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MODULE 14 - Patient Support > ANAESTHESIA - Anaesthetic Machine and Breathing Systems > Flashcards

ANAESTHESIA - Anaesthetic Machine and Breathing Systems Flashcards

1
Q

What are the four components of an anaesthetic machine?

A

Source of carrier gas
Flowmeter
Vaporiser
Scavenging system

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2
Q

Label the components of this anaesthetic machine

A
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3
Q

What is a carrier gas?

A

A carrier gas is a gas which delivers inhalational anaesthetic agents to your patient

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4
Q

What is the main carrier gas used in veterinary medicine?

A

Oxygen

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5
Q

Which three methods can be used to supply the carrier gas (oxygen)?

A
  • Oxygen stored in gas cylinders attached to the cylinder yokes at the back of the anaesthetic machines
  • Cylinder manifold system
  • Oxygen concentrator
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6
Q

Label the components of this cylinder yoke

A
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7
Q

Label the components of this oxygen cylinder

A
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8
Q

What is a cylinder manifold system?

A

A cylinder manifold system is a system of pipes and valves which connects a group of oxygen cylinders to wall outlets which the anaesthetic machine is connected to

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9
Q

How does an oxygen concentrator work?

A

An oxygen concentrator takes in room gas, removes the nitrogen and delivers purified oxygen to the patient

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10
Q

What colours are oxygen cylinders in the UK?

A

Completely white or a black body with a white shoulder

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11
Q

How do you measure the volume of gas left in an oxygen cyclinder?

A

When O2 is compressed into a gas cylinder, it remains a gas which means that there is a direct relationship between the pressure within the oxygen cylinder and the volume of oxygen. This means a pressure gauge can be used to determine the volume of oxygen in the cylinder

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12
Q

What are the two main safety features of the carrier gas supply to ensure you use the correct gas?

A

Everything is colour coded
Pin-indexing of the cylinder yokes and wall sockets

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13
Q

What is the function of the flowmeter?

A

The flowmeter allows you to control how much of the carrier gas (i.e. oxygen) is delivered to your patient

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14
Q

What is the function of the vaporiser?

A

The vaporiser converts the liquid anaesthetic agents into a vapour form and mix them with the carrier gas. This allows for precise control over the concentration of anaesthetic that the patient receives

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15
Q

Why is it so important to not tilt the vaporiser?

A

Tilting of the vaporiser could result in the delivery of extremely high anaesthetic concentrations due to the excessive flow of liquid anaesthetic into the bypass chamber

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16
Q

What is the function of the scavenging system?

A

The scavenging system removes waste anaesthetic gases exhaled by the patient from the operating theatre enviornment

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17
Q

What the two classifications of scavenging systems?

A

Passive scavenging system
Active scavenging system

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18
Q

Describe two examples of a passive scavenging system

A
  • Tubing attached to the APL valve which conducts the anaesthetic gas exhaled by the patient out of an open window
  • Tubing attached to the APL valve which conducts the anaesthetic gas exhaled by the patient into a cannister of activated charcoal
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19
Q

What are the two main benefits of a passive scavenging system?

A

Cheap
Portable

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20
Q

How does an active scavenging system work?

A

An active scavenging system typically consists of an extractor fan which creates a negative pressure in the scavenging system, drawing the excess anaesthetic gases into the scavenging system

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21
Q

What is the function of an air break receiver?

A

An air break receiver prevents the transmission of negative pressure exerted by an active scavenging system into the breathing system

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22
Q

Which four other methods can be used to limit the exposure of the operating staff to anaesthetic waste gases?

A
  • Good air conditioning
  • Avoid using face masks to deliver anaesthetic gases
  • Regular maintenance of the anaesthetic machines inclduing leak tests on the breathing system
  • Fill the vaporisers at the end of the day and use a key filler to limit exposure
A key filler
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23
Q

What is tidal volume (Vt)?

A

Tidal volume (Vt) is the total volume of air moved within one respiratory cycle

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24
Q

What is the average tidal volume (Vt)?

A

10 - 20ml/kg

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25
Q

What is minute ventilation?

A

Minute ventilation is total volume of air moved within one minute

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26
Q

What is the average minute ventilation?

A

200ml/kg

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27
Q

How do you calculate minute ventilation?

A

Tidal volume (Vt) x Respiratory frequency (f)

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28
Q

What are functions of breathing systems?

A
  • Deliver the inhalational anaesthetic and carrier gas to the patient
  • Remove exhaled carbon dioxide
  • Provide a means to provide intermittent positive pressure ventilation (IPPV) - by squeezing the bag
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29
Q

What is rebreathing?

A

Rebreathing is the rebreathing of either changed or unchanged air (containing carbon dioxide) during the subsequent breath

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30
Q

What is equipment dead space?

A

Equipment dead space is the volume of the breathing system that may contain exhaled gas which could be rebreathed during the subsequent breath

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31
Q

What are the three main components of a breathing system?

A

Tubing
Reservoir bag
Adjustable pressure monitoring (APL) valve

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32
Q

What are the two additional components which are not seen in all breathing systems?

A

Carbon dioxide absorbent
Unidirectional valves

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33
Q

Label the structures on this breathing system

A
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34
Q

What is the function of the tubing in the breathing system?

A

Tubing conveys anaesthetic gas to and from the patient

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35
Q

Why is the tubing congregated?

A

The tubing is congregated to reduce the risk of the kinking the tubing

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36
Q

Why has some tubing been adapted to only be congregated on the outside with a smooth inside?

A

To reduce resistance

37
Q

What is parallel tubing?

A

Parallel tubing is when two tubes run next to each other

38
Q

What is coaxial tubing?

A

Coaxial tubing is when one tube runs inside the other

39
Q

What are the three functions of the resevoir bag?

A
  • Reservoir to ensure a continuous suppy of gas for the patient
  • Provide a means to provide intermittent positive pressure ventilation (IPPV) - by squeezing the bag
  • Provides a visual indicator of patient ventilation
40
Q

What is the function of the adjustable pressure limiting (APL) valve?

A

The adjustable pressure limiting (APL) valve allows for the escape of excess exhaled gas into the scavenging system to regulate the pressure within the breathing system

41
Q

Describe the structure of the adjustable pressure limiting (APL) valve

A

The adjustable pressure limiting (APL) valve in an adjustable spring loaded disc valve with the tension on the valve modified by adjusting the valve top

42
Q

Describe how the adjustable pressure limiting (APL) valve works when the valve is open

A

When the valve is open, the tension on the spring is reduced which allows the slight increase in pressure caused by expiration to lift the disc which allows the exhaled air to enter the scavenging system

43
Q

Describe how the adjustable pressure limiting (APL) valve works when the valve is closed

A

When the valve is closed, the tension on the spring is increased which opposes the lifting of the disc, preventing the exhaled air from escaping

44
Q

(T/F) The adjustable pressure limiting (APL) valve can be open or closed during sponataneous ventilation

A

FALSE. The adjustable pressure limiting (APL) valve must always be open to allow for spontaneous ventilation

45
Q

When can the adjustable pressure limiting (APL) valve be closed?

A

The adjustable pressure limiting (APL) valve can be closed during intermittent positive pressure ventilation (IPPV) (squeezing the reservoir bag) but must be opened again to allow the patient to exhale

46
Q

What is one of the main signs of a closed adjustable pressure limiting (APL) valve?

A

The reservoir bag is extremely full

47
Q

What can occur if the adjustable pressure limiting (APL) valve remains closed when the breathing machine is attached to a patient?

A

Pneumothorax
Pneumomediastinum

48
Q

What is a non-rebreathing system?

A

A non-rebreathing system is where there is no rebreathing of exhaled gases due to the high fresh gas flow which flushes out the exhaled gas before the next inhalation

49
Q

What is the main advantage of a non-rebreathing system?

A

Due to the high fresh gas flow, the patient is inhaling fresh gas of a known composition which also allows for rapid changing of the anaesthetic depth

50
Q

What are the two main disadvantages of non-rebreathing systems?

A
  • High fresh gas flow has an increased cost and has an increased potential for enviornmental pollution
  • Fresh gas is cold and dry which contributes to hypothermia and respiratory dessication
51
Q

How do you calculate the fresh gas flow for a non-rebreathing system?

A

Multiply the ml/kg/minute values for the non-rebreathing system by the body weight of the patient (kg)

52
Q

What are the three types of non-rebreathing system?

A

Lack
T-piece
Bain

53
Q

What are the ml/kg/minute values for calculating the fresh gas flow for the different non-rebreathing systems?

A

Lack 150 - 200ml/kg/minute
T-piece 400 - 600ml/kg/minute
Bain 200 - 600ml/kg/minute

54
Q

What are the two classifications of the lack non-rebreathing system?

A

Parallel lack most common
Coaxial lack

55
Q

Which patients is the parallel lack appropriate for?

A

Patients 10kg or above

56
Q

What is the main disadvantage of a coaxial lack?

A

The can be damage/disconnection of the central tube which can result in rebreathing of carbon dioxide. This can be easily missed in a lack system

57
Q

What is the purpose of the minilack system?

A

The minilack system is a parallel lack adapted for smaller patients (less than 10kg)

58
Q

What are the three classifications of T-piece non-rebreathing systems?

A

Basic T-piece
Jackson-Rees modification T-piece
Mapleson D T-piece

59
Q

Which patients is the T-piece appropriate for?

A

Patients up to 10kg

60
Q

What are the features of a basic T-piece?

A

No APL valve
No reservoir bag

61
Q

What is the main advantage of a basic T-piece?

A

Due to having no APL valve, the T-piece has very low resistance so can be used in exotic work for very small mammals and birds

62
Q

What is the main disadvantage of a basic T-piece?

A

There is no reservoir bag so you cannot observe patient ventilation

63
Q

What is the Jackson-Rees modification?

A

The Jackson-Rees modification is the addition of an open ended reservoir bag at the end of a T-piece breathing system

64
Q

What are the advantages of the Jackson-Rees modification?

A

Allows for visualisation of patient ventilation
Allows for more controlled intermittent positive pressure ventilation (IPPV)

65
Q

What is the main disadvantage of the Jackson-Rees modification?

A

The Jackson-Rees modification is challenging to scavange, as the scavenging system is attached to the open end of the reservoir bag which can become twisted and prevent the gas from escaping

66
Q

What is the Mapleson D T-piece?

A

The Mapleson D T-piece is the addition of a closed reservoir bag and a paediatric APL valve to a T-piece breathing system

67
Q

What are the main advantages of the Mapleson D T-piece?

A

Adapted to facilitate scavenging
Has a paediatric APL valve so still has relatively low resistance

68
Q

What are the two classifications of the Bain non-rebreathing system?

A

Parallel Bain
Coaxial Bain most common

69
Q

Which patients is the Bain appropriate for?

A

Patients above 10kg

70
Q

What is the main disadvantage of a coaxial Bain?

A

The can be damage/disconnection of the central tube which can result in rebreathing of carbon dioxide. However, there is a way to test the integrity of the central tube in a coaxial Bain system

71
Q

Describe how to leak test the inner tube of the coaxial bain system

A
  1. Turn on the anaesthetic machine
  2. Set the oxygen flowmeter to 4-6L/min, reading from the top of the bobbin
  3. Briefly occlude the inner tube at the patient end using a syringe plunger
  4. If the inner tubing is intact, back pressure will cause the flowmeter bobbin to drop
  5. Be careful not to be forceful when occluding the inner tube as the force itself can slightly move the bobbin - giving a false reading
72
Q

(T/F) All of the non-rebreathing systems are sutiable for long-term intermittent positive pressure ventilation (IPPV)

A

FALSE. The Lack system is not sutiable for long-term intermittent positive pressure ventilation (IPPV)

73
Q

What is a rebreathing system?

A

A rebreathing system is when the exhaled gases are rebreathed however the carbon dixiode has been removed by a carbon dioxide absorbent. This allows for a lower fresh gas flow compared to a non-rebreathing system

74
Q

What are the two main advantages of a rebreathing system?

A
  • Lower fresh gas flow which is more econominal and reduces enviornmental pollution
  • The gases are warmed and humidified due to the exhaled air being rebreathed
75
Q

What are the three main disadvantages of a rebreathing system?

A
  • There is greater resistance due to the unidirectional valves and due to the exhaled gases having to pass through the CO2 absorbant cannister
  • Unsutiable for small patients
  • Patient inspires a mixture of fresh and exhaled gas so the composition of the gas will be unknown and thus it will take longer to alter anaesthetic depth
76
Q

Which substance is typically used as a carbon dioxide absorbant?

A

Soda lime

77
Q

What is complete rebreathing?

A

Complete rebreathing is when you provide the minimum fresh gas flow (i.e. just enough oxygen to meet the patient’s metabolic demand) to achieve complete rebreathing of exhaled gas and no release of gas via the APL valve

78
Q

What is the recommended fresh gas flow to achieve complete rebreathing?

A

10ml/kg/minute

79
Q

What are the main advantages of complete rebreathing?

A

Complete rebreathing is very economical and sustainable

80
Q

What is the main disadvantage of complete rebreathing?

A

The lower the fresh gas flow, the greater the discrepancy between the vaporiser setting and the inhaled breath. This is due to the dilutional effect caused by the volume of the fresh gas being much lower than the capacity of the breathing system

81
Q

What is partial rebreathing?

A

Partial rebreathing is when you provide a fresh gas flow greater than the required metabolic oxygens demands but less than the minute ventilation to achieve partial rebreathing and excess gas is released via the APL valve

82
Q

What is the recommended fresh gas flow to achieve partial rebreathing?

A

More than 10ml/kg/minute but less than 200ml/kg/minute

however for convenience most clinicians use a fresh gas flow of between 1 to 2 litres/minute

83
Q

What is denitrogenation?

A

Denitrogenation is the process of using a higher free gas flow for the first 10 -15 mins of anaesthesia to remove nitrogen from the breathing system as at the beginning of anaesthesia the breathing system will be full of room air

84
Q

What are the two classifications of rebreathing systems?

A

To & Fro system
Circle circuit

85
Q

What are the key features of a circle circuit system?

A

Soda lime cannister
Reservoir bag
Unidirectional valves

86
Q

Which patients is the circle circuit appropriate for?

A

Patients 10kg and over

87
Q

What is the Humphrey ADE Hybrid breathing system?

A

The Humphrey ADE Hybrid breathing system is a combination of the circle circuit, minilack and bain/t-piece breathing systems

88
Q

Describe how to leak test a breathing system

A
  1. First connect the breathing system to the anaesthetic machine
  2. Close the APL valve
  3. Place your thumb over the patient end of the system
  4. Press the oxygen flush button to fill the system with oxygen until the reservoir bag appears fully inflated
  5. Check for leaks via signs of deflation for 10 seonds. You can even give the bag a light squeeze
  6. Open the APL valve (do not remove your thumb until the APL valve is closed so you do not accidentally leave it closed)
  7. Remove your thumb

MODULE 14 - Patient Support (25 decks)

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