Anaesthetic Apparatus an Breathing systems

Question 1

cylinders

Answer 1

Different sizes
Treat with respect
Store under cover
Protect from extreme temperatures
Colour-coded for easy identification
Pin-index safety system (PISS) on E-size cylinders
sealing washer must be placed between cylinder + anaesthetic machine for a tight seal

Question 2

pipelines

Answer 2

Gas supplied from source outside building
Safer
More economical
fixed valves for set gases - schrader valves

Question 3

oxygen concentrators

Answer 3

Extract oxygen from air
Need a source of electricity (disadvantage)
Maximum O2 concentration ~95%

Question 4

anaesthetic machine

Answer 4

Gas supply 
Pressure gauges 
Pressure regulators 
Flowmeters 
Vaporizers 
Other features (emergency O2 flush, common gas outlet)

Question 5

pressure gauges

Answer 5

For oxygen, gauge pressure indicates amount
left in cylinder
For nitrous oxide, need to weigh cylinder

Question 6

pressure regulators

Answer 6

too much gas can damage the patients lungs
Reduce cylinder pressure to a safer level
(around 4 bar)
Keep pressure constant
Positioned between cylinders and machine

Question 7

flowmeters

Answer 7

Measure flow rates of gases
Calibrated for a single gas
Flow controlled by turning a knob on front of flowmeter
Knobs are colour-coded for each gas
Flow rate indicated by a bobbin or ball bearing floating in a transparent glass or plastic tube
Read flow rate from - TOP of bobbin, MIDDLE of ball bearing

Question 8

pressure release valve

Answer 8

if something blocks the outlet, the pressure does not rise so far that the machine comes apart! demonstrate its existence by blocking the outlet –watch the flowmeter fail, but not to zero

Question 9

vaporisers

Answer 9

Vaporise liquid (volatile) anaesthetics 
Deliver known concentrations of anaesthetic 
Calibrated for one agent only 
Accurate over a range of temperatures and flows
Efficiency of vaporization 
Temperature 
Time 
Gas flow rate 
Carrier gas composition

Question 10

isoflurane TEC 3

Answer 10

Agent specific filling - Fraser Sweatman pin
safety system, Prevents mixing of agents within the vaporizer
Must not be tipped over - Uncontrolled output of anaesthetic agent may result

Question 11

penlon vaporiser

Answer 11

Currently manufactured for isoflurane/sevoflurane 
Temperature compensated 
High resistance 
Agent specific 
Flow compensated 
Back pressure compensated 
Wick: cartridge design for easy cleaning

Question 12

Fraser Sweatman safety system

Answer 12

designed to reduce spillage of volatile agent and prevent mixing of two agents inside vaporiser

Question 13

Filling vaporizers - Sevoflurane

Answer 13

plug directly into vaporizer

Completely eliminates spillage

Question 14

scavenging systems

Answer 14

passive or active
Most breathing systems have a pop-off valve (APL or Adjustable Pressure Limiting valve)
Types of scavenging systems:
Activated charcoal absorbers - Must be replaced every 12 hours, Do not absorb nitrous oxide

Question 15

Anaesthetic Breathing Systems ‘Circuits’

Answer 15

Connect patient to anaesthetic machine 
Deliver oxygen 
Deliver anaesthetic gases 
Remove carbon dioxide from expired gas 
Provide means of ventilating animal

Question 16

non-rebreathing systems

Answer 16

CO2 removed by flow of fresh gas through the system: no expired gas is re-used
Suitable for animals >10kg
Flow rate 1-1.5 x minute volume (200300ml/kg/min)

Question 17

rebreathing systems

Answer 17

carbon dioxide in expired gas is removed by absorption so that expired gas can be re-used

Question 18

calculation of minute volume

Answer 18

Tidal volume – the volume of gas inspired or expired in one breath
Minute volume – the volume of air inspired or expired in one minute
Estimate tidal volume (TV) at 10-15ml/kg

Question 19

Lack system

Answer 19

Non-Rebreathing
Mapleson A
Co-axial (tube within a tube)
Parallel (standard and ‘mini’ versions)

Question 20

testing breathing system

Answer 20

Connect to anaesthetic machine
Close the APL valve (‘P’ means ‘Pressure’ i.e. closed)
Cover the patient end with your thumb.
Use oxygen flush to inflate the reservoir bag
Watch for leaks
OPEN APL VALVE
With co-axial systems it is important to check the inner tube also

Question 21

humphrey ADE

Answer 21

Universal circuit incorporating a lever which allows the circuit to be changed from a Mapleson A to D or E

Question 22

Rebreathing System - Advantages

Answer 22

By allowing rebreathing, much lower fresh gas flows are needed (economy)
Reaction of absorbent with CO2 produces heat and moisture

Question 23

Rebreathing System - disadvantages

Answer 23

Exact composition of inspired gas unknown
Changes in depth take longer
More expensive

Question 24

coaxial circle

Answer 24

rebreathing
“Universal F Circuit”
Inspiratory tube inside expiratory limb
Aids warming and humidification of inspired gases
Resistance increased slightly over parallel circle systems
Problems if inner (inspiratory) tube is cracked or becomes disconnected

Question 25

carbon dioxide absorbers

Answer 25

Soda Lime (potassium or sodium hydroxide)
pink to White
white to Violet
When it reacts with anaesthetic agent there is
Production of Carbon Monoxide and Compound A
Especially risk with very dry soda lime and sevoflurane or desflurane
“LoFloSorb” (Intersurgical) contains calcium hydroxide
which eliminates risks associated with Compound A and Carbon monoxide
Green to Violet (permanent colour change)

Question 26

vaporiser in-circuit

Answer 26

The vaporizer is located within a circle circuit
The patient breathes through the vaporizer
Must be low resistance vaporizer
An increase in ventilation will increase inspired anaesthetic agent concentration
A decrease in fresh gas flow rate will increase inspired anaesthetic agent concentration
Very economical in anaesthetic agent use: ideal for expensive agents such as sevoflurane
Very economical in oxygen use

Question 27

endotracheal tube

Answer 27

Made from red rubber, PVC or silicone 
Red rubber and PVC tubes have preformed curve 
Internal diameter marked in millimetres 
Check cuff before use 
Some have a ‘Murphy eye’