can result in larger cuff pressure, consequently, the cuffs should be inflated with the minimum volume of air required to form an effective seal with the respiratory tract. |
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