Which component is bypassed when using the O2 flush valve?

• A. Vaporizers
• B. Reservoir Bag
• C. Flowmeters
• D. Unidirectional Valves

Answer: (A)

The O2 flush valve delivers a high-flow stream of oxygen directly into the breathing circuit, bypassing the vaporizer. That means the gas reaching the patient is not mixed with any anesthetic vapor, because it does not pass through the vaporizer where anesthetic agents are vaporized. The pharmacologic path of normal fresh gas goes through the flowmeters and then the vaporizer, so the flush bypasses that vaporizer stage. This is why the vaporizer is the component that’s bypassed. The reservoir bag, flowmeters, and one-way valves remain part of the circuit, but the flush route short-circuits the vaporizer.