Anaesthetic circuits and airway monitoring Flashcards
1
Q
what are some factors of choosing a circuit?
A
- resistance
-controlled versus spontaneous respiration - fresh gas flow requirements
- inclusion of nitrous oxide
- mechanical dead space
- circuit drag
- ease of maintenance and sterilisation
2
Q
what is a non rebreathing circuit?
A
- no co2 absorption or one way valves
- need a high fresh gas flow
- quick changes to volatile agent
- requires use of circuit factor calculation
3
Q
what are some examples of non-rebreathing circuits?
A
- lack
- mini lack
- bain
- ayres t-piece
- humphrey ADE system
4
Q
what is a lack and mini lack circuit?
A
- reservoir bag on inspiratory arm
- circuit factor of 1-1.5
- not suitable for long term IPPV
5
Q
what is a Ayres T-piece and Bain?
A
- reservoir bag on expiratory arm
- circuit factor 2.5-3
- can be used for long term IPPV
6
Q
what are some advantages of a non-rebreathing system?
A
- low resistance so suitable for small mammals and birds
- simple and inexpensive to buy
- no requirement for soda lime
- inspired anaesthetic concentration. can be easily and quickly adjusted
7
Q
what are some disadvantages of a non-rebreathing system?
A
- high oxygen requirements
- high anaesthetic agent requirements
- require knowledge of flow rate calculation
- lose heat and moisture in expired air (use HME)
8
Q
what is a rebreathing system?
A
- allow exhaled gases to be reused after the CO2 has been removed
- contain one way valves and co2 absorbent
- economical when used as a closed system as lower oxygen flow need
- reduce heat loss as warm air breathed in
- altering amount of agent takes time
9
Q
what are some advantages of rebreathing system?
A
- low gas flow requirements
- low volatile agent use
- expired moisture and heat is conserved
10
Q
what are some disadvantages of rebreathing system?
A
- high resistance
- expensive to purchase
- regular replacement of soda lime needed
- canister may be source of gas leak
11
Q
what does APL valve mean?
A
- adjustable pressure lifting valve
- prevents high pressures building up inside the circuit by opening when the pressure reaches a certain point allowing gas out but not air in
12
Q
what is the expiratory pause?
A
where no gas is being inhaled or exhaled by the patient but gas continues to flow into the circuit from the machine
13
Q
what is the ayres t-piece?
A
- can be used on patients less than 8kg
- circuit has low resistance and minimal dead space
- reservoir bag is on the expiratory limb
- APL valve on expiratory limb
- can be used for IPPV
- circuit factor 2.5-3
14
Q
what is a parallel lack?
A
- used on patients weighing over 10kg
- two gas carrying tubes running alongside or parallel to each other (one for fresh, one for waste)
- reservoir bag is on the inspiratory limb
- circuit factor 1-1.5
15
Q
what is a mini-lack?
A
- narrow tubing (less dead space)
- suitable for patients up to 10kg
- circuit factor 1-1.5
