A-Z Anaesthesia: Mapleson Classifications

Question 1

MAPLESON A: Describe advantage FGF required?

Answer 1

Most efficient for spontaneous ventilation:

• because exhaled dead-space gas is reused at the next inspiration,
• exhaled alveolar gas passes out through the valve.
• Thus fresh gas flow (FGF) theoretically may equal alveolar minute volume (70 ml/kg/min).

Question 2

Disadvantage of MAPLESON A

Answer 2

Inefficient for IPPV:

• some fresh gas is lost through the valve when the bag is squeezed,
• exhaled alveolar gas may be retained in the system and rebreathed.
• High gas flows are therefore needed (2–3 times minute volume).

Question 3

MAPLESON B and C uses FGF required?

Answer 3

Mapleson B and C:

rarely used, other than for resuscitation.

Inefficient; thus 2–3 times minute volume is required.

Question 4

MAPLESON D: Advantage

Answer 4

Efficient for IPPV:

• exhaled dead-space gas passes into the bag and is reused but when alveolar gas reaches the bag, the bag is full of fresh gas and dead-space gas;
• alveolar gas is thus voided through the valve.
• Theoretically, 70 ml/kg/min will maintain normocapnia.

Question 5

MAPLESON D: Disadvantage How to prevent rebreathing? Suggested FGF? Problems with high FGF?

Answer 5

Inefficient for spontaneous ventilation:

• because exhaled gas passes into the reservoir bag with fresh gas, and may be rebreathed unless FGF is high.
• Suggested values for FGF range from 150 to 300 ml/kg/min (i.e., 2–4 times minute ventilation)
• resistance to breathing may be a problem at high FGF.

Question 6

MAPLESON E: Uses Advantages? How to prevent rebreathing? Suggested FGF? How can IPPV be used?

Answer 6

Also known as AYRE’S T PEICE:

• used for children, because of its low resistance to breathing.
• To prevent breathing of atmospheric air, the reservoir limb should exceed tidal volume.
• A FGF of 2–4 times minute volume is required to prevent rebreathing.
• May be used for IPPV by intermittent occlusion of the reservoir limb outlet.

Question 7

MAPLESON F Advantage? Suggest FGF? ?ml/kg/min

Answer 7

Mapleson F (Jackson–Rees modification):

adapted from Ayre’s T-piece. The bag allows easier control of ventilation, and its movement demonstrates breathing during spontaneous ventilation.

Suggested FGF: 2–4 times minute volume for spontaneous ventilation.

For IPPV, 200 ml/kg/min has been suggested, although more complicated formulae exist.

Question 8

Which system uses a varied reservoir bag?

Answer 8

Mapleson F, a modification of E, uses an open ended reservoir bag that allows a controlled leak and PEEP. This is the Jackson Rees Modification.

Question 9

Capacity of Reservoir bag?

Answer 9

2L

Question 10

Which Mapleson Circuit has:

1. FGF close to patient?
2. Valve closest to patient?
3. No reservoir bag?
4. No valve?

Answer 10