Breathing systems, CO2 absorbers and ventilators

anaesthetic machine breathing system soda lime ventilator Oct 29, 2026

Anaesthesia delivery relies on a chain of equipment working together seamlessly. The breathing system, the CO2 absorber and the ventilator each play a distinct role, and when one link falters, the whole chain is affected. Understanding how they connect helps us stay alert to the subtle signs that something needs attention.

The breathing system carries oxygen, air and anaesthetic vapour to the patient and removes exhaled gases. In circle systems, a CO2 absorber containing soda lime scrubs carbon dioxide from the circuit so gas can be safely rebreathed, conserving warmth, humidity and anaesthetic agent. The ventilator takes over mechanical breaths when manual ventilation isn't practical, relying on accurate pressure and volume delivery plus reliable alarms to flag problems early.

🔄 Circle systems recycle gas but depend on correctly functioning valves and absorbent
🧪 Exhausted CO2 absorbent shows a colour change and can cause rising inspired CO2
🫁 Ventilators need pressure, volume and alarm checks before every list
⚠️ Oxygen failure alarms and non-return valves guard against hypoxic mixtures
🔍 Structured, repeated checks keep every component in the chain trustworthy

For perianaesthesia nurses supporting the anaesthetist, this knowledge translates into real vigilance. Being familiar with the expected checks before a list and before each patient means we can help confirm equipment readiness and speak up if something seems off. Intraoperatively, we act as an extra set of eyes, noticing unusual circuit resistance, ventilator alarms or unexpected CO2 trends while the anaesthetist is focused elsewhere.

Small, consistent checks protect patients from big problems. Staying curious about how these systems interact makes us better partners in keeping anaesthesia safe.

Build Knowledge ✅

Improve Safety ✅

References:

Australian and New Zealand College of Anaesthetists (ANZCA). (2021). PS54(A) Position statement on the minimum safety requirements for anaesthesia machines and workstations for clinical practice 2021.
Australian and New Zealand College of Anaesthetists (ANZCA). (2026). PG31 Guideline on checking anaesthesia delivery systems 2026 (pilot).

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