BJA Advance Access published online on April 30, 2004
British Journal of Anaesthesia, doi:10.1093/bja/aeh154
© 2004 by The Board of Management and Trustees of the British Journal of Anaesthesia
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1 The Department of Anesthesia and Critical Care Medicine, Hebrew University Hadassah School of Medicine, Jerusalem, Israel; Department of Critical Care Medicine, Room B7 08, Sunnybrook and Women’s College Health Sciences Centre, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5 Canada
Background. 1,1,1,2 Tetrafluoroethane is a hydrofluoroalkane (HFA) that is replacing chlorofluorocarbons (CFC) as a medical aerosol propellant in an attempt to reduce damage to the ozone layer. This study compared the effects of HFA- and CFC-based inhalers on four anaesthetic gas monitoring systems. Methods. The HFA- and CFC-based inhalers were activated in close proximity to the sample line of two Datex Ohmeda, an Agilent and a Siemens infrared anaesthetic agent monitoring systems. The effects were recorded on each system for five common anaesthetic agents. Results. The HFA inhaler caused either maximal false positive readings (with the exception of desflurane) or transient measurement failure on all systems. The Datex Ohmeda AS/3 system misidentified the HFA inhaler as carbon dioxide at low concentration (2 ± 0 mm Hg). The CFC-based inhaler caused a minor false-positive reading (0.4 ± 0%) for halothane only on the Datex Ohmeda AS/3 system only and was misidentified as carbon dioxide at 33.3 (SD 2.1) mm Hg and 22.4 (8.9) mm Hg by the Agilent and Siemens systems. Conclusions. The HFA inhaler adversely affected all equipment tested. The infrared spectra of HFA and the common anaesthetic gases have considerable overlap at the 8-12 µm range that is not shared by the CFCs. The differences in spectral overlap explain the different effects of the HFA and CFC propellants. Anaesthetic gas concentration data may be erroneous using the HFA-based inhalers.
Laboratory Investigation
Medical aerosol propellant interference with infrared anaesthetic gas monitors
2 The Department of Anesthesia and Critical Care Medicine, Hebrew University Hadassah School of Medicine, Jerusalem, Israel
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