Comparison of cuff-pressure changes in silicone and PVC laryngeal masks during nitrous oxide anaesthesia in spontaneously breathing children

Background
The purpose of this study was to evaluate the cuff pressures of four different laryngeal masks in paediatric patients undergoing routine surgery and to determine whether there is a substantial increase in cuff pressure when silicone masks are used compared to PVC laryngeal mask airways.

Methods
Hundred and forty patients aged < 16 yr were randomly allocated to receive one of four extraglottic airway devices: LMA-Classic; LMA-Unique; Soft Seal; or Cobra-PLA. Intracuff pressure was monitored continuously throughout the operative intervention. The primary outcome was measurement of an increase in cuff pressure. First attempt success rate, effective airway time, anatomical position of the airway and incidence of airway morbidity data were monitored.

Results
Mean cuff pressure increased within 5 min of N2O exposure, and was substantially higher in the silicone LMA-C, compared to the PVC-based extraglottic airway devices tested, reaching a plateau of the cuff pressure after 45 min. The overall first attempt success rate (97%) and the mean effective airway time (24 ± 9 sec) were very satisfactory and all patients underwent successful surgery. Anatomical position was adequate in most airways, although in 34% of the patients in the Cobra group herniation of either the epiglottis or arytenoids were detected. Airway morbidity due to the devices was insignificant.

Conclusions
This study demonstrated a substantial increase in cuff pressure during anaesthesia for children in whom a silicone-based LMA-C was used, whereas PVC-based extraglottic airway devices showed a much lower increase.