Anaesthetic Circuits

Identify the following circuits

• Paediatric Ayre's T-piece

• 
• Jackson-Rees Modified Ayre's T-Piece

• 
• Co-axial Bain

• 
• Humphrey ADE

• 
• Magill

• 

Identify the following circuits

• Mini-lack

• 
• Co-axial Lack

• 
• Circle

• 
• Parallel Lack

• 

The difference between a rebreathing circuit from a non-rebreathing circuit is:

• Rebreathing circuits will have a soda lime cannister

• Non-rebreathing circuits will have a soda lime cannister

• Rebreathing circuits have a reservoir bag on the inspiratory limb

• Non-rebreathing circuits have a reservoir bag in the inspiratory limb

Differentiate rebreathing and non-rebreathing advantages and disadvantages

Groups:

(a) Rebreathing

,

(b) Non-rebreathing

• Air is drier and cooler

• Easier to predict how much agent the patient is receiving

• Reduces required fresh gas flow after filling circuit

• Requires sodalime changes

• Required more gas

• Recycled air is warmer and moister

• Instant effect from changes in agent percentage

• Saves on required anaesthetic agent

• Delay in changes to agent percentage changes

• Does not need soda lime

Identify features and circuits within Mapleson Categories

Groups:

(a) Mapleson A

,

(b) Mapleson D

• Suitable for long term IPPV

• FGF rate 0.8-1 or 1-1.5

• Lack circuits

• Reservoir Bag on expiratory limb

• Bain

• Not suitable for long term IPPV

• Ayre's T-Piece

• 
• 
• Reservoir Bag on inspiratory limb

• FGF rate 2.5-3

The original Ayre's T-piece has no reservoir bag, so is categorised as Mapleson E. The paediatric Ayre's T-piece has a closed bag and APL valve so is Mapleson D. The Jackson-Rees modified Ayre's T-piece:

• Has an open ended reservoir bag so is classed as Mapleson F

• Is not real, it can't hurt you

• Has its reservoir bag on the inspiratory limb so is Mapleson A

• Has no corrugated tubing so is Mapleson C

Match use for each non-rebreathing circuit

• Magill

• Low resistance, low dead-space circuit great for patients under 8kg

• Ayre's T-Piece (Paediatric)

• High resistance, suitable for patients over 10kg but very high FGF rates make it uneconomical above 15kg

• Mini-lack

• Suitable for patients over 10kg but rarely used due to impracticality of surgery near head and neck

• Lack

• Suitable for patients over 10kg

• Bain

• Low resistance tubing suitable for patients under 10kg

How can the issue of rebreathing expired air be combated in IPPV with Lack (Mapleson A) circuits?

• Decreasing fresh gas flow rates

• Using lower fresh gas flow rates

• Increasing fresh gas flow rates

• Maintaining the same fresh gas flow rates

What happens to gases in Lack (Mapleson A) circuits?

• They are drawn from the inspiratory limb and pushed out through the expiratory limb and APL valve

• They are stored in a reservoir for later use

• They are released into the atmosphere

• They are recycled back into the anesthesia machine

What potential issue can arise when giving IPPV in these circuits?

• Increased oxygenation

• Decreased heart rate

• Disturbed pattern causing the patient to rebreathe expired air

• Improved lung compliance