High volatile anaesthetic conservation with a digital in-line vaporizer and a reflector

Acta Anaesthesiol Scand. 2018 Feb;62(2):177-185. doi: 10.1111/aas.13017. Epub 2017 Oct 25.


Background: A volatile anaesthetic (VA) reflector can reduce VA consumption (VAC) at the cost of fine control of its delivery and CO2 accumulation. A digital in-line vaporizer and a second CO2 absorber circumvent both of these limitations. We hypothesized that the combination of a VA reflector with an in-line vaporizer would yield substantial VA conservation, independent of fresh gas flow (FGF) in a circle circuit, and provide fine control of inspired VA concentrations.

Method: Prospective observational study on six Yorkshire pigs. A secondary anaesthetic circuit consisting of a Y-piece with 2 one-way valves, an in-line vaporizer and a CO2 absorber in the inspiratory limb was connected to the patient's side of the VA reflector. The other side was connected to the Y-piece of a circle anaesthetic circuit. In six pigs, an inspired concentration of sevoflurane of 2.5% was maintained by the in-line vaporizer. We measured VAC at FGF of 1, 4 and 10 l/min.

Results: With the secondary circuit, VAC was 55% less than with the circle system alone at FGF 1 l/min, and independent of FGF over the range of 1-10 l/min. Insertion of a CO2 absorber in the secondary circuit reduced Pet CO2 by 1.3-2.0 kpa (10-15 mmHg).

Conclusion: A secondary circuit with reflector and in-line vaporizer provides highly efficient anaesthetic delivery, independent of FGF. A second CO2 absorber was necessary to scavenge the CO2 reflected by the anaesthetic reflector. This secondary circuit may turn any open circuit ventilator into an anaesthetic delivery unit.

Publication types

  • Observational Study

MeSH terms

  • Anesthesia, Closed-Circuit / instrumentation*
  • Anesthesia, Inhalation
  • Anesthesiology / instrumentation*
  • Anesthetics, Inhalation / analysis*
  • Animals
  • Carbon Dioxide / isolation & purification
  • Nebulizers and Vaporizers*
  • Prospective Studies
  • Sevoflurane / analysis
  • Sus scrofa
  • Swine


  • Anesthetics, Inhalation
  • Carbon Dioxide
  • Sevoflurane