title: Charcoal as an airway isoflurane reflection filter.
abstract: The isoflurane-saving and CO2-retaining effects of a charcoal filter were compared with a Siemens standard heat and moisture (HME) exchanger and an emptied specimen (dummy). Isoflurane was delivered during the inspiratory phase and consumption investigated at 10, 15 and 25 cycles min-1. The investigation was performed by ventilation with humidified air with a constant end-tidal CO2 and temperature. For a comparison, isoflurane was delivered in a conventional manner via the ventilator. The arrangement with a charcoal filter reduced the isoflurane consumption by a factor of 2.0-2.6, depending on ventilatory rate. Most of the saving was a result of the method of isoflurane delivery (factor 1.4-2.0), while adding the reflector gave a further reduction (factor 1.3-1.5). One circumstance that reduced the net efficiency of the charcoal filter was that it also reflected CO2; consequently, total minute ventilation had to be increased to maintain constant end-tidal CO2.
authors.affiliation: Department of Anaesthesia, University Hospital of Lund, Sweden.
authors.forename: S L
authors.initials: SL
authors.lastname: Dahm
authors.forename: P
authors.initials: P
authors.lastname: Steptoe
authors.forename: H H
authors.initials: HH
authors.lastname: Luttropp
authors.forename: P
authors.initials: P
authors.lastname: Reinstrup
mesh_terms: D000327:Adsorption; D000776:Anesthesiology / Q000295:instrumentation*; D018685:Anesthetics, Inhalation / Q000737:chemistry*; D002245:Carbon Dioxide / Q000032:analysis; D002606:Charcoal; D005374:Filtration / Q000379:methods; D007530:Isoflurane / Q000737:chemistry*
chemical_list: D018685:Anesthetics, Inhalation; D002245:Carbon Dioxide; D002606:Charcoal; D007530:Isoflurane