title: Calculation of O2 consumption during low-flow anesthesia from tidal gas concentrations, flowmeter, and minute ventilation.
abstract: We present the principles of a new method to calculate O2 consumption (V*O2) during low-flow anesthesia with a circle circuit when the source gas flows, end-tidal O2 concentrations and patient inspired minute ventilation are known. This method was tested in a model with simulated O2 uptake and CO2 production. The difference between calculated V*O2 and simulated V*O2 was 0.01 +/- 0.02 L/min. A similar approach can be used to calculate uptake of inhaled anesthetics. At present, with this method, the limiting factor in precision of measurement of V*O2 and uptake of anesthetic is the precision of measurement of gas flow and gas concentration (especially O2 concentration in end-tidal gas, FETO2) available in clinical anesthetic units.
authors.affiliation: Department of Anesthesiology and Resuscitology, Nagoya City University Medical School, Nagoya, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Azami
authors.forename: David
authors.initials: D
authors.lastname: Preiss
authors.forename: Ron
authors.initials: R
authors.lastname: Somogyi
authors.forename: Alex
authors.initials: A
authors.lastname: Vesely
authors.forename: Eitan
authors.initials: E
authors.lastname: Prisman
authors.forename: Steve
authors.initials: S
authors.lastname: Iscoe
authors.forename: Andre M
authors.initials: AM
authors.lastname: De Wolf
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Fisher
mesh_terms: D000769:Anesthesia, Inhalation / Q000379:methods*; D002245:Carbon Dioxide / Q000032:analysis; D006801:Humans; D008962:Models, Theoretical; D008991:Monitoring, Physiologic; D010101:Oxygen Consumption; D012119:Respiration; D012121:Respiration, Artificial; D012680:Sensitivity and Specificity
chemical_list: D002245:Carbon Dioxide