Where can you set the desired concentration of anesthetic gas in a rebreathing system?

• A. At the top of the tank of gas
• B. At the pressure reducing valve
• C. At the flow meter
• D. At the dial on the vaporizer

Answer: (D)

Setting the desired concentration of anesthetic gas in a rebreathing system is done at the dial on the vaporizer. The vaporizer is the component that adds a precise amount of volatile anesthetic to the carrier gas, and the dial selects the percentage of inspired gas that is anesthetic vapor. The other controls don’t set concentration: the top of the gas cylinder or valve is the gas source, the pressure-reducing valve lowers cylinder pressure, and the flow meter controls how fast gas flows through the system. The concentration you want is determined by adjusting the vaporizer dial.