Comparison of cuffed, uncuffed tracheal tubes and laryngeal mask airways in low flow pressure controlled ventilation in children

Background: The 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. Methods: Following 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. Results: The 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. Conclusions: We 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.