Assessment of Positive Pressure Controlled Ventilation with the Laryngeal Mask Airway

Lim, Young Soon; Lee, Sang Kyi

Abstract

BACKGOUND: Cuff overinflation may cause premature rejection of the laryngeal mask airway (LMA) or provocation of incomplete and ineffective reflex responses. Therefore a previous report recommends that the cuff is inflated to a pressure of 60 cmH2O to minimize side effects. The objective of this study was to assess the possibility of controlled positive pressure ventilation in adults when intra-cuff pressure of LMA was set to 60 cmH2O.
METHODS
We studied 20 adult patients who received general inhalational anesthesia with LMA and mechanical positive pressure ventilation for gynecological operations. The following variables was determined during anesthesia at two time points 3 min after endotracheal intubation and 5 min before neuromuscular blockade: pop-off pressure, tidal volume, peak-air way pressure, plateau pressure, compliance, SpO2, and ETCO2.
RESULTS
Mean compliances measured were normal. Mean airway pressures (peak, plateau) were 13.6 and 15.1 cmH2O at two time points respectively while setting the tidal volume with 10 ml/kg. However, pop-off pressure were 18.3 and 20.1 cmH2O, respectively. Mean tidal volumes without gas leak around the LMA cuff were 14.5 and 14.5 ml/kg, respectively. Mean SpO2 and mean ETCO2 were measured 99.0 and 99.2%, 31.3 and 30.3 mmHg in two time points, respectively.
CONCLUSIONS
The study suggested that controlled mechanical positive pressure ventilation using the laryngeal mask airway with 60 cmH2O intra-cuff pressure were be adequate when pulmonary compliance and airway resistance were normal.