Converting a Closed System to a Semi-Closed System in Anesthesia Machines

Key Considerations for Conversion

To convert from a closed to a semi-closed system, increase the fresh gas flow (FGF) rate above the patient's metabolic consumption, typically setting FGF to 1-3 L/min, and ensure the adjustable pressure limiting (APL) valve is partially open to allow excess gas to escape through the scavenging system 1
Ensure the APL valve can be fully opened to allow excess gas to escape, and verify the valve is functioning properly by squeezing the reservoir bag during manual ventilation 1, 2
The APL valve must be connected to the scavenging system to prevent operating room pollution 1, 2

Perform a two-bag test to confirm proper circuit function, which includes attaching a test lung to the patient end, setting FGF to 5 L/min, and ventilating manually 1, 2
Verify the scavenging system is switched on and functioning, ensure tubing is properly attached to the exhaust port of the breathing system, and check for leaks in gas sampling lines 1, 2

Forgetting to open the APL valve can cause dangerous pressure buildup in a closed system when FGF is increased 1
Inadequate scavenging can lead to operating room pollution, and it is crucial to ensure proper scavenging when increasing FGF 1, 2
Ignoring CO₂ absorbent is a common pitfall, as semi-closed systems still require functional CO₂ absorption; check absorbent color and supply 2, 3