The anaesthetic machine

Question 1

Gas supply

Answer 1

• Piped
• Gas cylinders
• Or both
• Described as a pressurised container used for storage and transport
• The gases used in anaesthesia are generally supplied under high pressure, either in cylinders or anaesthesia machines for emergency backup

Question 2

Gas container colours

Answer 2

• Oxygen = black with white top
• Nitrous oxide = blue
• Medical air = grey with black top and white stripe

Question 3

Pin index safety system

Answer 3

• Each cylinder type has a specific pin position that match with the machine of the delivery system it’s designed for

Question 4

Oxygen generator

Answer 4

• Used to generate oxygen in practice instead of using piped or gas cylinder oxygen

Question 5

Pressure gauge

Answer 5

• Provides info on the gas left in the cylinder or pipeline gas supply
• Should be checked before using anaesthetic machine as a part of equipment checklist
• Pressure gauges don’t give reliable info for nitrous oxide levels as this is a liquid in the cylinder and therefore will need to be weighed

Question 6

Pressure reducing valve

Answer 6

• Reduce the pressure coming from the gas coming from the cylinder and maintain a constant pressure to prevent any surge in the pressure being relayed to the patient
• They are only present in an anaesthetics machine that has gas cylinders attached directly to the machine
• Where pipelines are used the regulator will be at the source of the gas

Question 7

Flowmeter

Answer 7

• Provide final stage in the reduction of the pressure of gas and they allow manual adjustment of the volume of gas delivered to the patient
• Contained in the flowmeter is a bobbin which will spin/move by the gas and it moves around it
• When setting a flow rate for a patient the top of the bobbin or the white dot on the bobbin is used depending on what is available on the anaesthetic machine you use

Question 8

Emergency oxygen flush

Answer 8

• This provides oxygen directly from the cylinder or pipeline, bypassing the vapouriser
• Care should be taken when using this function as the oxygen is delivered at high flow rates that could cause trauma to the patient

Question 9

Oxygen failure alarm

Answer 9

• This sounds if there is a drop in pressure of the oxygen supply
• This is an extremely important safety feature

Question 10

Mini-Schrader sockets

Answer 10

• Gas sockets that provide oxygen or air to power ventilators
• Schrader probe - connects to the socket and prevents the misconnection to the wrong gas socket

Question 11

Transportation of oxygen through anaesthetics machine

Answer 11

1. Oxygen enters machine at lower, back of flowmeter
2. Oxygen exits the flowmeter
3. Oxygen enters the vapouriser, collects the anaesthetic agent
4. Oxygen agent mixture exits the vapouriser
5. Gas and agent enters breathing bag and inhalation tube and is inhaled by patient

Question 12

Vapouriser

Answer 12

• The majority used in the UK are temperature compensated vaporisers
• They automatically compensate the temperature changes to ensure maintenance of a constant concentration of inhalation agent in the delivered gas mixture