Calculation of O2 consumption during low-flow anesthesia from tidal gas concentrations, flowmeter, and minute ventilation.
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.
Azami
Takafumi
T
Department of Anesthesiology and Resuscitology, Nagoya City University Medical School, Nagoya, Japan.
Preiss
David
D
Somogyi
Ron
R
Vesely
Alex
A
Prisman
Eitan
E
Iscoe
Steve
S
De Wolf
Andre M
AM
Fisher
Joseph A
JA
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
D002245:Carbon Dioxide