Anaes · Breathing systems & circuits

Breathing systems & circuits

Also known as Mapleson classification · Bain circuit · Circle system · Ayres T-piece · Rebreathing

The breathing system is the interface between the anaesthetic machine and the patient — it delivers the fresh gas and the volatile agent, removes the carbon dioxide, and provides the means for spontaneous and controlled ventilation. The framework rests on four exam-critical ideas: the Mapleson classification (A to F) organises the non-rebreathing and the partial-rebreathing systems by the arrangement of the components; the circle system (the modern standard adult system) uses the unidirectional valves and the CO2 absorber to allow the rebreathing of the exhaled gas at the low fresh gas flows; the efficiency of each Mapleson system is determined by the fresh gas flow requirement relative to the minute ventilation (the Mapleson A is the most efficient for the spontaneous ventilation, the Mapleson D for the controlled ventilation); and the CO2 absorption chemistry (the soda lime and the modern absorbents) underpins the safe rebreathing. Built on the CO2 absorption review (Feldman 2021), the closed-circuit review (Parthasarathy 2013), the Mapleson systems review (Kaul 2013), the machine checklist and hazards review (Goneppanavar 2013), and the AAGBI checking guidelines (2012).