Can an Anesthesia Machine's Closed System Be Used Without a CO2 Absorber?
No, a closed or low-flow circle system cannot be safely operated without a functional CO2 absorber, as this will result in dangerous CO2 rebreathing and life-threatening hypercapnia. 1
Understanding Circle System Requirements
The circle breathing system fundamentally depends on CO2 absorption to allow rebreathing of exhaled gases. When you reduce fresh gas flow (which defines a "closed" or "low-flow" system), the CO2 absorber becomes absolutely essential:
- Circle systems require adequate CO2 absorbent supply - Guidelines explicitly mandate inspecting the CO2 absorber contents, connections, and checking the color of the absorbent before use 1
- CO2 absorbers enable low-flow anesthesia by removing exhaled CO2, allowing safe rebreathing of anesthetic agents and oxygen while minimizing waste 2
- Malfunction of the CO2 absorption system leads to hypercapnia, which can cause tachyarrhythmias, myocardial ischemia, and increased sympathetic activity, particularly dangerous in patients with coronary artery disease 3
Converting to an Open System Alternative
If you need to operate without a CO2 absorber, you must fundamentally change the system configuration:
- Remove the CO2 absorber entirely and dramatically increase fresh gas flow to at least 6 L/min or higher to prevent CO2 rebreathing 4
- This converts the circle system to a semi-open configuration, where high fresh gas flow washes out exhaled CO2 before significant rebreathing occurs 4
- Use alternative breathing systems such as Bain-type circuits or other non-rebreathing systems that don't rely on CO2 absorption 1, 5, 6
Critical Safety Considerations
Common pitfall: Simply removing the CO2 absorber while maintaining low fresh gas flows will cause rapid CO2 accumulation and patient harm 3
- Monitor end-tidal CO2 continuously - Any rise in inspired CO2 above 0.3 kPa (approximately 2 mmHg) indicates inadequate CO2 elimination 4
- Economic and environmental trade-offs exist - Operating at 6 L/min fresh gas flow without a CO2 absorber reduces absorbent costs by up to 93% but more than doubles the environmental impact compared to using an absorber with lower flows 4
- During COVID-19 or infectious cases, the Chinese Society of Anesthesiology recommends replacing CO2 absorbers between cases due to the large surface area that could harbor pathogens 1
Practical Algorithm
- If CO2 absorber is exhausted or unavailable: Increase fresh gas flow to ≥6 L/min immediately
- If continuing without absorber: Remove the canister entirely and maintain high flows (6-10 L/min)
- Monitor inspired CO2: Must remain <0.3 kPa; if it rises, increase fresh gas flow further
- Consider switching to a non-rebreathing circuit (Bain, Mapleson) for more predictable performance without CO2 absorption 5, 6
Bottom line: A "closed system" by definition requires CO2 absorption. Without it, you no longer have a closed system—you have a high-flow semi-open system with significantly increased gas consumption and waste. 2, 4