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Patient Monitoring and Instrumentation > Principles of the Anesthesia Machine Part 1 > Flashcards

Principles of the Anesthesia Machine Part 1 Flashcards

Slides 1-106

1
Q

What is blood pressure?

A

the measurement of force applied to artery walls; a practical method for addressing tissue perfusion

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2
Q

What is normal blood pressure?

A

120/80

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3
Q

What blood pressure is high and it’s name?

A

hypertension (HTN) greater than or equal to 140/90

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4
Q

What blood pressure is low and it’s name?

A

hypotension (hTN) less than or equal to 90/60

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5
Q

What is mean arterial pressure?

A

MAP shows diastolic effects MAP twice as much as systolic because it’s twice as long

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6
Q

What is the equation for MAP?

A

MAP=[(2)(Diastolic BP)+Systolic BP]/3

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7
Q

What is the MAP for a patient with a BP of 125/85

A

MAP= 98.3 mmHg

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8
Q

What is pulse pressure?

A

systolic pressure minus diastolic pressure

normal pulse pressure = 30-40mmHg

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9
Q

When is pulse pressure narrow?

A

when it is <25% of systolic BP

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10
Q

When is pulse pressure wide?

A

when it is >50% of systolic BP

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11
Q

What is hypertension?

A

High BP; it may lead to atherosclerosis or heart failure; thickened wall of blood vessel

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12
Q

What are the 4 consequences of hypertension?

A

1- strain to the heart (left ventricle enlargement)
2- increased oxygen demand
3- possible stroke
4- decreased tissue organ perfusion

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13
Q

What are the factors that affect BP?

A

1- blood volume (hypovolemia)
2- vascular tone (vasodilation causes low BP; vasoconstriction causes high BP)
3- medication (vasodilators & vasoconstrictors)

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14
Q

Vasodilators

A

decrease BP by peripheral vasodilation

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15
Q

Vasoconstrictors

A

increase BP by peripheral vasoconstriction thus increasing blood flow to vital organs

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16
Q

What does an EKG ( or ECG) measure?

A

the electrical activity of the heart

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17
Q

What are normal, fast and low EKG?

A 
normal= 60-100
fast= greater than 100
slow= less than 60
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18
Q

What does the Pulse Oximeter (SpO2) measure?

A

the % of hemoglobin that is saturated with oxygen

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19
Q

What is a normal SpO2?

A

93-98%

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20
Q

What is end tidal CO2 (EtCO2)?

A

the amount of CO2 in expired air

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21
Q

What is normal EtCO2?

A

35-45mmHg

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22
Q

What is a capnograph and its two functions?

A

EtCO2 monitor
1- reveals EtCO2
2- reveals Respiratory Rate

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23
Q

What are normal respiratory rates? Spontaneous? Ventilator?

A 
Spontaneous= 12-20 
Ventilator= 8-12
Pain= increases RR
Narcotic= lower RR
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24
Q

What is a normal body temperature?

A

36-38 degrees celsius

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25
Q

Take a moment and sketch the anesthesia machine pathway

A

check with picture from PPT

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26
Q

What are the two purposes of the anesthesia machine?

A

1- allow positive pressure ventilation (bag or ventilator)

2- allow us to deliver anesthetic gases to keep patients asleep

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27
Q

What are the two types of anesthesia gases?

A

1- Volatile agents (iso, sevo, des); keep patients asleep, found in vaporizer
2- Fresh gas flow (FGF) gases (air, O2, N2O); come from wall and carry vapors to patients

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28
Q

How many volatile agents can be used at once?

A

1

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29
Q

What is atelectasis ?

A

collapsing of the aveoli/lung

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30
Q

What is FiO2?

A

fraction of inspired oxygen

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31
Q

What is apnea?

A

cessation of breathing

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32
Q

Why do we use oxygen as a FGF? (3 Things)

A

1-the increase in FiO2 compensates for atelectasis
2- some patients (COPD, lung disease) need increased FiO2 to have adequate oxygen saturation (SpO2)
3- in case of apnea at the end of surgery

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33
Q

Why use nitrous oxide as a FGF? (2 things)

A

1- has analgesic properties (ONLY ONE)

2- allows lower use of volatile agents

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34
Q

Why use air as a FGF? (3 things)

A

has lower FiO2
1- too much oxygen could be toxic (relevant for children)
2-high FiO2 could cause absorption atelectasis
3- An FiO2 above 30% increases the risk of airway fire

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35
Q

What is a flowmeter?

A

Where the FGF gases are held and can be delivered by turning the flow control valves

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36
Q

Can multiple FGF gases be delivered at once?

A

Yes

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37
Q

What is the maximum amount in Liters can a flowmeter deliver to the patient in 1 minute?

A

15Liters

38
Q

What carries the volatile agents to the patient?

A

Fresh gas flow gases

39
Q

How do you supply the vaporizer the volatile agents?

A

They are in liquid form and they pour into the vaporizer

40
Q

What are the two sources that supply the FGF gases to the machine?

A

1- Wall supply (endless); (H cylinders)

2- E cylinders tanks(limited, for backup)

41
Q

What is the green hose for?

A

oxygen

42
Q

What is the blue hose for?

A

nitrous oxide

43
Q

What is the yellow hose for?

A

air

44
Q

What is the purple hose for?

A

scavenging

45
Q

What do the wall supply hoses connect?

A

the wall supply to the machine

46
Q

What is the pressure of FGF gases in the H cylinders?

A

2,000psi

47
Q

What is the pressure of FGF gases in the wall supply hoses?

A

50psi

48
Q

What is the pressure of the FGF gases in the machine?

A

16psi

49
Q

Is the pressure high or low in the E cylinders?

A

high (up to 2,000psi for oxygen and up to 750psi for nitrous oxide)

50
Q

Are E cylinders a part of the high pressure or low pressure pathway?

A

High pressure pathway

51
Q

What is the pressure of a FGF gas after it leaves the tank?

A

~45psi

52
Q

Why does the anesthesia machine use the wall supply over the E cylinders?

A

The machine preferentially chooses the highest pressure. 50psi (wall).

53
Q

What must the anesthetist do to switch from wall supply to E cylinders?

A

unplug the wall supply hoses and open up the E cylinders

54
Q

What reduces the FGF gases from 50psi to 16psi?

A

2nd stage regulator

55
Q

What are the 10 steps in the low pressure pathway?

A 
1- flowmeters
2- common manifold
3- vaporizers
4- common gas outlet
5-inspiratory tubing
6- patient
7- expiratory tubing 
8- rebreathing bag or ventilator
9- CO2 absorber and APL valve
10- exhaled gas rejoins the common gas outlet (some goes back to patient and some goes to the scavenging system)
56
Q

What are the two things the scavenging system does?

A

1- removes excess gas from circuit

2- prevents pressure build up

57
Q

What should the scavenging system be set at?

A

10-15L/min

58
Q

What valve controls how much gas goes into the scavenging system?

A

the APL valve

59
Q

What are the 3 things that the APL valve allows adjustment of?

A

1- amount of FGF going to scavenging
2- amount of gas patient rebreathes
3- amount of pressure in circuit

60
Q

What are the options for delivering positive pressure ventilation (PPV)?

A

1- bag

2- ventilator

61
Q

Why do anesthetists want pressure in the system?

A

to be able to deliver positive pressure ventilation

62
Q

What does opening the APL valve cause?

A

increase in volume to scavenging

decrease the volume and pressure in circuit

63
Q

What does closing the APL valve cause? (not all the way)

A

decrease the volume to scavenging

increase the volume and pressure in circuit

64
Q

What happens when the APL valve closes all the way?

A

patient is rebreathing all of their exhaled gas

the volume and pressure in the circuit can become dangerously high

65
Q

Why would you ever close the APL valve?

A

difficult time sealing the mask (a leak)

66
Q

True/False The APL valve should normally be partially open?

A

True; this allows the right amount of pressure to build up in circuit but not too much

67
Q

Why would the APL valve be all the way open?

A

patient is breathing spontaneously

68
Q

What are the 4 possibilities of a leak?

A

1- mask leak
2- circuit becoming disconnected from machine or ETT
3- deflated ETT cuff
4- leak in machine

69
Q

What are the two things that the high pressure pathway of oxygen powers?

A

1- ventilator

2- oxygen flush valve

70
Q

Does the high pressure oxygen go through the ventilator into the patient?

A

No, the high pressure oxygen is applied EXTERNAL to the ventilator bellows

71
Q

What does pressing the oxygen flush valve do?

A

rapid increase the circuit pressure (50psi)

rapid increase in circuit volume (35-75L/min)

72
Q

Why would you use the oxygen flush valve?

A

When there is a leak in the circuit (beard or difficult mask seal)

73
Q

What will the pressure gauge read when the APL valve is open?

A

Zero

74
Q

Will the pressure in the system increase or decrease when the anesthetist delivers a positive pressure breath?

A

Increase

75
Q

What are vascular pressures measured in?

A

mmHg

76
Q

What are airway pressures measured in?

A

cmH2O

77
Q

What should the airway pressure be when mask or LMA ventilating?

A

do not exceed 20cmH2O

*going over could get air in the stomach

78
Q

What should the airway pressure be when ETT ventilating?

A

do not exceed 40cmH2O

*going over could cause trauma to the lungs

79
Q

What are the 4 ways to get pressure in the system?

A

1- turn on FGF gases
2- close the APL valve
3- push the oxygen flush button
4- avoid leaks in the system

80
Q

What does the bag do when the patient exhales?

A

breathing bag expands

81
Q

Is the ventilator a part of the circuit when in bag mode?

A

No

82
Q

What are the 3 ventilation options in bag mode?

A

1- spontaneous ventilation (APL valve open)
2- mechanical ventilation (PPV; APL valve partially open)
3- Assisted ventilation (partially close APL valve, squeeze bag when patient is inhaling)

83
Q

Why would a patient cough on a ventilator?

A

they are trying to breathe spontaneously

84
Q

What are the ways to tolerate the ventilator?

A

needs to abolish the patients respiratory drive
1- muscle relaxant (long term)
2- narcotic (long term)
3- propofol (short term)

85
Q

What is a Thorpe tube?

A

the tube found in the flowmeters, wider at the top narrow at the bottom

86
Q

What is considered a low flow?

A

Less than or equal to 1L/min

87
Q

What is considered a high flow?

A

up to 15L/min

88
Q

Why is the Oxygen downstream from nitrous oxide in the flowmeter?

A

it prevents a hypoxic mixture from going to the patient (leaks in the PPT)

89
Q

What is the flowmeters mechanical proportioning system?

A

built in system that limits the percent of nitrous oxide that can be given to a patient. 3:1 is the max ratio

90
Q

What is the minimum oxygen concentration allowed with nitrous oxide?

A

25%

Patient Monitoring and Instrumentation (24 decks)

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