Anaesthetic Breathing Systems Flashcards
What is a ‘Non-rebreathing system’? Can you give some examples?
Enough fresh gas flow is put in to prevent rebreathing, no expired gas is re-used. E.g. Lack, Magill, Bain, Ayre’s T-piece.
What is a ‘Rebreathing system’? Can you give some examples?
CO2 expired and removed usually by chemical means (usually soda-lime). If it has a cannister with granules its a REBEATHING. e.g. Circle, To and Fro.
What are the advantages of a non-rebreathing system?
Simple and cheap, Inspired gas composition known, low resistance to breathing, rapid anaesthesia depth change.
What are the disadvantages of a non-rebreathing systems?
High gas flow requried (if not enough, may rebreathe expired air), high volatile agent consumption, expired heat/moisture lost.
What are the advantages of a rebreathing system?
Lower fresh gas flows, don’t usually have to calculate just enough for metabolic needs, low volatile agent consumption, warm and humidified gas.
What are the disadvantages of a rebreathing system?
Exact composition of rebreathed gas unknown, expensive, slow depth change.
How do you calculate total gas flow needed?
Minute volume = Tidal volume (weight in kg x 10-15ml) x RR
Total fresh gas flow = MV x System Factor
What type of breathing system is a Magill? Where is the reservoir bag? What is the circuit factor of a Magill breathing system?
Non-rebreathing system, with reservoir on inspiratory limb. Circuit factor of 1-1.5 x
Is the Magill breathing system suitable for IPPV? What weight animals would you use a Magill system on?
Not a good choice for IPPV as it needs much higher flow rates. Suitable for animals >10kg.
What type of breathing system is a Lack? Where is the reservoir bag? What is the circuit factor of a Lack breathing system? What two types of lack can you get?
Non-rebreathing system, with reservoir on inspiratory limb. Circuit factor of 1-1.5 x. Can get coaxial (not used) or parallel lack.
Is the Lack breathing system suitable for IPPV? What weight animals would you use a Lack system on?
Not a good choice for IPPV as it needs much higher flow rates. Standard lack Suitable for animals >10kg, mini lack suitable for use on animals <10kg.
What type of breathing system is a Ayre’s T piece? Where is the reservoir bag? What is the circuit factor of a Ayre’s T piece breathing system? What variants can you get?
Non-rebreathing system, with reservoir on expiratory limb. Circuit factor of 2.5-3 x. Can get standard T piece, Jackson Ree’s T piece etc.
Is the Ayre’s T piece breathing system suitable for IPPV? What weight animals would you use a Ayre’s T piece breathing system on?
Good choice for IPPV as high flow rates. Low resistance so suitable for animals <10kg.
What type of breathing system is a Bain? Where is the reservoir bag? What is the circuit factor of a Bain breathing system? Is the bain parallel or coaxial?
Non-rebreathing system, with reservoir on expiratory limb. Circuit factor of 2.5-3 x. It is coaxial with the inspiratory tube on the inside.
Is the Bain breathing system suitable for IPPV? What weight animals would you use a Bain breathing system on?
Good choice for IPPV as high flow rates. Used on dogs over 10kg, however uneconomical in larger animals.
What is IPPV?
Intermittent positive pressure ventilation
What type of breathing system is a circle system? What weight animals would you use a circle system breathing system on?
Rebreathing system. High resistance to breathing so generally only used in animals >10kg.
In a circle system, what dose of fresh gas flow is given a) initially (first 10-15 mins), b) once stable plane of anaesthesia.
A) High FGF rate (100ml/kg/min)
B) Reduced to 50ml/kg/min
