Saline as an alternative to air for filling the laryngeal mask airway cuff

We have assessed a new method to evacuate saline completely from the laryngeal mask airway (LMA) cuff and tested the hypothesis that intracuff pressures, fibreoptic position and oropharyngeal leak pressures are similar for saline compared with air during nitrous oxide-oxygen anaesthesia. Eight size 4 LMA were inflated with saline 30 ml. After syringe evacuation, median residual weight was 0.56 (range 0.24-0.98) g; after additional manual cuff squeezing it was 0.26 (0.21-0.35) g; and after drying for 12 h at 60 degrees C with the valve open it was -0.02 (-0.05-0.04) g. Pressure-volume curves of four size 3-5 LMA showed that compliance was lower for the saline-filled cuff. A clinical study of 20 patients allocated randomly to have saline or air in the cuff showed a significant increase in intracuff pressure with air, but not saline, during nitrous oxide-oxygen anaesthesia. The fibreoptic position of the LMA changed more frequently in the air, compared with the saline-filled group (four of 10 vs none of 10; P=0.04). Oropharyngeal leak pressures were similar between groups. We conclude that the saline-inflated LMA cuff was reliably emptied and more stable in terms of intracuff pressures and possibly fibreoptic position. Filling the LMA cuff with saline is a viable option during laser surgery to the airway.