• Yuri Nakae, Dai Horikawa, Keiko Tamiya, and Akiyoshi Namiki.
• Department of Anesthesia, Hokkaido Children's Medical Center, 1-10-1 Zenibako, 047-0261, Otaru, Japan.
• J Anesth. 1998 Dec 1; 12 (4): 175-179.

PurposeThe aim of this study was to compare the effect of low-flow anesthesia with or without a heat and moisture exchanger with high-flow anesthesia on airway gas humidification in children.MethodsOne hundred twenty children were randomly assigned to one of three groups: low-flow anesthesia with 0.5l·min-1 of total gas flow (LFA,n=40), low-flow anesthesia with 0.5l·min-1 using a heat and moisture exchanger (HME,n=40), and high-flow anesthesia with 6l·min-1 (HFA,n=40). The temperature and relative humidity of the inspired gas were measured throughout anesthesia.ResultsThe relative humidity of the inspired gas in the HME group was increased compared with that of the LFA and HFA groups 20 min after induction (p<0.05). The airway humidification in the LFA group was higher than that in the HFA group 10 min after induction (p<0.05). The temperature of the inspired gas in the HME group was increased compared with that in the LFA and HFA groups after 70 min (P<0.05).ConclusionLow-flow anesthesia is less effective in providing adequate humidification of inspired gas than low-flow anesthesia with a heat and moisture exchanger, but significantly better than high-flow anesthesia in children.

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