Background and Goal of Study:

LMA Protector™  is the newest generation laryngeal mask airway. LMA Protector has a dual gastric drainage channel. Airway tube and cuff are 100% silicone and there are no aperture bars. Silicone cuffs have shown to reduce risk of sore throat and achieve higher seal pressures. The tube of LMA protector is more flexible. An integrated cuff pressure indicator enables continuous cuff pressure monitoring. The cuff of LMA Supreme  is polivinylchloride, has one gastric drainage channel and has aperture bars. The tube is more rigid. The primary hypothesis is: the oropharyngeal leak pressure of the LMA Protector is 5 cm H20 higher than the oropharyngeal  leak pressure of the LMA Supreme. Secondary outcome measures are: ease of insertion, fibreoptic position, ease of gastric tube placement and complications.

Materials and Methods:

ASA I, II or III, outpatients planned for minor surgery, aged 19-71 years, were recruited after informed consent and were randomized in an LMA Supreme (15 patients) or Protector group (17 patients)(recruitment incomplete). The insertion technique for both LMA types included neck flexion and head extension and full deflation of the cuff.  The expiratory valve of the ventilator was closed and fresh gas flow was set at 3 l/min. Oropharyngeal leak pressure was determined at 0, 10, 20, 30 and 40 ml cuff volume, when an audible noise was detected at the mouth. The corresponding airway pressure was measured using an digital manometer. Finally cuff pressure was set at 65 cmH20 using a manual cuff pressure monitor and the  corresponding leak pressure was again measured. Subsequently patients lungs were ventilated at a tidal volume of 10ml/kg at a respiratory rate of 12/min. 

Results and Discussion:

At the different cuff volumes, the leak pressure was significantly higher for the LMA Protector compared to the LMA Supreme. Mean leak pressure (cmH20) (SD) at 0 ml cuff volume was 18 (7) for LMA Protector vs 9 (5) for LMA Supreme. Leak pressure at 10,20,30,40 ml cuff volumes are 24(9) vs 13(3) and 30(10) vs 19(5) and 30(9) vs 22(7) and 32(8) vs 24(8), respectively for LMA Protector vs LMA Supreme. At cuff pressure of 65 cmH20 leak pressures are 30(9) vs 21(6).

Conclusion(s):

At different cuff volumes, oropharyngeal leak pressures are consistently higher (> 5 cm H20) for LMA Protector vs LMA Supreme. LMA Protector therefore allows effective ventilation at higher airway pressures than LMA Supreme.

11 / A randomized study comparing the Laryngeal Mask Airway Supreme with the Laryngeal Mask Airway Protector in the ambulatory surgery unit.