title: Evaluating the efficiency of desflurane reflection in two commercially available reflectors.
abstract: With the AnaConDa™ and the MIRUS™ system, volatile anesthetics can be administered for inhalation sedation in intensive care units. Instead of a circle system, both devices use anesthetic reflectors to save on the anesthetic agent. We studied the efficiency of desflurane reflection with both devices using different tidal volumes (VT), respiratory rates (RR), and 'patient' concentrations (CPat) in a bench study. A test lung was ventilated with four settings (volume control, RR × VT: 10 × 300 mL, 10 × 500 mL, 20 × 500 mL, 10 × 1000 mL). Two different methods for determination of reflection efficiency were established: First (steady state), a bypass flow carried desflurane into the test lung (flowin), the input concentration (Cin) was varied (1-17 vol%), and the same flow (flowex, Cex) was suctioned from the test lung. After equilibration, CPatwas stored online and averaged; efficiency [%] was calculated [Formula: see text]. Second (washout), flowinand flowexwere stopped, the decline of CPatwas measured; efficiency was calculated from the decay constant of the exponential regression equation. Both measurement methods yielded similar results (Bland-Altman: bias: -0.9 %, accuracy: ±5.55 %). Efficiencies higher than 80 % (>80 % of molecules exhaled are reflected) could be demonstrated in the clinical range of CPatand VT. Efficiency inversely correlates with the product of CPatand VTwhich can be imagined as the volume of anesthetic vapor exhaled by the patient in one breath, but not with the respiratory frequency. Efficiency of the AnaConDa™ was higher for each setting compared with the MIRUS™. Desflurane is reflected by both reflectors with efficiencies high enough for clinical use.
authors.affiliation: Department of Anesthesiology, Intensive Care Medicine and Pain Medicine Saarland University Medical Center, University of Saarland, Kirrbergerstrasse 1, 66421, Homburg/Saar, Germany. hagen.bomberg@uniklinikum-saarland.de.
authors.forename: Hagen
authors.initials: H
authors.lastname: Bomberg
authors.affiliation: Department of Anesthesiology, Intensive Care Medicine and Pain Medicine Saarland University Medical Center, University of Saarland, Kirrbergerstrasse 1, 66421, Homburg/Saar, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Wessendorf
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, St. Josef Hospital, Katholisches Klinikum, University Hospital, Bochum, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bellgardt
authors.affiliation: Department of Anesthesiology, Intensive Care Medicine and Pain Medicine Saarland University Medical Center, University of Saarland, Kirrbergerstrasse 1, 66421, Homburg/Saar, Germany.
authors.forename: Max
authors.initials: M
authors.lastname: Veddeler
authors.affiliation: Institute for Medical Biometry, Epidemiology and Medical Informatics, Saarland University, Campus Homburg/Saar, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Wagenpfeil
authors.affiliation: Department of Anesthesiology, Intensive Care Medicine and Pain Medicine Saarland University Medical Center, University of Saarland, Kirrbergerstrasse 1, 66421, Homburg/Saar, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Volk
authors.affiliation: Department of Anesthesiology, Intensive Care Medicine and Pain Medicine Saarland University Medical Center, University of Saarland, Kirrbergerstrasse 1, 66421, Homburg/Saar, Germany.
authors.forename: Heinrich V
authors.initials: HV
authors.lastname: Groesdonk
authors.affiliation: Department of Anesthesiology, Intensive Care Medicine and Pain Medicine Saarland University Medical Center, University of Saarland, Kirrbergerstrasse 1, 66421, Homburg/Saar, Germany. andreas.meiser@uks.eu.
authors.forename: Andreas
authors.initials: A
authors.lastname: Meiser
mesh_terms: D000769:Anesthesia, Inhalation / Q000295:instrumentation*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D000077335:Desflurane / Q000008:administration & dosage*; D004867:Equipment Design; D006801:Humans; D007362:Intensive Care Units; D013990:Tidal Volume
chemical_list: D018685:Anesthetics, Inhalation; D000077335:Desflurane
keywords: AnaConDa™; Efficiency reflection; Intensive care unit (ICU); MIRUS™; Sedation