Anaesthetic Machine and Breathing Systems

Question 1

colours - gas cylinders

Answer 1

oxygen - white/black top
nitrous - blue

Question 2

colours - wall taps

Answer 2

oxygen - green
nitrous - blue
medical air - yellow

Question 3

alternative oxygen sources

Answer 3

crytotanks - take up less space for more stored gas
oxygen generator - filters room air to remove nitrogen

Question 4

check valve

Answer 4

makes sure gas only moves one direction

Question 5

pressure gauge

Answer 5

measures pressure

Question 6

regulator

Answer 6

keeps gas pressure constant

Question 7

flowmeter

Answer 7

measures oxygen flow

Question 8

vaporiser

Answer 8

makes anaesthetic into gas form

Question 9

oxygen flush

Answer 9

lets out oxygen bypassing vaporiser

Question 10

intermittent positive pressure ventilation (IPPV)

Answer 10

intermittent manual - sighing - close valve, do a breath, open again
continuous manual
mechanical - ventilator

Question 11

checks

Answer 11

visual checks
leak test - thumb over pop off valve and check bag inflates
brain - occulde end with a syringe and check flow drops
soda lime - colour change

Question 12

gas storage

Answer 12

combustion - keep away from flames/heat/sparks
puncture - can rocket cyclinders around
store upright and secure to wall
keep tops dust free
recap when empty
open windows and wear gloves/mask if spilled

Question 13

safety features on machine

Answer 13

oxygen failure alarm
nitrous cut off - if oxygen pressure falls
hypoxic mixture alarm - if oxygen percentage in mixed gas too low
ventilator alarm - low or high airway pressures
interlocks between vaporisers - only one volatile agent introduced at once
pin index safety system on cylinders - only connect right pipe
non interchangeable connectors - can’t plug into wrong wall socket

Question 14

scavenging

Answer 14

vent waste gases - harm to people and patients, ozone gases
reducing pollution

charcoal cannister - cardiff aldasrober - charcoal absorbs halogenated anesthetics, weight increases when exhausted
passive - tube out of window
active - pumped outside

Question 15

reducing pollution

Answer 15

adequate ventilation - 20 air changes per hour
circle systems
TIVA
regional anaesthesia
fill vaporiser at end of day
scavending
cuffed tubes
regular equipment inspection
only turn on gas if animal connected

Question 16

functions of breathing circuits

Answer 16

supply fresh gas and anaesthetic
remove CO2
allow scavenging
enable PPV
easy to clean and use
cheap to buy and use

Question 17

factors affecting circuit selection

Answer 17

resistance - increases with length, decreases with width
re breathing
fresh gas flow requirement
dead space
circuit drag
cleaning and maintenance
ease of scavenging

Question 18

rebreathing systems

Answer 18

large animals

conserves heat and moisure
increased resistance
inspired gas scrubbed by soda lime
unidirectional valves

gas flow - metabolic oxygen demand - 10ml/kg/min - but needs higher flow for first 10 mins and after disconnections to avoid alveolar hypoxia

Question 19

non-rebreathing

Answer 19

smaller animals

high gas flow requirement
minute volume x circuit factor
minute volume = rr x tidal volume

cheap to buy, expensive to run
low resistance

Question 20

macgill

Answer 20

reservoir bag at outlet
circuit factor = 1

Question 21

lack

Answer 21

coaxial macgill - tube inside tube
damage to inner tube leads to rebreathing
circuit factor = 1

Question 22

mini lack

Answer 22

1-10kg
2 tubes
low resistance
can do IPPV
circuit factor = 1

Question 23

T piece

Answer 23

under 8kg
can do IPPV
circuit factor = 2-3

Question 24

bain

Answer 24

coaxial t piece
damage to inside tube - rebreathing
circuit factor = 2-3

Question 25

humphrey ADE

Answer 25

3 modes - lack, t piece, circle
versatile and compact
scavenges
can do IPPV

heavy
expensive
south african colour coded
not many veterinary controlled trials