anaesthesia - circuits Flashcards
what colour are oxygen cylinders?
black with white top or all white
what colour are N2O cylinders?
blue
what colour are air cylinders?
grey with black and white top
what is the difference between oxygen and nitrous gauges?
-oxygen the gauge indicated the volume left -nitrous the gauge will read full if anything in it so weight it (due to vapour)
what is the pin-index system?
so the wrong cylinder cant be connected to wrong yoke on the machine
what is the bodek seal?
between cylinder and machine for gas tight seal
what are schrader valaves?
at end of pipe supply so cant connect wrong cylinder to pipe -colour coded
what does the pressure regulator (reducing valve) do?
reduces cylinder pressure so safer and constant -between the cylinder and flowmeter
what do flowmeters and needle valves do?
mesure flow rate of a single gas, controlled mannually
what is a vaporizer?
a chamber containing the volatile anaesthetic agent that a portion of the fresh gas passes through -keep upright -fill with key-index system
what is the pressure release valve?
releases gases into room if builds up in system so doesnt go into animal
what is scavenging?
all waste gases
what is minute volume?
TV x RR
what is normal Tidal volume?
10-15 ml/kg
10 for larger animals
what is an approximation of minute volume?
200 ml/kg/min
how is fresh gas flow calculated?
minute vol x circuit factor
= weight x 10-15 ml x rr x system factor
= or 200ml/kg x system factor
what happens is FGF is too low?
will rebreathe
advantages of non-rebreathing systems
cheap co2 absorber not needed what is inspired controlled by flowmeter and vaporiser low resistance to breathing rapid change in depth possible
disadvantages of non-rebreathing systems
high FGF needed high consumption of volatile agent expired heat and moisture lost
advantages of rebreathing systems
lower FGF more economical low volatile agent consumption rebreathed gas is already warm and humidified
disadvantages of rebreathing systems
exact inspired composition unknown expensive slow to change depth
What systems can you IPPV on?
Ayers Bain Circle
what is a magill system?
non-rebreathing -animals over 10 kg -circuit factor 1-1.5 -valve close to drapes so not used much
which system can be used on animals under 10 kg?
mini lack ayre’s t piece humphrey ADE
what is a lack system?
non-rebreathing
- standard over 10 kg, mini 2- 10kg
- circuit factor 1-1.5
what is an ayre’s T piece system?
non-rebreathing -can use under 10 kg -circuit factor 2.5-3
what is a bain system?
non-rebreathing -over 10 kg but not too big(over 20) -circuit factor 2.5-3
what is a humphrey ADE?
non-rebreathing -circuit factor alters with weight -valve up (A) - for spontaneous respiration -valve down (D/E) - for IPPV
what is a circle system?
rebreathing -need a soda lime canister -only over 10 kg -when first connect use high FGF until animal stable
what is a to- and -fro system?
rebreathing -horses in the field -cannister near ET tube and heavy so can pull out
what is the komesaroff and stephen’s machines?
rebreathing -circle with a low resistance vaporiser in circuit
What system is this?
Magill
non-rebreathing
What system is this?
Lack (parallel)
coaxial would have one tube inside the other
What system is this?
Ayre’s T piece
What system is this?
Bain
What system is this?
Humphrey ADE
What system is this?
Circle
What is the mapleson classification?
from A-F related to efficncy and how much FGF is needed
Steps to checking an anaesthetic machine
1) switch on full reserve cylinder
2) pressure should be 150kPa
3) check o2 flush
4) check flowmeter - check bobbin rises and returns to zero and is spinning
5) turn off full reserve
6) turn on flowmeter to hear o2 alarm as o2 empties from machine
7) turn on in use cylinder and state pressure
8) check nitrous if fitted
9) check vaporiser - firmly attached, check fluid level, check dial on top moves freely
10) check for leaks in circuit - o2 on, attach circuit and close APL valve and occlude patient end and turn on flowmeter - resevoir bag should fill (listen for leaking) and the bag should stay inflated when squeezed. Open APL valve and squezee bag and gas should go out scavenging
11) if coaxial check inner tube by occluding it
What system would you use for a small animal that may need ippv?
ayre’s t piece
what system do ou use for a dog over 20 kg?
magill or lack
what system would you use for a dog over 20 kg and need to IPPV?
circle
what does APL stand for?
adjustable pressure limiting
which non-rebreathing circuits are most economical?
magill and lack (ml)
low circuit factor
cant IPPV
*magill has APL valve at mouth end
