A FORMULA TO CALCULATE OXYGEN-UPTAKE DURING LOW-FLOW ANESTHESIA BASEDON FIO2 MEASUREMENT

Monitoring of oxygen uptake during general anesthesia would have sever al benefits, but unfortunately this is usually not available in the cl inical routine situation. The herein proposed formula to calculate oxy gen uptake ((V)over dot O-2) necessitates only the accurate measuremen t of FIO2 as well as fresh gas flow and composition. Additionally, thi s method is not affected by the presence of anesthetic gases. The calc ulation uses the difference in oxygen content between the delivered fr esh gas and the resulting FIO2 in the anesthesia circle system. This g ap originates from oxygen uptake (that is mainly caused by metabolic o xygen consumption) and is more pronounced if low fresh gas flows are a dministered. In order to obtain representative results, calculation of (V)over dot O-2 should be performed only after achievement of respira tory steady state conditions. Due to its simplicity and wide availabil ity, it has the potential to become a valuable extension in anesthesia monitoring during the performance of routine generai anesthesia.