Anaesthetic machine

Question 1

What are the 3 roles of the anaesthetic machines?

Answer 1

1. artificial atmosphere which is delivered to the patient
2. To maintain general anaesthesia by mixing the general anaesthesia with fresh gas flow
3. emergency life support by IPPV

Question 2

What kind of machines are there?

Answer 2

1. portable machines
2. wall-monitored units
3. complex units

Question 3

What is the most NB function of the anaesthetic machine?

Answer 3

1. supply of gas
2. measurement of gases
3. anaesthetic vaporisers
4. breathing circuits
5. use as resuscitation apparatus

Question 4

Which gases are liquid when compressed in cylinders?

Answer 4

1. Nitrous oxide
2. CO2
   You need to weigh them to determine whether they are empty or full

Question 5

Which gases are still gases in the cylinders?

Answer 5

1. Air
2. nitrogen
3. oxygen
   The pressure inside gives an indication of what’s going on in the cylinder

Question 6

What happens when the oxygen runs out?

Answer 6

A ritchie whistle will blow

Question 7

What is the minimum amount of oxygen that can be delivered during anaesthesia?

Answer 7

30%

Question 8

What is the reason for giving 30% of oxygen?

Answer 8

-There is an increase of ventilation and perfusion mismatch during general anaesthesia

Question 9

What is fresh gas flow?

Answer 9

It is when there is a continuous supply of a minute volume of fresh gas to the patient

Question 10

What does minute volume consist of?

Answer 10

Tidal volume and x frequency

If the patient is under mechanical ventilation then 8mg.kg delivered at 9 breaths per minute is fine

Question 11

What are flow meters?

Answer 11

Flow meters are tubes that have measures of selected gases that have a plastic ball or arrow above

Question 12

Where is the anaesthetic gas contained in? And what is NB about the vaporiser?

Answer 12

A vaporiser
There are multiple vaporisers on the machine and we cannot open many of them at a time because it leads to contamination of the downstream vaporiser

Question 13

What is the splitting ratio?

Answer 13

The anaethetist is able to adjust the dial on the vaporiser and determine how much of the fresh gas flow contains the anaesthetic drug and how much does not

Question 14

What is the emergency oxygen given to the patient?

Answer 14

It is oxygen that does not have the anaesthetic drug and is up to 20 litres.min
If it is left open for long enough it will lead to the patient waking up

Question 15

What are the 2 breathing systems?

Answer 15

1. Rebreather

2. Non-rebreather

Question 16

How does the rebreather system work?

Answer 16

1. The gas that is not used up by the patient is used up again and oxygen is added to the mix
   There is a chance of CO2 accumulation in which a CO2 absorber is utilised

Question 17

Where does the expired gas from a patient go?

Answer 17

It goes outside of the operating room

Question 18

At what measurement should a functional suction apparatus read after 1 minute?

Answer 18

400-600 cm H20 pressure

Question 19

What is important about having an ambubag closeby?

Answer 19

It is essential to have positive pressure ventilation to compensate for if the oxygen cannot be administered by the machines for some reason

Question 20

What is the main breathing system used?

-What does it have attached?

Answer 20

Ayres T piece or the Mapleson E

• P= patient
• F= fresh gas flow
• R= reservoir

Question 21

What is the modification with the reservoir bag and the Ayres T piece?

Answer 21

The Jackson-Rees modification

Question 22

What is another name for the spring loaded valve mechanism?

Answer 22

Mapleson D system

Question 23

How do we ensure that the fresh gas flow is at a high enough rate to get tp the patient?

Answer 23

Increase the rat to approximately 2.5-3 times the patients predicted resting minute volume

Question 24

What is another name for the Magill’s breathing system?

Answer 24

Mapleson A- this has a spring valve a or close to the patient’s mouth

Question 25

Which system is best for controlled ventilation and not spontaneous ventilation?

Answer 25

T piece system

Question 26

Which system is best for spontaneous ventilation and not controlled ventilation?

Answer 26

Magills breathing system

Question 27

What is the Bain’s system?

Answer 27

Mapleson D

-It has fresh gas flow running through the large resevoir tube and is a coaxial system

Question 28

What is the fresh gas flow that is needed for spontaneous ventilation that is required for the T-piece?

Answer 28

-2,5 to 3 times of the patients minute volume

Question 29

What is the fresh gas flow needed for controlled ventilation?

Answer 29

1 times the minute volume of the patient

Question 30

Which patients do we usually use the Ayres T piece in?

Answer 30

-Children less than 20 kilograms

Question 31

What are the disadvantages of using the T-piece?

Answer 31

• It wastes fresh gas flow if spontaneous breathing is applied
• the bag/ventilator may get twisted and stop breathing

Question 32

What are the advantages of the Ayres T piece?

Answer 32

• It is economical for controlled ventilation
• minimal dead space
• low work of breathing

Question 33

What are the 3 possible causes of ETC02 of 0mmHg?

Answer 33

• tube in the oesophagus
• cardiac arrest with prolonged downtime
• spontaneous apnea

Question 34

What is the DOPE pneumonic in regards to ETC02 reading 0mmHg?

Answer 34

D-dislodgement
O-obstruction
P-pneumothorax
E-equipment