Abstract
In general anesthesia (GA) using the semi-closed ventilation, carbon dioxide (CO2) needs to be removed from the expired gas by absorber. The primary factor that determines the amount of CO2 recirculation is the fresh gas (FG) flow rate. The purpose of this study is to design a semi-closed ventilation model and quantitatively analyze the effect of the FG flow rate on the CO2 absorption during GA. Methods: The ventilation process is modeled as follows. During the inspiration, FG is blended with recycled gas from the bellows and sent to patients. The gas from the bellows passes the absorber, and CO2 is eliminated before mixing with the FG. During the expiration, the expired gas and FG is stored in the bellows. Once the bellows is filled, the spillover gas is scavenged into the draining system. The simulation program was developed, and the amount of CO2 absorption was calculated as per varied ventilation settings. Results: The simulation demonstrated that the CO2 load on the absorber increases in a non-linear manner as the FG flow rate decreases. This simulation model can be used to measure the cost-effectiveness and environmental impacts of different ventilation settings during GA.
