title: Time course of end-tidal desflurane concentration during delivery and elimination according to the type and location of filters in a semi-closed circuit system.
abstract: BACKGROUND
  The aim of this study was to determine whether the end-tidal concentration of desflurane would be affected by a breathing circuit system filter attached at two different positions in anesthetic breathing circuit systems.
  
  
  METHODS
  An artificial lung was ventilated under five different conditions. The first group was without any filter or desflurane (n = 5, sham), the second was with desflurane but without any filter (n = 10, control), the third group had a bacterial filter on the expiratory limb (n = 10), and the fourth and fifth groups had a viral/bacterial filter added on the expiratory limb (n = 10) or at the Y-piece of the breathing circuit (n = 10), respectively. In all groups except the sham, administration of 10% desflurane was performed for 5 minutes and then stopped for 5 minutes.
  
  
  RESULTS
  The mean (SD) end-tidal concentration of desflurane for the groups described above peaked at 0 (0), 9.8 (0.1), 9.8 (0.1), 8.5 (0.1), and 6.7% (0.1) (P < 0.001), respectively. There was no difference in the desflurane concentrations and the expired tidal volume over time between the control and bacterial group, but there was a significant difference between the control and the fourth and fifth groups (P < 0.001).
  
  
  CONCLUSIONS
  Filters can affect the expiratory desflurane concentration during anesthesia.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Kyung Hee University Hospital, Seoul, Korea.
authors.forename: Sung-Wook
authors.initials: SW
authors.lastname: Park
authors.affiliation: Department of Anesthesiology and Pain Medicine, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
authors.forename: Jun-Young
authors.initials: JY
authors.lastname: Chung
authors.affiliation: Department of Anesthesiology and Pain Medicine, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
authors.forename: Eun-Jin
authors.initials: EJ
authors.lastname: Moon
authors.affiliation: Department of Anesthesiology and Pain Medicine, Kyung Hee University Hospital, Seoul, Korea.
authors.forename: Young-Jin
authors.initials: YJ
authors.lastname: Kang
authors.affiliation: Department of Anesthesiology and Pain Medicine, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
authors.forename: Jong-Man
authors.initials: JM
authors.lastname: Kang
keywords: Concentration; Desflurane; Filter; Tidal volume