Using the inflating syringe as a safety valve to limit laryngeal mask airway cuff pressure

Hyperinflation of the laryngeal mask airway (LMA) cuff is thought to be the etiology underlying many of the complications associated with the use of this device. Until now, there has not been a clinically acceptable method (besides direct measurement) to assure that the cuff pressure is maintained less than the recommended maximum value of 44 mm Hg (60 cm H(2)O).

We inflated sizes #2 and #5 LMAs with air to 40, 60, or 120 mm Hg starting pressures, using 30- and 60-ml BD™ and B Braun™ syringes; we then allowed the syringe plungers to recoil to equilibrium before removing the syringe from the LMA inflation port. Residual LMA cuff pressures following complete passive recoil were measured and recorded.

A number of combinations of syringes (30 and 60 ml) and starting pressures (40, 60, 120 mm Hg) resulted in safe residual (#2 and #5 LMA) cuff pressures of <44 mm Hg.

When using specific combinations of syringes, LMA sizes and inflation pressures, these data demonstrate an efficient, practical and easy method to achieve an initial equilibrium recoil LMA cuff pressure that is less than, or very near to, the recommended upper safe limit of 44 mm Hg.