Which component ensures one-way gas flow and prevents backflow in the breathing circuit?

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

Answer: (A)

One-way gas flow in the breathing circuit is achieved by unidirectional valves. These valves open to allow fresh gas from the anesthesia machine to move toward the patient during inspiration and close during expiration to prevent the exhaled gas from flowing back toward the machine or scavenging system. This one-way design prevents backflow, helps minimize rebreathing of CO2, and maintains stable gas concentrations delivered to the patient. The reservoir bag simply acts as a compliant volume for ventilation and doesn’t enforce direction. Flowmeters control how fast the fresh gas is delivered, and vaporizers add anesthetic vapor to that gas; neither controls the direction of flow.