Anaesthetic Equipment Flashcards
What colour were/are oxygen cylinders?
past - black bodies white shoulders
now - white with name on side
Which gas canisters will always read “full” on the guage unless empty? ie.no midway. How can you tell how much gas is left?
Nitrous Oxide
- weigh cylinder
What does medical grade air consist of? What colour is the cylinder?
Nitrogen mainly
- grey cylinder, black white quarters on top
What are the ends of pipelines called?
Schrader valves (colour coded like cylinders)
What are the disadvantages of oxygen concentrators?
- also produce water, mix with anaesthetic agent and can cause probems
- need a source of electricity
- max o2 conc 95%
What is the purpose of pressure regulators?
reduce cylinder pressure to safer level (4 bar) that wont explode animals lungs!
What are flowmeters calibrated for?
Individual gases
Which part of the bobbin or ball bearing is the flow rate read from?
centre of sphere, top of bullet
What units are flowmeters measuring in?
l/min
What does the emergency oxygen flush do?
Bypasses all pressureregulators etc. to purge system.. be careful!!
What warning system is often in pace to prevent inadequate oxygen delivery?
Pressure alarm whistles - if pressure drops below a threshold then air will escape the storage area and whistle
- the storage area must be filled when anaesthetic machine turned on so will whistle at start too
What are compressed O2 outlets for?
driving O2 powered ventilators at pressure
What are the 2 types of vaporisers?
TEC 3 and TEC 4 (anti spill feature)
- calibrated for one agent only
What environmental conditions must vaporisers account for?
temperature
- bimetallic strip regulates flow
What scavenging systems are available?
> Passive - dump outside window - charcoal absorber (replace every 12 hours, doesnt do NO) > Active - Vacuum systems - Need an air break to limit suction
What are the 2 main types of breathing systmes?
> Non- rebreathing systems
- Magill, Lack, Bain, Ayre, Humphrey
Rebreathing systems
- circle, to and fro
What is the Mapleson classifciation of breathing systems?
> functional classifcation A-E
- theoretical efficiency in fresh gas use
- fresh gas flow needed to prevent rebreathing expressed as a multiple of animals MINUTE VOLUME (tidal volume x resp rate)
= “circuit factor”
Calculating minute volume? Estimating in practice? How is total gas flow calculated from this?
- 10-15ml/kg (higher in small animals) x RR
- 200ml/kg/min for all domestic animals
- gas flow = CF x MV
What circuit factor does Magill have? What animals is this suitable for?
- 1-1.5 CF
- animals >10kg
What type of circuit is the coaxial lack basically the same as? What animals is it suitable for? CF?
- Magill
- > 10kg
- 1-1.5
What forms of parallell lack are available?
Standard animals >10kg
Mini animlas <10kg
Which patients is a T piece best for? CF?
Small (no valves, low resistance)
CF 2.5-3
What animals is a Bain suitable for? CF?
Animals >10kg (but uneconomical)
CF 2.5-3
- good for ventilating
How is the breathing system tested before use?
- connect machine
- close APL valve
- cover pateint end iwth thumb
- oxygen flush to inflate reservoir bag
- watch for leaks
- open APL valve
How are coaxial breathing systems checked?
- switch on O2 flow rate
- red stopper inserted
- if inner tube sealed, flow metre will drop
- if leaking, flow will remain constant
What is a Humphrey ADE?
Mapleson A, D and E in one device
- lever up = parallell lack or magill
- lever down = bain
Which machine have the vapouriser in circuit? Which are outside of circuit?
> in - komersaroff - stephens > out - circle - humphrey ADE - to and fro
What animals is a circle used for?
> 10kg
How does use of rebreathing circuits differ to non-rebreating circuits?
- when connecting animal to system, use higher fresh gas flow initially for 10 mins (2-4l/min or 100ml/kg/min)
- flushes air out of system to prevent silution of anaesthetic
What ratio of N2O:O2 should not be exceeded?
50:50
When should CO2 absorbant be changed?
When half of it has changed colour
- be aware colour may change back over night - does NOT mean it is safe to use again!
What may be produced by CO2 abdorbers?
carbon monoxide and compound a
What basis do in circuit vapourisers work on?
Patient regulates own level of anaesthtic gas
- if get light, breathing ^, more gas inhaled, gets deeper
- if get deep, breathing v, less gas inhaled, gets lighter
> very economical!
