Anaesthetic equipment Flashcards
What are the types of gas supplies?
cylinders
pipelines
oxygen concentrators
What are the main things to know about cylinders?
different sizes, treat with respect
+++ pressure
store under cover
protect from extreme temperatures
colour-coded for easy UD
pin index safety system of Esize cylinders (behind anaesthetic machine)
What is the pin index cylinder?
there is a washer (bodok seal) between cylinder and yoke
avoid delivering wrong gas to ptx
How does an oxygen cylinder look like?
Black cylinder white top
gauge pressure indicates volume left in cylinder
How does a medical air cylinder look like?
Grey cylinder, black/white quarters on top
gauge pressure indicates volume left in cylinder
How does a Nitrous oxide cylinder look like?
Blue cylinder
gauge pressure does NOT indicate volume left
weight cylinder
What are medical gas pipelines?
gas supplied from source outside building
safer
more economical
How do medical gas pipelines look like?
schrader valves and probes are non interchangeable
hoses connecting valves to anaesthetic machine are colour coded
What are oxygen concentrators?
takes in air and removes nitrogen from it, leaving an oxygen-enriched gas
needs a source of electricity
can give up to 10L/min, maximum of 95% O2 concentration
What does an anaesthetic machine consist of?
needed to deliver oxygen and other gases accurately
gas supply
pressure gauges
pressure regulators
flowmeters
emergency o2 flush
common outlet
vaporisers
What are the pressure gauges for?
forx oxygen and medical air, gauge indicates amount left in cylinder
for nitrous oxide we need to weigh the cylinder
What are pressure regulators for?
reducing valves
reduce cylinder pressure to a safe
keep pressure constant
positioned between cylinders and machine
What are flowmeters for?
measure flow rates of gases (L/min)
calibrates for a single gas
flow depends on ptx, breathing system, etc
How do we read flowmeters?
the flow rate is indicated by a bobbin or ball bearing floating in a transparent glass/plastic tube
read flow rate from:
TOP of bobbin
MIDDLE of ball bearing
What is the pressure relief valve for?
all machines will have one set so that if something blocks the outlet, the pressure does not rise so far that the machine comes apart
What is the emergency oxygen flush for?
it enables high flow of oxygen, bypassing the “back bar” therefore bypassing the vaporiser
ideally do not use while ptx is connected, will inflate them
quickly gets rid of anaesthetic gas from machine
What are vaporisers for?
vaporise liquid (volatile) anaesthetics to vapour
deliver known concentrations of anaesthetic
calibrated for one agent only
What are scavenging systems for?
reduces exposure of operating room personnel to waste anaesthetic agents vented from the breathing system
Wha are the recommended maximum accepted anaesthetic agent concentration sin the UK?
over 8h time weighted average
100ppm for nitrous oxide
50ppm for isofluorane
What are the 3 types of scavenging systems?
activated charcoal adsorders
passive systems
active systems
What do we need to know about activated charcoal absorber scavenging systems?
must be replaced every 12h or when at 1400g
dont absorb nitrous oxide
How do passive system scavenging systems work?
waste gases ducted out of window, pipe or extractor to fan outside
pollution of atmosphere
How do active system scavenging systems work?
connect to vacuum system
air brake must be utilised
What are the different purposes of the anaesthetic machine when connected to a ptx?
deliver oxygen
deliver anaesthetic gases
remove carbon dioxide from expired gas
provide means of ventilating animal
How do we classify anaesthetic breathing systems?
by how they eliminate CO2 from expired gas
- non-rebreathing
- rebreathing
How does non-rebreathing systems eliminate CO2 from expired gas?
carbon dioxide is removed by flow of fresh gas through system: no expired gas is re-used
How do rebreathing systems eliminate CO2 from expired gas?
carbon dioxide in expired gas is removed by absorption so that expired gas can be re-used
What is tidal volume?
volume of gas inspired or expired in one breath
What is minute volume?
the volume of air inspired or expired in one minute
How do we calculate total fresh gas flow?
estimate tidal volume, multiply RR = minute volume
MV x circuit factor = total fresh gas flow
What is the mapleson classification of anaesthetic breathing systems?
functional classification of non re-breathing systems
theoretical effeiciency in fresh gas use
fresh gas flow needed to prevent rebreathing expressed as a multiple of animal’s minute volume (circuit factor)
What is the circuit factor for mapleson A re-breathing systems?
1-1.5
What is the circuit factor for mapleson D and E re-breathing systems?
2.5-3
What non-rebreathing systems are suitable for animals under 10kg?
mini lack parallel
modified t piece
What are non-rebreathing systems suitable for animals over 10kg?
lack coaxial
lack parallel large
bain
What are the advantages of the rebreathing system circle?
by allowing rebreathing, much lower fresh gas flows are needed (economy)
reaction of absorbent with CO2 produces heat and moisture
What are the disadvantages of the rebreathing system circle?
exact composition of inspired gas unknown
changes in depth take longer
more expensive
What is a practical use of the circle?
initially use higher fresh gas flow for 10 first minutes
this is to flush air out of system and carry faster/more inhalant agent
When using a circle, when should we change the carbon dioxide absorbent?
when half of the colour has changed
colour can reverse if exhausted absorbent is left in the canister but it can’t be reused
How does soda lime carbon dioxide absorbers work?
when it reacts with anaesthetic agent there os production of carbon moxoxide and compound A
What are the steps to testing the breathing system?
never assume its not faulty
connect to anaesthetic machine
close APL valve (P = pressure = closed)
cover pts end with thumb
use oxygen flush to inflate reservoir bag
watch for leaks
open APL valve
What is important to check with co-axial systems?
to check the inner tube
turn on the oxygen flowmeter
use red device to briefly cover inner tube only
if its sealed the flowmeter will drop
