• Delphine Kern, Claire Larcher, Bertrand Basset, Xavier Alacoque, Rose Fesseau, Kamran Samii, Vincent Minville, and Olivier Fourcade.
• Department of Anesthesiology and Intensive Care, University Hospital of Toulouse, EA 4564 MATN, IFR 150, CHRU Toulouse Purpan, place du Dr Baylac, TSA 40031, 31059 Toulouse cedex 9, France. kern.d@chu-toulouse.fr
• Anesth. Analg.. 2012 Aug 1;115(2):310-4.

AbstractWe measured the time it takes to reach the desired inspired anesthetic concentration using the Primus (Drägerwerk, AG, Lübeck, Germany) and the Avance (GE Datex-Ohmeda, Munich, Germany) anesthesia machines with toddler and newborn ventilation settings. The time to reach 95% of inspired target sevoflurane concentration was measured during wash-in from 0 to 6 vol% sevoflurane and during wash-out from 6 to 0 vol% with fresh gas flows equal to 1 and 2 times the minute ventilation. The Avance was faster than the Primus (65 seconds [95% confidence interval (CI): 55 to 78] vs 310 seconds [95% CI: 261 to 359]) at 1.5 L/min fresh gas flow, tidal volume of 50 mL, and 30 breaths/min. Times were shorter by the same magnitude at higher fresh gas flows and higher minute ventilation rates. The effect of doubling fresh gas flow was variable and less than expected. The Primus is slower during newborn than toddler ventilation, whereas the Avance's response time was the same for newborn and toddler ventilation. Our data confirm that the time to reach the target-inspired anesthetic concentration depends on breathing circuit volume, fresh gas flow, and minute ventilation.

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