• Thomas Engelhardt, Graham Johnston, and Manisha M Kumar.
• Department of Anaesthesia and Intensive Care, Royal Aberdeen Children's Hospital, Aberdeen, UK. t.engelhardt@abdn.ac.uk
• Paediatr Anaesth. 2006 Feb 1;16(2):140-3.

BackgroundThe use of low flow circle systems necessitates a 'leak free' breathing system which is commonly achieved by using a cuffed tracheal tube (TT). We hypothesized that low flow circle system anesthesia can equally effectively be achieved by using the LMA in pediatric anesthesia.MethodsFollowing local ethics committee approval we randomly recruited 45 patients scheduled for elective surgery and requiring mechanical ventilation into three groups (cuffed TT, uncuffed TT and LMA group, n = 15). The size of the TT was determined by means of the formula (age/4) + 4.5 for uncuffed and (age/4) + 4 for cuffed TT whereas the size of the LMA size was dependent on weight. Following induction of anesthesia and muscle paralysis patients were ventilated with pressure controlled ventilation through a pediatric circle system and the lowest fresh gas flow (FGF) determined.ResultsThe FGF achieved were (median and range) 0.20 (0.2-0.25) l.min(-1) for the LMA group, 0.20 (0.2-0.4) l.min(-1) for the cuffed TT group and 1.15 (0.2-4.75) l.min(-1) for the uncuffed group. The differences between the LMA and cuffed TT compared with the uncuffed TT were significant (P < 0.0001 and P = 0.0002, respectively). The difference in FGF between LMA and cuffed TT was not significant.ConclusionWe conclude that pressure controlled ventilation using an LMA is an alternative to a cuffed TT during low flow circle system anesthesia in children. Low FGF is unlikely to be achieved consistently using an uncuffed TT because of a substantial leak.

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