Anaesthetic Circuits

Identify the following circuits

• Co-axial Bain

• 
• Paediatric Ayre's T-piece

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

• 
• Humphrey ADE

• 
• Magill

• 

Identify the following circuits

• Co-axial Lack

• 
• Parallel Lack

• 
• Mini-lack

• 
• Circle

• 

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

• Reduces required fresh gas flow after filling circuit

• Easier to predict how much agent the patient is receiving

• Recycled air is warmer and moister

• Delay in changes to agent percentage changes

• Required more gas

• Does not need soda lime

• Air is drier and cooler

• Saves on required anaesthetic agent

• Requires sodalime changes

• Instant effect from changes in agent percentage

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

• Reservoir Bag on expiratory limb

• Bain

• Not suitable for long term IPPV

• FGF rate 2.5-3

• Ayre's T-Piece

• Reservoir Bag on inspiratory limb

• Lack circuits

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

• Ayre's T-Piece (Paediatric)

• Low resistance tubing suitable for patients under 10kg

• Mini-lack

• Suitable for patients over 10kg

• Bain

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

• Lack

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

• Magill

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

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