A. Type E
B. Type C
C. Type A
D. Type B
Ans:C. Type A.
Type A Mapleson breathing unit is shown in the image.
Mapleson breathing systems
- They are used for delivering oxygen and anesthetic agents and to eliminate carbon dioxide during anesthesia.
- They consist of different components: Fresh gas flow, reservoir bag, breathing tubes, expiratory valve, and patient connection.
- There are five basic types of Mapleson system:
A, B, C, D and E depending upon the different arrangements of these components.
Mapleson F was added later.
Mapleson A (Magill’s System)
- Fresh gas flow (FGF) inlet is near reservoir bag.
- APL (Adjustable Pressure Limiting) valve is near face mask.
Mapleson B and C
- FGF inlet and APL valve are close to face mask (FGF inlet being just distal to APL valve).
- Mapleson B has a corrugated tube, while the Mapleson C (Water’s circuit without an absorber) doesn’t have a corrugated tube.
- FGF inlet is close to patient’s face mask.
- APL valve is placed just before the reservoir bag, i.e. FGF inlet is proximal to APL valve.
Mapleson E (Ayre’s T piece)
- FGF inlet is close to face mask.
- No APL valve and reservoir bag.
Mapleson F (Jackson Ree’s Modification of Ayre’s T piece)
- Mapleson E with a reservoir bag at operator end.
- No APL valve
- Mapleson A for spontaneous respiration has the best efficiency of the six systems since fresh gas flow required to prevent rebreathing is equal to minute ventilation. For controlled ventilation, it is the worst system because very high fresh gas flows are required to prevent rebreathing.
- Mapleson D or Bain’s circuit is best for controlled ventilation.
- Mapleson B and C are rarely used today.
- Mapleson D, E, F require higher fresh gas flow to prevent rebreathing. They are next in order of preference list for spontaneous respiration. But they are better than Mapleson A for controlled ventilation.