Anesthetic equipment

Question 1

What are the two functional systems of the anesthetic machine

Answer 1

Life support- oxygen and everything associated with breathing and assisted ventilation
Inhalant drug delivery- getting a safe amount of gas into the patient to keep them under

Question 2

What are the basics continuous machine designs

Answer 2

High pressure system
Intermediate pressure system
-Flow metres
Low pressure system

Question 3

What are high pressure anaesthetic machines

Answer 3

High pressure supply of gasses (supplied by cylinders or pipelines)
Pressure gauges (regulators) to control flow of gasses into the machine

Question 4

What is the low pressure anaesthetic machine

Answer 4

Vaporizer to create accurate mix of gasses at known concentration
Breathing circuit- to deliver to patient

Question 5

What is the flow through a bane anaesthetic machine

Answer 5

Tank
Tank pressure gauge
Pressure reducing valve
Line pressure gauge
Flow meter
Vaporizer
Patient
Excess into charcoal canister

Question 6

What is the flow of anaesthetic in a rebreathe system

Answer 6

Tank
Tank pressure gauge
Pressure reducing valve
Line pressure gauge
Flow meter
Vaporizer
Inhalation valve
Y-piece
Patient
Exhalation tube
CO2 canister
Pressure manometer
to scavenger

Question 7

High pressure system is used for

Answer 7

O2 N2O

Question 8

High pressure system can have what oxygen supply

Answer 8

Pipeline or cylinders

Question 9

pipeline oxygen supply for high pressure systems are

Answer 9

50 psi (same as normal working pressure of most machines)
Tanks are located elsewhere in building

Question 10

Cylinder in a high pressure system is

Answer 10

Oxygen is supplied around 2000 psi (needs to be reduced to about 45 psi when entering anaesthetic machine)

Question 11

What is a yoke assembly

Answer 11

Hanger yoke assembly- connects cylinder to machine; ensures unidirectional gas flow; creates seal b/w cylinder and machine

Question 12

Pin index system is

Answer 12

Used with E-cylinders
Medical gasses to ensure correct cylinder is being fitted to yoke
Pins in yoke assembly match to holes in a specific cylinder– ensures correct gas is being used
Do not change/move safety pins; check pins; keep cylinder attached to prevent pin damage

Question 13

Cylinder pressure gauge and regulator is

Answer 13

Gauge measures gas pressure in tank
Pressure is read when tank is turned on
Regulator reduces pressure form as high as 2200 PSI to 45-60 PSI

Question 14

Oxygen tanks can be what colour

Answer 14

White
Green
White + green
White + black (UK, Europe)

Question 15

N2O tanks are what colour

Answer 15

Blue

Question 16

Intermediate pressure systems have

Answer 16

O2 flush valve
O2 flow meter assembly
O2 alarms

Question 17

O2 flush valves for intermediate pressure systems are

Answer 17

Direct tube that connects the O2 source to the breathing circuit (bypasses vaporizer)
Gives 35-70 L/min flow (40-60 psi) of pure oxygen as a “straight shot”
Can be used to flush aesthetic agent from lines
Never use with a Baine
Too high pressure can cause pressure damage to small animals
Can ignore and obtain similar effect by turning up oxygen flow meter

Question 18

O2 flow meter assembly of intermediate system

Answer 18

Controls, measures and indicates rate of flow of gas passing through it
Control knob is colour coded for each gas (white=O2; blue=N2O)
Opening stem increases flow rate; closing decreases rate
Specific for each machine and calibrated for 20*C, 101.3 kPa

Question 19

How to correctly read a flow meter

Answer 19

Read from TOP of bobbin; MIDDLE of ball

Question 20

O2 alarms are in what machines and do what

Answer 20

Standard in newer machines
Alarm sounds if too high pressure, sustained high pressure or negative pressure detected

Question 21

Low pressure system is located where

Answer 21

Everything located downstream of the flow meter

Question 22

Vaporizer is and used for

Answer 22

Aka precision plenum vaporizer
Delivered a set partial pressure of inhalant gas; and mixes with oxygen
Vaporizers are specific to one anaesthetic gas (based on vapour pressure; note colour coding)
Has lock and key system that matches anaesthetic bottle to ensure only one agent used
SVMA byways vaporizers must be serviced every 2 years (recommended every year)

Question 23

Why cant you tip the vaporizer

Answer 23

Liquid anaesthetic gas may enter lines= unpredictable amount of gas delivered to patient next time it is used
If tipped have machine services prior to next use

Question 24

What colour does each vaporizer indicate

Answer 24

Halothane = red
Isoflurane = purple
Sevolflurane = yellow
Desflurane = blue

Question 25

Common gas outlets are

Answer 25

Where the mixture of oxygen and inhalant are delivered into the breathing system
Usually has a valve that allow switching between non-rebreathing and rebreathing circuits

Question 26

pop off valve is and used for

Answer 26

AKA APL valve, exhaust valve
Pressure relief valve
Allows excess gas to escape the system
Opens at a pressure of 5 psi
Prevents damage to the vaporizer and flow meters if there is outlet obstruction
Keeping closed will cause pressure system to build
Always keep open
Always check to make sure it is not obstructed
Only close to manually ventilate or if auto-ventilating

Question 27

What happens if you keep the pop off valve closed

Answer 27

Keeping closed will cause pressure system to build
Patient cant breathe
Barotrauma

Question 28

Rebreathing bag is

Answer 28

Reservoir bag-patient breathes from the bag
You want the bag to be big enough to fill patients lungs during an inhalation, but not so large that you can’t visualise respiration
Size determination based roughly on weight of the patient (using tidal volume)

Question 29

How is the rebreathe bag useful

Answer 29

As patient draws from bag, can use to
Monitor resp rate
Monitor depth of breathing
Ventilate

Question 30

What does the rebreathe bag size do

Answer 30

Comes in a variety of sizes- 300ml to 35L (LA)
Size is indicated on bag
Need to be rinsed with soapy water and hung to dry between every patient

Question 31

Soda lime (calcium and sodium hydroxide) is used for

Answer 31

Specific to removing CO2 from a rebreathing circuit (so patient is not breathing in the excess CO2)
Exhaled gas flows through one way valve to CO2 canister → scavenger (ie. soda lime) selectively absorbs CO2 that was breathed out→ oxygen and inhalant gas that was not absorbed continuous to patient or exhaust
Only used in rebreathing system (circle) system

Question 32

When should you change the soda lime

Answer 32

Increased CO2 build up in patient
Colour change
Lack of heat in canister
Harness of granules (dried out granules don’t absorb)
Time in function
Gain of 50g in canister (weight before attaching to machine)

Question 33

How can the capnograph let you know the soda lime needs to be changed

Answer 33

Base line will be above 0

Question 34

Why does the colour of soda lime change and when is this helpful

Answer 34

Colour change is with pH indicator
Change when ⅔ canister has changed colour
Not reliable on its own because
Only works when granules are “packed properly”
Reverts to white if not used for a while

Question 35

Waste anesthetic gas is

Answer 35

Personal safety concern
Nitrous oxide, halogenated anesthetic gasses, metabolic by-products of anaesthetic gasses
Measured in parts per million (ppm)
Number of molecules of iso per 1 million molecules of air

Question 36

What is waste anesthetic gas controlled by

Answer 36

Avoiding spills
Testing equipment for leaks
Exhaust and scavenging of WAGs

Question 37

What does the waste anaesthetic gas scavenger do

Answer 37

Scavenger remove waste anesthetic gasses from work space
Attaches at pop-off valve (rebreathing) or tail of reservoir bag (nonrebreathing)
Collects gas leaving circuit and
Disposes it outside the building (active or passive system)
Or
Gasses through activated charcoal canisters before releasing into room air
Activated charcoal scavenging canister on anaesthetic machine
Exhaust system with or without charcoal system attached

Question 38

Why is activated charcoal used as a gas scavenger

Answer 38

Convenient
Requires frequent replacement (q 12h or gain of 50g)
Works best with higher pressure air flow
Different form soda lime which only removes CO2

Question 39

What do you do to scavenge waste aesthetic when not using charcoal

Answer 39

Can be active (fan moves air) or passive (pushed out by pressure placed into system)
If blocked, will prevent gas leaving circuit (same as if leaving pop-up valve closed)

Question 40

Patient rebreathing system allows what

Answer 40

Allow cyclic flow
To and from the patient
Aka breathing

Question 41

3 types of breathing systems

Answer 41

Open circuit ventilation system
Non Rebreathing circuit (includes Bain)
Rebreathing circuit (aka circle system)

Question 42

Open circuit breathing system does what

Answer 42

Gas is from atmosphere alone
Ambu-bag

Question 43

Non rebreathing circuit works by

Answer 43

All exhaled gas is dumped (therefore no CO2 canister required)
Patient always get fresh gas flow (FGF)
Bain coaxial circuit is most common in vet med

Question 44

When and why is the non rebreathing circuit used

Answer 44

Used in small patients <10 kg (must use if less than 3kg)
Less dead space and resistance to breathing which is preferred
Fresh gas port goes directly to patient; exhaled gas goes to the reservoir bag (past open pop-up valve), then out of the machine
Does not require soda lime
Requires higher O2 flow rates to push expired gasses down exhaust tube

Question 45

Rebreathing circuit is

Answer 45

Aka circle system; or semi-closed circuit
Some of the exhaled gas goes back to the patient
Operates using system of one way valves

Question 46

How does a rebreathing system work

Answer 46

Gas exits vaporizer → enters patient via FGF port→ patient exhales→ gas enters oneway exhaust port→ goes to reservoir bag→ excess pressure released from pop-off valve→ air from reservoir bag is rebreathed by patient→ air goes past soda lime canister to remove CO2→ pickles up additional fresh gas before entering patient

Question 47

When do you use a rebreathing system

Answer 47

Typical hoses are used for patients over 10kg
There are pediatric hoses available fo 3-10kg
Not appropriate for <3kg

Question 48

Non rebreathing system basics

Answer 48

Ex. Bain
Air in → air out
All Co2 and inhalant exhaled
Each breath is fresh O2 and inhalant
Higher flow rates (~150 ml/kg/min)= increased cost
Less dead space
Less resistance to spontaneous breathing

Question 49

Rebreathing system basics

Answer 49

Ex. circle
Exhaled CO2 (some inhalant gas ) is captured
Majority of inhalant is rebreathed through the system
Lower O2 (~30 ml/kg/min) = decreased cost
Use with >5kg patients
Getting more common
Conserves temp and humidity

Question 50

Flow rate with rebreathing system

Answer 50

Circle
Requires lower flow rate
O2 flow rate of 30 ml/kg/min

Question 51

Flow rate with non rebreathing systems

Answer 51

Bain
Requires higher flow rate
O2 flow rate of 150-200 ml/kg/min

Question 52

Adapter on systems are

Answer 52

Connect breathing tubes to endotracheal tube
Usually has an adaptor to capnograph (measured end-tidal CO2)

Question 53

Heat and moister exchanger is

Answer 53

Nice to have
Located between patient and circuit
Prevents moisture from entering the circuit while warming and humidifying gases to the patient.