Unidirectional valves are a feature of which anesthesia system?

• A. Circular System
• B. Semi-Open System
• C. Open System
• D. Bag Breathing System

Answer: (A)

Unidirectional valves are used in the circle breathing system to direct gas flow in one direction, allowing gas to travel from the fresh gas inlet into the patient on inspiration while expiring gas is directed away from the fresh gas line toward the expiratory limb. This arrangement lets some of the exhaled gas be rebreathed after CO2 is removed by the absorber, conserving heat, moisture, and anesthesia gas while maintaining a closed or semi-closed circuit. Open systems, bag-breathing systems, and most semi-open Mapleson circuits do not rely on a pair of one-way valves in the main circuit, so they don’t provide the same controlled, unidirectional flow that the circle system does.