Anaesthetic Equipment Flashcards
what are the different types of gas supply? what are their cylinder colours?
oxygen = black with white shoulders
carbon dioxide = white or grey
air = white or grey
nitrous oxide = blue
how should you correctly store gas cylinders?
Undercover
Avoid temperature extremes
Dry
Clean
Size E (smallest) horizontally
Size F+ kept upright
what is a Bourdon pressure gauge? what considerations need to be made when using one?
tells us the volume of gas based of pressure in cylinder
- calibrated to individual gases
oxygen = compressed gas
- so cylinder pressure falls linearly as cylinder empties
nitrous oxide = liquid form
- so cylinder pressure only falls once all liquid has evaporated
- this causes a sudden fall on gauge
if cylinders are used on an anaesthetic machine a Bullnose needs to be added
- placed on top of the cylinder under pressure gauge
- prevents pressure surges to the patient
what safety features are there on anaesthetic equipment?
oxygen failing warning device
- bosuns whistle - high pitch noise
nitrous oxide cut-out
- when using NO and O2
- if O2 runs out NO supply will be cut off
- stops patient breathing 100% NO which could cause hypoxia
Pin index system
- ensures the correct cylinder is attached to the anaesthetic machine
- different pin positions for each gas type
Schrader probe
- diameter-specific probes to connect gas supply
- and colour-coded hoses and sockets
- ‘NIST’ noise when attaching correct hose to machine
what are the features of an anaesthetic machine?
back bar
- can hold up to 2 vaporisers
- contains an overpressure valve that opens if there is excess pressure - makes a hissing sound when activated
Flowmeter
Vaporiser
Oxygen Flush
- bypasses vaporiser
- never use with patient attached
- for flushing volatile agents out in an emergency
- or to check breathing system
Common gas outlet
- connects to breathing system
Emergency Air-Intake Valve
- opens if gas flow is disrupted
- delivers room air to patient
- a loud beep will sound when opening
What considerations need to be made when using a flowmeter?
bobbin = read from top
ball = read from middle
dot = spinning = flowing
hypoxic guard
- makes it impossible to deliver2 a high % of NO without a fixed % of 02 also being delivered
how to identify each gas
- oxygen = largest and on left
- air = black and middle
- nitrous oxide = right
how do vaporisers work?
gas is split into two streams
- one through the vaporising chamber to collect anaesthetic agent
- second through bypass channel
they are then reunited before leaving the vaporiser
concentration of the agent is controlled by the inlet valve which alters the splitting ratio of the gas
types of vaporisers?
each vaporiser is calibrated and designed to deliver a singe gas
- so if you fill with wrong agent (or mix) the concentrations will be wrong
two types:
keyed filling system
- agent-specific filling tube - attaches to the bottle then slots into vaporiser
- closed system - minimises environmental contamination
bottle adaptions
what are the different types of scavenging?
Passive
- absorber - contains activated charcoal which absorbs agents - must be weighed daily
- tubing from the breathing system to outside via outlet
Active
- fan/pump creates negative pressure
- pulls waste gases from breathing system
- safer
what can chronic exposure to anaesthetic gases cause?
spontaneous abortion
fertility issues
minor congenital abnormalities
leukaemia and lymphoma
liver and renal disease
immune system effects
what are the purposes of an anaesthetic circuit?
a connection between the patient and anaesthetic machine
to deliver oxygen-rich gas and agent to patient
to carry CO2 away from patient
deliver waste gases into scavenging system
to allow intermittent lung inflation
what are the two main types of anaesthetic circuits?
rebreathing
- soda-lime chamber to absorb CO2
- very economic on gases
- denitrogenation needed in the first 10mins of use
- concentration of anaesthetic vapour isn’t the same as concentration setting on vaporiser
- higher resistance to ventilation
non-rebreathing
- no CO2 absorption - cleared by high FGF
- normally have a pop-off valve
- low resistance to ventilation
- FGF rate needs to be calculated from minute ventilation
what do you need to consider when selecting the correct circuit type for a patient?
patient size
- lung capacity - not just weight
- think about ideal body weight
procedure
- rebreathing systems take time to equilibrate - initailly FGF will be high
- head and dental work had with some circuits
patient health
- reduced lung capacity?
- reduced need for IPPV?
- anaesthetic dosage given
- if infectious - need to sterilise or throw away
what are the key features of a t-piece?
non-rebreathing
simple to set up with no valves
minimal resistance to breathing
- useful for small animals (<10kg)
0.5l bag
can be modified or more efficient scavenging and IPPV
circuit factor = 2.5-3
what are the key features of a bain?
non-rebreathing
a compact co-axial system
- inspired gas down inner tube and expired gas up outer
- so inspiratoty gas is warmed by expired gas
minimal dead space
suitable for longterm IPPV
some resistance in the valves
- use for patients >10kg
circuit factor = 2.5-3
