Forty children were randomly allocated into 4 groups according to the ventilation of their lungs by a circle breathing system in a Drger Primus anesthesia workstation with low ( 1 Lmin ) or high ( 3 Lmin ) FGF without an HME ( 1L and 3L groups ) or with an HME ( Pall BB25FS , Pall Biomedical , East Hills , NY ; HME1L and HME3L groups ) .