A simple T-junction with no reservoir bag and no valves. Best For: Pediatric patients (under 25–30kg).
| Circuit | Key Feature | Best Use | Efficiency (FGF to prevent rebreathing) | | :--- | :--- | :--- | :--- | | | FGF near patient; APL valve near bag | Spontaneous Ventilation | Very low (~70-100 mL/kg/min) | | Mapleson B | FGF between patient and APL (rare today) | Historical | Poor | | Mapleson C | FGF at same T-piece as APL | Short procedures (transport) | Moderate | | Mapleson D (Bain) | Coaxial; FGF near patient; APL at machine end | Controlled Ventilation | Low (~100-150 mL/kg/min) | | Mapleson E (Ayre's T-piece) | No valve; open tail | Pediatrics (SV) | High flow (2-3x MV) | | Mapleson F (Jackson-Rees) | Ayre's T-piece with open-ended bag | Pediatrics (SV or CV) | Moderate-High |
Understanding Mapleson circuits is vital for any healthcare professional involved in airway management. While the is the king of spontaneous breathing, the Mapleson D (Bain) and Mapleson F remain the workhorses of controlled ventilation and pediatric care, respectively.
If FGF is too low, the patient rebreathes their own CO₂, leading to hypercapnia, tachycardia, and hypertension. If FGF is too high, we waste expensive volatile agents and pollute the operating room. The key to mastering Mapleson circuits is understanding which system is efficient for versus controlled ventilation (CV) .
