title: The effect of fresh gas flow rate and type of anesthesia machine on time to reach target sevoflurane concentration.
abstract: Anesthesia machines have been developed by the application of new technology for rapid and easier control of anesthetic concentration. In this study, we used a test lung to investigate whether the time taken to reach the target sevoflurane concentration varies with the rate of fresh gas flow (FGF) and type of anesthesia machine (AM).
  
  
  
  We measured the times taken to reach the target sevoflurane concentration (2 minimum alveolar concentration = 4%) at variable rates of FGF (0.5, 1, or 3 L/min) and different types of AM (Primus®, Perseus®, and Zeus®[Zeus®-F; Zeus®fresh gas mode, Zeus®-A; Zeus®auto-mode]). Concomitant ventilation was supplied using 100% O2.The AMs were connected to a test lung. A sevoflurane vaporizer setting of 6% was used in Primus®, Perseus®, and Zeus®-F; a target end-tidal setting of 4% was used in Zeus®-A (from a vaporizer setting of 0%). The time taken to reach the target concentration was measured in every group.
  
  
  
  When the same AM was used (Primus®, Perseus®, or Zeus®-F), the times to target concentration shortened as the FGF rate increased (P < 0.05). Conversely, when the same FGF rate was used, but with different AMs, the time to target concentration was shortest in Perseus®, followed by Primus®, and finally by Zeus®-F (P < 0.05). With regards to both modes of Zeus®, at FGF rates of 0.5 and 1 L/min, the time to target concentration was shorter in Zeus®-A than in Zeus®-F; however, the time was longer in Zeus®-A than in Zeus®-F at FGF rate of 3 L/min (P < 0.05).
  
  
  
  Shorter times taken to reach the target concentration were associated with high FGF rates, smaller internal volume of the AM, proximity of the fresh gas inlets to patients, absence of a decoupling system, and use of blower-driven ventilators in AM.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University Anam Hospital, College of Medicine, Korea University, Inchon-ro 73, Seongbuk-gu, 02841, Seoul, Republic of Korea. drhwshin@naver.com.
authors.forename: Hye Won
authors.identifier: 0000-0003-3770-6675
authors.initials: HW
authors.lastname: Shin
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University Anam Hospital, College of Medicine, Korea University, Inchon-ro 73, Seongbuk-gu, 02841, Seoul, Republic of Korea.
authors.forename: Hae Na
authors.initials: HN
authors.lastname: Yu
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University Anam Hospital, College of Medicine, Korea University, Inchon-ro 73, Seongbuk-gu, 02841, Seoul, Republic of Korea.
authors.forename: Go Eun
authors.initials: GE
authors.lastname: Bae
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University Anam Hospital, College of Medicine, Korea University, Inchon-ro 73, Seongbuk-gu, 02841, Seoul, Republic of Korea.
authors.forename: Hyub
authors.initials: H
authors.lastname: Huh
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University Anam Hospital, College of Medicine, Korea University, Inchon-ro 73, Seongbuk-gu, 02841, Seoul, Republic of Korea.
authors.forename: Ji Yong
authors.initials: JY
authors.lastname: Park
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University Anam Hospital, College of Medicine, Korea University, Inchon-ro 73, Seongbuk-gu, 02841, Seoul, Republic of Korea.
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Kim
mesh_terms: D000769:Anesthesia, Inhalation / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D066298:In Vitro Techniques; D008168:Lung / Q000378:metabolism*; D008738:Methyl Ethers / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000077149:Sevoflurane; D013997:Time Factors
chemical_list: D008738:Methyl Ethers; D000077149:Sevoflurane
keywords: Equipment design; Inhalation anesthetics; Ventilation