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 (VO2) 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 VO2 and simulated VO2 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 VO2 and uptake of anesthetic is the precision of measurement of gas flow and gas concentration (especially O2 concentration in end-tidal gas, F [ABSTRACT FROM AUTHOR]