Isoflurane concentrations using uncompensated vaporisers within circle systems.
In a series of studies designed to investigate the need for a temperature-compensated vaporiser for use in a circle system, we first studied temperature changes within and isoflurane concentration delivered by a Komesaroff vaporiser during bench tests using different gas flows. Agent temperature and vapour concentration decreased as predicted by the Antoine equation. Using the vaporiser within a circle system during clinical anaesthesia, we then studied 20 patients breathing spontaneously and a further 10 patients receiving controlled ventilation, measuring the temperature of the agent within the vaporiser and the concentration of agent inspired by a the patient. In clincial use with the frest gas flows of 1-3.min-1, the inspired agent concentration did not decrease despite the decrease in temperature of the liquid isoflurane in the vaporiser.
Department of Anaesthetics, Northwick Park Hospital, Harrow, London, UK.
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S
Brosnan
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B
Royston
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D
White
D000764:Anesthesia, Closed-Circuit / Q000295:instrumentation*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D004334:Drug Administration Schedule; D006801:Humans; D007385:Intermittent Positive-Pressure Ventilation; D007530:Isoflurane / Q000008:administration & dosage*; D009330:Nebulizers and Vaporizers; D019637:Orthopedic Procedures; D013696:Temperature
D018685:Anesthetics, Inhalation; D007530:Isoflurane