Anaesthetic Machine & Circuits Flashcards
What does the anaesthetic machine provide?
-delivers gaseous inhalation anaesthesia and a supply of carrier gas
-provide steady flow of anaesthetic gases to patient and allows adjustments to rate of flow
What is anaesthetic machine made up of?
-carrier gas source
-pressure gauge
-pressure reducing valve
-flow meters
-vaporiser
-comm gas outlet
-emergency oxygen flush
What does the pin index for gas cylinders ensure?
-that the correct cylinder is connected to the correct port
What are piped gases?
-carrier gases stored outside of building
-pipeline carrier gases from exterior of building to connect to anaesthetic machine
What are oxygen concentrators?
-generates 02 from room air via pressure sieve
-relies on electrical supply
What does the pressure gauge show?
-the pressure of gas in the cylinder
-indicates the remaining content
What is the pressure reducing valve?
-safety mechanism between cylinder and other parts
-reduces pressure of gas coming from cylinder making it easier to control
-avoids damage to patients respiratory tract
What does flow meter show?
-shows level of gas flow supplied to patient
-bobbin read from top
-ball read from middle
What does the vaporiser contain?
-the liquid volatile agent to be mixed with carrier gas
What is an in circuit vaporiser?
-animals own respiratory efforts control amount of volatile agent received
What is an out of circuit vaporiser?
-FGF from machine vaporises the inhalational agent
What is the common gas outlet?
-where the gaseous anaesthetic connects to the patient supply
What safety features are on anaesthetic machine?
-pin index
ensure connection of correct cylinder to correct outlet
-oxygen alarm
(whistle sound when oxygen levels fall)
-emergency 02 flush
(delivers 100% oxygen to patient bypassing vaporiser and flow meter)
What does a scavenger allow?
-minimised exposure to waste gases
What is passive scavenging?
-inefficient as relies on patients respiratory efforts control efforts and affected by resistance in tubing
What is active-passive scavenging?
-tubing connected to a forced ventilation system
What is activated charcoal?
-absorbs waste gases
How is risk of anaesthetic machines minimised?
-adequate ventilation of working environment
-effective scavenging system in place
-sensible working practice
-low flow anaesthesia techniques
How can we minimise exposure to anaesthetic?
-all connections must be airtight
-endure patient connected before turn on volatile agent
-minimise use of masks
-good ventilation
-service equipment
What is the APL valve?
-safety feature
-must check position of valve before attaching patient
How to calculate FGF?
TV = weight x 10-15ml
(Use 15ml for animals under 10kg)
MV = TV x resp rate
FGF = MV x circuit factor
What are advantages of using non-rebreathing circuits?
-cheap
-simple construction for cleaning
-soda lime not required
-low resistance
What are disadvantages of using non-rebreathing circuits?
-high carrier gas flow required, expensive
-high volatile agent consumption, expensive
-expired moisture and heat lost
When is ayres t piece used?
-animals under 10kg
-suitable for IPPV
CF = 2.5-3
When is Bain used?
-animals over 10kg
-suitable for IPPV
CF = 2.5-3
When is MaGill used?
-animals over 10kg
CF = 1-1.5
When is lack used?
-animals over 10kg
-mini lack under 10kg
-not used IPPV
CF = 1-1.5
What are advantages of rebreathing circuits?
-lower fresh gas flow rates required, cheap
-lower volatile agent consumption, cheap
-expired moisture and heat conserved
What are disadvantages of rebreathing circuits?
-high resistance
-expensive
-soda lime must be replaced regularly
When is circle used?
-animals over 10kg
-suitable IPPV
What does soda lime do?
-colour change to indicate exhaustion which varied between manufacturer
What are requirements for anaesthetic chambers?
-must be durable and airtight
-ideally transparent to allow observation of patient
-should have gas inlet and scavenging outlet
-only used when necessary
What are safety checks for circuits?
-correctly assembled
-if APL correct position, opened
-any kinks, cracks or dirt
-tested for leaks
-connections must be airtight
