Laryngeal mask airways--to inflate or to deflate after insertion?

Hyperinflation of the laryngeal mask airway (LMA) cuff is known to be a risk factor for airway morbidity and increased leakage around the LMA. While the manufacturers' recommendation is to inflate the cuff with the maximum recommended volumes and/or to adjust the cuff pressure to <60 cmH2O, cuff pressures below 40 cmH2O have been shown to be associated with a minimal rate of sore throat and minimal leakage. However, it remains to be determined whether inflation or deflation is needed to achieve favorable pressures. Therefore, we assessed the need for cuff-volume adjustment following insertion of the LMA unchanged straight from the sterile packaging in a prospective audit.

One thousand children (0-16 years) undergoing elective surgery were consecutively included in this quality of care audit. After taking the LMA from its sterile packaging, the LMA cuff was emptied and the amount of air recorded. Then, the same amount of air was returned into the LMA, the LMA was inserted into the patient, and the cuff pressure was measured using a calibrated cuff manometer.

Following insertion of the LMA (without further inflation or deflation of the cuff), 20.5% of children had cuff pressures > or = 60 cmH2, while 55.7% had LMA cuff pressures <40 cmH2O. Cuff pressures were also significantly higher in size 1 LMAs (66.6% had cuff pressures > or = 60 cmH2O and 2% <40 cmH2O) compared with all other sizes (P < 0.05). Furthermore, cuff pressures in LMAs with a poly vinyl chloride (PVC) surface were higher compared to LMAs with a silicone surface (65.2% > or = 60 cmH2O and 9.3% <40 cmH2O vs 9% > or = 60 cmH2O and 67.6% <40 cmH2O, respectively).

This study demonstrates that LMAs, particularly when using small-sized LMAs or LMAs with a more rigid PVC surface, need to be deflated following insertion of the device rather than inflated to avoid cuff hyperinflation. Hence, cuff pressures should be measured routinely using a manometer to minimize potential pressure-related airway complications.