2016A02 Draw and label a circle breathing system. Explain its advantages and disadvantages.

· Define

· Diagramme

· Pros

· Cons

Circle system is a semi-closed, re-breathing anaesthetic circuit.

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Main features

· Volatile anaesthetic: accurate, minimal waste

· O₂: accurate, can deliver 100%

· CO₂: efficient removal by

o Scavenger (earlier in expiratory limb – to spare CO₂ absorber))

o CO₂ absorber (later in expiratory limb)

Secondary features

· Minimal dead space: only tubing distal to Y piece and HME

· Low resistance

· Humidification and warming by CO₂ absorber

Logistics

· Sodalime remote from airway hence minimal dust inhalation

· ↓Waste

· ↓O₂ pollution

Main features

· Change in vapour dial slow to equilibrate with circuit and patient

· FiO₂ can fall below 0.21 if low fresh gas flow rate and low fresh gas pO2 (since semi-closed)

· Sodalime degradation products: CO, Compound A

Secondary features

· Higher resistance than Mapleson E and F due to valves and longer tubing

· Possibility of injury if dysfunctional valves, scavenging system

Logistics

· Expensive

· Complicated

· Bulky

· Atmospheric pollution from scavenging