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APEX-Equipment > EQUIPMENT-Anesthesia machine > Flashcards

EQUIPMENT-Anesthesia machine Flashcards

1
Q

Where does the high-pressure system begin and end on the anesthesia machine

A 
Begins = cylinder
Ends= cylinder regulators
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2
Q

What are the 4 components of the high-pressure system

A
  1. Hanger yoke
  2. Yoke block with check valves
  3. Cylinder pressure gauge
  4. Cylinder pressure regulators
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3
Q

Where does the intermediate-pressure system being and end on the anesthesia machine

A 
Begin = at the pipeline
End = Flowmeter valves
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4
Q

What are the 7 components of the intermediate-pressure system

A
  1. Pipeline inlets
  2. Pressure gauges
  3. O2 pressure failure device
  4. O2 second stage regulator
  5. O2 flush valve
  6. Ventilator power inlet
  7. Flowmeter valves
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5
Q

Where does the low-pressure system begin and end on the anesthesia machine

A 
Begins = flowmeter tubes
Ends = common gas outlet
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6
Q

What are 4 components of the low-pressure system

A
  1. Flowmeter tubes (Thorpe tubes)
  2. Vaporizers
  3. Check valve
  4. Common gas outlet
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7
Q

What does the low-pressure leak test assess

A

The integrity of the low-pressure circuit from the flowmeter valve to the common gas outlet

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8
Q

How is a leak test performed

A

By attaching a bulb to the common gas outlet and creating negative pressure (-65 cm H2O)

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9
Q

When does a low-pressure system test fail

A

If the bulb reinflates within 10 seconds

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10
Q

What 5 things are prerequisites for a low-pressure system test

A
  1. The fresh gas flow must be off
  2. If there’s a minimum FGF when machine is on, the machine must be turned off
  3. The ventilator should be turned off
  4. The vaporizers should be off first, then test repeated with each one on
  5. It should be performed before the first case of the day
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11
Q

How is a high-pressure leak test performed

A

By closing the APL valve, pressurizing the circuit to 30 cmH2O and observing the airway pressure gauges, which should remain constant

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12
Q

What does a high-pressure system assess if the machine has a check valve

A

The breathing circuit and the low-pressure system up to the check valve
It does NOT assess for a leak between the check valve and the rest of the low-pressure system

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13
Q

What does a high-pressure system assess if the machine does NOT have a check valve

A

It assesses the breathing circuit and the entire low-pressure system

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14
Q

What is the SPDD model

A

Supply
Processing
Delivery
Disposal

It details the path gases flow as they enter the OR, travel through the machine and exit the OR

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15
Q

What is the supply component of the SPDD model

Where is this located

A

How the gases enter the anesthesia machine

Location = pipeline to the back of the anesthesia machine

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16
Q

What is the processing component of the SPDD model

Where is this located

A

How the machine prepares gases before they are delivered

Location = inside machine to the common gas outlet

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17
Q

What is the delivery component of the SPDD model

Where is this located

A

How the prepared gases are brought to the patient

Location = breathing circuit

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18
Q

What is the disposal component of the SPDD model

Where is this located

A

How the gases are removed from the breathing circuit

Location = scavenging system

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19
Q

What are the 5 tasks of O2 in the SPDD model

A
  1. O2 pressure failure alarm (intermediate-pressure)
  2. O2 pressure failure device (failsafe; intermediate-pressure)
  3. O2 flowmeter (low-pressure)
  4. O2 flush valve (intermediate-pressure)
  5. Ventilator drive gas
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20
Q

What is the PISS purpose

A

To prevent inadvertent misconnections of gas cylinders

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21
Q

What is the pressure change that occurs for O2 E-cylinder upon entering the intermediate system

A

Pressure of 1,900 psi drops to 45 psi ensuring that gas is preferentially pulled from the pipeline if the cylinder is left open

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22
Q

What is the PISS configuration for the following e-cylinders
O2
Air
N2O

A 
O2 = 2, 5 
Air = 1, 5
N2O = 3, 5
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23
Q

What is the purpose of DISS

A

Prevents inadvertent misconnections of gas hoses

Each gas hose and connector are sized and threaded for each gas

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24
Q

What is the pipeline pressure change that occurs at the DISS connection

A

50 psi, about the same as the intermediate system

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25
Q

What setting is are the cylinders on the back of the machine

A

OFF when not in use. This ensures if the pipeline pressure is lost, the failsafe alarm sounds and the cylinder isn’t empty

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26
Q

When should the E-cylinder gas be used

A

If pipeline pressure is lost

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27
Q

O2 E-cylinder:
Maximum pressure
Maximum volume
PISS

A

Maximum pressure = 1,900 psi
Maximum volume = 660 L
PISS = 2, 5

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28
Q

Air E-cylinder:
Maximum pressure
Maximum volume
PISS

A

Maximum pressure = 1,900 psi
Maximum volume = 625 L
PISS = 1, 5

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29
Q 
N2O E-cylinder:
Maximum pressure =
Maximum volume =
PISS = 
Full weight = 
Empty weight =
A 
Maximum pressure = 745 psi
Maximum volume = 1,590 L
PISS = 3, 5
Full weight = 20.7 lb
Empty weight = 14.1 lb
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30
Q

What state does O2 exist inside a cylinder and why

A

State = gas

Because its critical temperature is below room temperature (-119*C)

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31
Q

Which gas law is used to calculate cylinder gas contents

A

Boyle’s law

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32
Q

What is Boyle’s law

A

The pressure inside the cylinder is inversely related to its volume at a constant temperature

P = 1/V

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33
Q

How is the remaining gas volume in a cylinder calculated

A

[Tank capacity (L)] / [Full tank pressure (psi)]
x
[contents remaining (L)]/[gauge pressure (psi)]

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34
Q

How is the length of O2 supply calculated

A

Contents remaining(L)/FGF rate (L/min) = minutes before tank expires

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35
Q

The O2 gauge reads 500 psi. If the O2 flow is at 2 L/min, how long will the tank have until empty

A

87 minutes

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36
Q

The O2 gauge reads 600 psi. If the O2 flow is at 5 L/min, how long until the tank is empty

A

42 minutes

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37
Q

The O2 gauge reads 200 psi. If the O2 flow is at 3 L/min, how long until the tank is empty

A

23 min

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38
Q

What state does N2O exist inside a cylinder

A

Liquid

UNLESS it’s almost empty

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39
Q

Why does N2O exist as a liquid in a cylinder

A

N2O liquifies under high pressure

Its critical temperature is 36.6C which is above room temp (20C)

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40
Q

What is critical temperature

A

The highest temperature where a gas can exist as a liquid

The temperature above which a gas cannot be liquefied regardless of pressure

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41
Q

As N2O is exhausted from the cylinder, what happens to the pressure

A

It remains constant at 745 psi

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42
Q

When does the pressure of a N2O cylinder decrease.

How full is the tank at this point?

A

When all the liquid is consumed

It is 3/4 empty when the pressure is <745 psi

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43
Q

How much N2O (L) remains once the psi <745

A

400 L out of 1,590 L

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44
Q

What is the only reliable method to determine the volume of N2O that remains in the tank

A

Weight

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45
Q

What is the most delicate part of a cylinder and what can happen if damaged

A

The cylinder valve

Damage = missile

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46
Q

How should gas cylinders be stored

A

Upright position and secured

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47
Q

When is it acceptable to lay a gas cylinder on its side

A

Momentarily, when changing the cylinder on the machine

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48
Q

When opening a cylinder, a hissing sound is hear. What does this indicate and what are 4 troubleshooting methods

A

Indicates a leak

  1. Tighten connection
  2. Replace the washer between the cylinder and hanger yoke is #1 doesn’t work
  3. Use a different cylinder is #2 doesn’t work
  4. Do not place more than 1 washer between the cylinder and hanger yoke
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49
Q

Why should only 1 washer be used between the cylinder and hanger yoke

A

Using 2 washers can bypass the PISS and allow the cylinder to be hooked up to the wrong hanger yolk assembly

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50
Q

What happens if there is no cylinder or yoke plug present

A

Gas that should go to the patient will exit the machine

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51
Q

What components make up the fire triad

A
  1. Oxidizer
  2. Fuel
  3. Igniter
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52
Q

Where do O2 and N2O fit in the fire triad

A

They are oxidizers

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53
Q

At what temperature is the risk of fire or explosion of gas cylinders

A

> 130F or 57C

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54
Q

What is the purpose of the safety relief device

A

It there’s a fire, it opens allowing the cylinder to empty its contents slowly

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55
Q

What are 3 types of safety relief valves

A
  1. Fusible plug that melts at elevated temps (bismuth, lead, tin, or cadmium)
  2. A valve that open at elevated pressure
  3. A frangible disk that ruptures under pressure
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56
Q

Why is oiling a cylinder valve contraindicated

A

This increases the risk of fire by combining O2/N2O (oxidizers) with oil (fuel)

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57
Q

What is “cracking” a cylinder

A

The process of slowly opening the cylinder to flush the valve outlet clean of dust and debris

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58
Q

What are 4 agencies that mandate anesthesia machine component safety

A
  1. American society for testing and materials (ATSM)
  2. Food and drug administration (FDA)
  3. Occupational safety and health administration (OSHA)
  4. United states department of transportation (DOT)
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59
Q

What does the American Society for Testing and Materials monitor

A

Standards for the components of the anesthesia machine

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60
Q

What does the FDA mandate

A

Anesthesia machine pre-use checkout procedures

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61
Q

What standards does OSHA maintain with anesthesia

A

Sets the standards for acceptable occupational exposure to volatile anesthetics

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62
Q

What standards does the US DOT standardize

A

Standards for compressed gas cylinders

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63
Q

How often is a gas cylinder tested

A

Every 5 years

10 years with a special permit

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64
Q

What 7 items does the US DOT require on a cylinder label

A
  1. Government agency (DOT)
  2. Type of metal used to construct the cylinder
  3. Max fill pressure
  4. Serial number
  5. Manufacturer
  6. Owner
  7. Date of last inspection
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65
Q

What is the purpose of the O2 pressure failure device

A

To monitor for (and protect against) low O2 PRESSURE in the machine
It will alert if pipeline pressure is lost, disconnected O2 hose, or depleted O2 tank

It does not measure concentration

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66
Q

Which pressure system contains the O2 pressure failsafe device

A

Intermediate-pressure system

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67
Q

What are the 2 components of the O2 pressure failsafe device

A
  1. A threshold alarm sounds when the O2 pipeline pressure <28 - 31 PSI
  2. A pneumatic device reduces or stops N2O flow when O2 pipeline pressure is < 20 psi
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68
Q

How is the O2 pressure not truly a failsafe

A
  1. The failsafe only detects pressure. It would not detect if there was an O2-pipeline crossover and the incorrect hose was connected
  2. A leak in the flowmeter is upstream from the failsafe device
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69
Q

What does the hypoxia prevention safety device prevent

A

Prevents the user from setting a hypoxic mixture with flow control valves

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70
Q

When N2O is administered, what is the lowest FiO2 it allows

A

25%

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71
Q

What is the maximum ratio of N2O to O2 maintained by the proportioning device

A

3:1 (N2O:O2)

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72
Q

What are 4 situations that the hypoxia prevention safety device will no alarm

A
  1. O2 pipeline crossover
  2. Leaks distal to the flowmeter valve
  3. Administration of a 2rd gas
  4. Defective mechanic or pneumatic components
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73
Q

What is the difference between the O2 pressure failure device and the hypoxia prevention safety device

A

O2 pressure failure device monitors and responds to PRESSURE

Hypoxia prevention safety device prevents hypoxic mixture via proportioning the O2 and N2O

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74
Q

In what pressure system does the flowmeter reside

A

It begins the low-pressure system

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75
Q

What does the flowmeter control

A

The flow of gas that travels toward the vaporizer and common gas outlet

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76
Q

What 2 opposing forces determine the position of the flowmeter indicator float

A
  1. Fresh gas flow pushing float up

2. Gravity pulling float down

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77
Q

What are the 4 types of indicator floats and where is the measurement taken

A
  1. Skirted (top)
  2. Plumb bob (top)
  3. Nonrotating (top)
  4. Ball (middle)

Measurement is taken at the widest part of the float

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78
Q

What is the space called that lies between the indicator float and the sidewall of the flowmeter

A

Annular space

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79
Q

Describe the flowmeter internal diameter

A

Narrowest at base

Widens at top

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80
Q

Why is the geometry of the annular space important

A

It affects the flow pattern through the space

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81
Q

When the annular space is longer than it is wide
Where is the indicator=
What type of flow around float=
Flow dependent on gas=

A

Where is the indicator= lower in the tube (low flow)
What type of flow= laminar
Flow dependent on gas= viscosity

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82
Q

When the annular space is wider than its length
Where is the indicator=
What type of flow around float=
Flow dependent on gas=

A

Where is the indicator= Higher in tube (high flow)
What type of flow around float= turbulent (orificial)
Flow dependent on gas= density

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83
Q

What is Reynolds number for turbulent flow

Which law is this based on

A

Re > 4,000

Graham’s law

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84
Q

What is Reynolds number for laminar flow

What principle is this based on

A

Re <2,000

Poiseuille equation

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85
Q

Why is the order of flowmeters important

A

O2 must be closest to common gas valve and the patient, so it’s all the way to the right

This ensures if there is a crack in any of the other tubes, O2 will not leak causing a hypoxic mixture

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86
Q

What happens if there is a leak in the O2 flowmeter tube

A

A hypoxic mixture can be delivered

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87
Q

What is the equation for Reynolds number

A

(density x diameter x velocity)/viscosity

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88
Q

What is the FiO2 delivered if air is 2 L and O2 is 2 L

A

61%

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89
Q

What is the FiO2 delivered if air is 1 L and O2 is 3 L

90
Q

What is the total tidal volume delivered when fresh gas is coupled with tidal volume

A

Vt set on ventilator + FGF during inspiration - volume lost to compliance

91
Q 
When FGF is coupled to Vt, how are the following affected with increased FGF
Vt
Vm
PIP
EtCO2
A 
Vt = increase
Vm = increase
PIP = increase
EtCO2 = decrease
92
Q 
When FGF is coupled to Vt, how are the following affected by a decrease in FGF
Vt
Vm
PIP
EtCO2
A 
Vt = decrease
Vm = decrease
PIP = decrease
EtCO2 = increase
93
Q

Equation for compliance

A

(change in volume)/(change in pressure)

94
Q

How does circuit compliance affect the Vt a patient receives

A

During inspiration with PP, gas is lost to circuit expansion. The quantity of gas does not reach the pt

95
Q

Describe the variable bypass vaporizer

A

Fresh gas enters the vaporizer, some of the gas encounters the liquid anesthetic, the rest bypasses the anesthetic

96
Q

How is the amount of gas encountering the liquid anesthetic vs bypass determined

A

Setting the vaporizer dial to the desired concentration determines the splitting ratio of bypass gas and gas coming in contact with the anesthetic liquid

97
Q

How is 100% saturation of fresh gas inside the vaporizer chamber ensured

A

The fresh gas flows over a series of baffles and wicks, which increase surface area and turbulence, ensuring the fresh gas become saturated

98
Q

At what fresh gas flow is vaporizer output reduced

A

Flow <200 mL/min or > 15 L/min

99
Q

What complication can occur if the vaporizer is tipped over

A

The liquid anesthetic enters the bypass chamber and can increase vaporizer output. This can lead to anesthetic overdose

100
Q

How much anesthetic vapor does 1 mL of liquid anesthetic produce

A

~200 mL assuming STP

101
Q

What should you do if the vaporizer is tipped

A

Run high FGF for 20 - 30 minutes before use with a patient. This ensures the vapor is gone in the bypass chamber

102
Q

Why is temperature compensation necessary in vaporizers

A

Heat is carried away by vaporized molecules, causing the anesthetic liquid to cool. Cooling decreases vapor pressure and vaporizer output

103
Q

What is the purpose of the temperature compensating valve

A

Adjusting the ratio of vaporizing chamber flow to bypass flow to guarantee a constant vaporizer output over a wide range of temepratures

104
Q

What is the pumping effect and how is it minimized

A

Gas and vapor that has already left the vaporizer re-enters the chamber due to PPV or O2 flush valve. Low flow, low gas concentration and low levels of liquid augment the pumping effect

This is minimized by a backflow valve

105
Q

What are 2 causes of vaporizer leak

A
  1. Loose filler cap

2. Internal leak in vaporizer

106
Q

When is a vaporizer leak detected

A

It can only be detected when the vaporizer is turned on

107
Q

What is the equation to calculate how long the agent will last

A

mL of liquid anesthetic used per hour = Vol% x FGF(L/min) x 3

108
Q

How does the vaporizer for desflurane differ from the variable bypass vaporizer

A

There is no bypass flow for the des vaporizer

The des vaporizer injects a precise amount of desflurane directly into the FGF

109
Q

Why is the desflurane vaporizer heated

A

More volume is required to obtain same depth of anesthesia.
When more volume is carried away, excessive heat is lost causing the remaining liquid to cool and reducing vaporizer output

110
Q

What is the equation to calculate required dial setting for desflurane at elevation to obtain the desired percent delivery

A

Required dial setting = [Normal dial setting (% x 760 mmHg)] / ambient pressure mmHg

111
Q

What is the set temperature and pressure for a desflurane vaporizer

A 
Temp = 39*C
Pressure = 2 atm
112
Q

Where is the O2 analyzer

A

The inspiratory limb of the breathing circuit

113
Q

What is the purpose of the O2 analyzer (3)

A
  1. Monitor O2 concentration
  2. Detect an O2 pipeline crossover
  3. Detect hypoxic mixture caused by flowmeter leak
114
Q

Why will a pyrexic 70 kg patient become hypoxic with an O2 flow rate of 250 mL/min in a closed-circuit system

A

Because the flow rate is less than the pts O2 consumption

115
Q

What 2 steps must be performed when a pipeline crossover occurs

A
  1. Turn on O2 cylinder

2. Disconnect pipeline O2 supply

116
Q

If a pipeline crossover was assumed to be the reason for the O2 analyzer alarm but the O2 concentration in the breathing circuit isn’t increasing following pipeline disconnect, what should be done…

A

Assume a machine malfunction
Ventilate patient with ambu and O2 tank (do not use machine auxiliary O2 flowmeter which is supplied by pipeline)
Convert to TIVA

117
Q

What is the purpose of the O2 flush valve

A

Delivery of O2 from the intermediate-pressure system to the breathing circuit

118
Q

What is flow and pressure is the breathing circuit exposed to when pressing the O2 flush valve

A 
Flow = 35 - 75 L/min
Pressure = 50 psi
119
Q

How can the use of the O2 flush lead to patient awareness

A

It does not pass through the vaporizer

Excessive use can dilute the partial pressure of volatile agent and lead to awareness

120
Q

How does O2 flush use lead to barotrauma

A

Flushing during the inspiratory cycle can lead to barotrauma b/c the ventilator spill valve is closed during inspiration (won’t allow the excess pressure to be redirected)

121
Q

How does drive gas compress bellows

A
  1. the drive gas is outside the breathing circuit while the bellows is inside the circuit
  2. During inspiration, drive gas increases pressure inside vent chamber creating a pressure gradient the pushes the bellow and fresh gas into the patient
  3. On exhalation, the drive gas flow stop and the pressure gradient is reversed
122
Q

How does the spill valve function during inspiration

A

It is closed, ensuring Vt goes to the patient and not the scavenger

123
Q

How does the spill valve function during exhalation

A

The exhaled volume refills the bellows first. Once circuit pressure exceeds 3 cmH2O, the spill valve opens and excess gas exits the scavenger

124
Q

How do anesthesia machines minimize risk of barotrauma

A
  1. isolating Vt form flowmeter and O2 flush valve (decoupling)
  2. When circuit pressure is greater than a setpoint, the excess gas is vented out the scavenger (APL for ventilator)
125
Q

What 2 functions does the drive gas on a pneumatic ventilator serve

A
  1. Compresses the bellows

2. Opens and closes the ventilator spill valve

126
Q

How are bellows classified

A

By the movement during EXPIRATION
Ascending = RISE during expiration
Descending= FALLS during expiration

127
Q

What occurs when there is a circuit disconnect:
Ascending bellows=
Descending bellows=

A

Ascending bellows= bellows will not fill

Descending bellows= can continue to rise and fall

128
Q

What are complications of a leak in the bellows

A
  1. Exposure to high pressure gas to the breathing circuit
  2. Barotrauma
  3. Increasing FiO2 (if O2 is drive gas)
  4. Dilution of anesthetic vapor (risk for awareness)
129
Q

2 ways a piston ventilator differs from the bellows

A
  1. An electric motor compresses the piston that generates positive pressure in the breathing circuit
  2. Does no use drive gas
130
Q

What are the 2 pressure relief valves in the piston ventilator

A
  1. Positive pressure valve (guards against excess pressures in breathing circuit >75 cmH2O)
  2. The negative pressure valve guards against negative end-expiratory pressure <-8 cmH2O
131
Q

Is the piston vent coupled or decoupled from FGF

132
Q

With a piston ventilator, how does the breathing bag move on inspiration and expiration

A 
Inspiration = Inflates
Expiration = deflates
133
Q

Describe VCV

A

Delivery of a preset tidal volume over predetermined time

134
Q

How do inspiratory pressures respond to VCV

A

They vary as a function of a patients pulmonary compliance

135
Q

What causes increased PIP with VCV

A

Increased airway resistance

Decreased lung compliance

136
Q

Describe the inspiratory flow during VCV inspiration

A

It is held constant

137
Q

Describe PCV

A

Delivers a preset inspiratory pressure over a predetermined time

138
Q

How does Vt and inspiratory flow respond to PCV

A

they vary as a function of the patient’s pulmonary compliance

139
Q

What factors can decrease Vt with PCV

A

Increased airway resistance

Decreased lung compliance

140
Q

How does inspiratory flow function with PCV

A

It begins high to achieve the set inflation pressure then slows to maintain a constant inflation pressure

141
Q

What are the fixed parameters with VCV

A

Vt
Inspiratory flow rate
Inspiratory time

142
Q

What are the fixed parameters with PCV

A

Peak inspiratory pressure

Inspiratory time

143
Q

What are the variable parameters with VCV

A

Peak inspiratory pressure

144
Q

What are the variable parameters with PCV

A

Vt

Inspiratory flow

145
Q

What are 4 advantages of PCV

A
  1. Delivers larger Vt for given inspiratory pressure
  2. Inspiratory flow pattern may improve gas exchange
  3. Reduces the risk of ventilator-associated lung injury (VALI)
  4. Useful in patients with low compliance
146
Q

What are 2 disadvantages of PCV

A
  1. Increased airway resistance or decreased lung compliance reduce Vt
  2. Requires extra attention with conditions that alter pulmonary resistance or compliance (desufflation), causing large Vt changes
147
Q

What compliance factors decrease Vt with PCV

A
  1. Pneumoperitoneum

2. T-burg position

148
Q

What 2 resistance factors decrease Vt with PCV

A
  1. Bronchospasm

2. Kinked ETT

149
Q

What 2 compliance factors increase Vt with PCV

A
  1. Release of pneumoperitoneum

2. T-burg to supine

150
Q

What 2 resistance factors increase Vt with PCV

A
  1. Bronchodilator therapy

2. Removing airway secretions

151
Q

What are 3 categories when PCV would be better over VCV

A
  1. Patient has low compliance
  2. High PIP would be dangerous
  3. Need to compensate for a leak
152
Q

4 examples of patients with low compliance that would benefit from PCV

A
  1. Pregnancy
  2. Obesity
  3. Laparoscopy
  4. ARDS
153
Q

3 examples where PCV is preferred because high PIP would be dangerous

A
  1. LMA
  2. Neonate
  3. Emphysema
154
Q

2 examples where PCV is beneficial to compensate for a leak

A
  1. LMA

2. Uncuffed ETT in children

155
Q

Describe the setting of CMV and what patients are best suited

A

Mandatory Vt and RR
Does not compensate for patient initiated breaths

Best in apneic patients

156
Q

Risk associated with CMV

A

patient-ventilator asynchrony

157
Q

Describe the setting of assist control (AC)

A

Machine initiate breaths with set Vt and RR

Spontaneous breaths receive same set Vt

158
Q

What complications can be associated with AC ventilation

A

If patient over breaths they are at risk for hyperventilation and respiratory alkalosis

159
Q

Synchronized intermittent mandatory ventilation

A

Machine initiated breaths at set Vt and RR
Allows patient to breathe spontaneously
Adjusts timing of breaths if patient initiates

160
Q

How do patient initiated breaths appear of the vent screen

A

Negative deflection on waveform before inspiration

161
Q

Which vent mode promotes better synchrony between patient and vent

162
Q

Describe pressure-control ventilation with volume guarantee (PCV-VG)

A

Benefits of pressure control ventilation with a guaranteed predetermined Vt while applying minimum pressure to achieve the Vt

163
Q

Pressure-support ventilation (PSV)

A

Augments spontaneous breaths with pre-set amount of pressure support
No machine initiated breaths

164
Q

Which vent settings are useful for weaning or LMA

A

PSV
SIMV
PSV-Pro

165
Q

Describe continuous positive airway pressure (CPAP) setting

A
  1. Continuous amount of breath applied to breathing circuit thru respiratory cycle
166
Q

What are 2 benefits of CPAP

A
  1. the pressure augments the patient’s spontaneous breath

2. Pressure applied reduces airway collapse during expiration

167
Q

How do CPAP and PSV differ

A

PSV only applied pressure to the circuit when the patient initiates a breath

168
Q

Describe BiPAP

A

Two levels of pressure are set
P1 = inspiratory positive airway pressure (PSV)
P2 = expiratory positive airway pressure (CPAP)

169
Q

What is airway pressure release ventilation (APRV)

A

Similar to BiPAP but has a high level of CPAP throughout the respiratory cycle
Periodic release of high level of pressure to facilitate exhalation
Useful in ARDS and with spontaneous ventilation

170
Q

What is inverse ratio ventilation (IRV)

A

Reverse I:E ratio, allocating more time to inspiration and less to exhalation

171
Q

What is required to perform IRV

A

Paralysis and sedation

172
Q

In which patients is IRV useful

A

Patients with small FRC or ARDS

173
Q

What are the risks associated with IRV

A

dynamic hyperinflation (auto-peep or breath stacking)

174
Q

3 methods of gas transport with high-frequency ventilation

A
  1. molecular diffusion
  2. coaxial flow
  3. high-velocity flow
175
Q

What are 3 types of high-frequency ventilation

A
  1. high-frequency oscillation
  2. high-frequency jet ventilation
  3. high-frequency percussive ventilation
176
Q

How do CO2 absorbers remove exhaled CO2 from the breathing circuit

A

A strong base (NaOH) neutralizes CO2 through a chain of reactions involving H2O and Ca(OH)2

177
Q

What is the first step in CO2 neutralization via soda lime

A

Co2 + H2O => H2CO3 (carbonic acid)

178
Q

What is the second step in CO2 neutralization via soda lime

A

H2CO3 + 2NaOH => Na2CO3 + H2O + heat

179
Q

What is the third step in CO2 neutralization via soda lime

A

Na2CO3 + Ca(OH)2 => CaCO3 + 2NaOH

180
Q

How does the size of the soda lime granule affect absorption and work of breathing

A

Absorption = more surface area with smaller granules

Work of breathing = increased with small granules, decreased with large

181
Q

What is the ideal size of soda lime granules to balance absorptive capacity and work of breathing

A

4 - 8 mesh granules

between 1/8 to 1/4 inch in diameter

182
Q

What 2 problems with soda lime can lead to complications

A
  1. Exhaustion

2. Desiccation

183
Q

What happens to the pH of soda lime as it neutralizes CO2

184
Q

At what pH does the indicator dye signal soda lime exhaustion

185
Q

What action should be taken if FiCO2 increases and the absorbent can’t be changed

A

Increase FGF
Make circle system semi-open
Prevent rebreathing

186
Q

How can you tell when a CO2 absorber is dessicated

A

You can’t

There is not indicator

187
Q

What are the risks of desiccated soda lime

A

Production of CO

188
Q

Which anesthetics produce more CO in the presence of a desiccated soda lime

A

des > iso&raquo_space;> sevo

189
Q

What does sevoflurane produce in the presence of a desiccated absorber

A

Compound A

190
Q

Which anesthetic is the most unstable in the presence of soda lime

191
Q

What are 5 methods to minimize the risk of CO and compound A in desiccated soda lime

A
  1. Utilize low FGF to preserve H2O
  2. Turn of FGF between cases
  3. Change absorbent at one time
  4. change canister when indicator is violet
  5. Change if unsure about level of hydration (was FGF left on overnight?)
192
Q

How are the irritating effects of NaOH in CO2 absorber addressed

A

Silica is added to provide hardness and minimize dust production

This decreases chance for bronchial irritation or bronchospasm

193
Q

how does the calcium hydroxide lime differ from soda lime

A
  1. Doesn’t contain strong bases
194
Q

What are 3 benefits of calcium hydroxide lime over soda lime

A
  1. No CO production
  2. Very little or no compound A production
  3. Less fire risk
195
Q

What are 2 disadvantages of the calcium hydroxide lime vs soda lime

A
  1. Absorbs less CO2

2. More expensive

196
Q

What is the first step of calcium hydroxide lime CO2 neutralization

A

CO2 + H2O => H2CO3

197
Q

What is the second step of calcium hydroxide lime CO2 neutralization

A

H2CO3 + 2Ca(OH)2 => CaCO3 + 2H2O + Heat

198
Q

What are 2 purposes of the scavenging system

A
  1. Removes excess gas from the breathing circuit

2. Minimizes environmental exposure to anesthetic gas waste

199
Q

What are the 5 components of the scavenger system

A
  1. Gas collection assembly
  2. Transfer tubing
  3. Interface (open or closed)
  4. Gas disposal tubing
  5. Gas disposal system
200
Q

During spontaneous ventilation, what controls the amount of gas released to the scavenger vs in the circuit

A

The APL valve

201
Q

During mechanical ventilation, what controls the amount of gas in the circuit and what is released to the scavenger

A

The spill valve

202
Q

What are the 2 types of scavenging systems. Describe the difference

A

Active = suction used to remove waste gas

Passive = relies of positive pressure of FGF to push gases

203
Q

How is negative pressure generated with the scavenging system

A

Removal of too much gas creates negative pressure in the circuit

204
Q

How can a scavenging system contribute to barotrauma

A

If not enough gas is being removed, there is a risk for barotrauma

205
Q

How is gas flow to the scavenging system controlled in the following situations
Spontaneous ventilation
Mechanical ventilation

A

Spontaneous ventilation = APL valve

Mechanical ventilation = spill valve

206
Q

How does an open scavenging system function

A
  1. Open to atm
  2. Only used with active systems (suction)
  3. No need for +/- pressure relief valves
  4. The amount of suction determines if waste gas is exhausted to the OR
    - Too little suction means the waste gas exits the system to the OR
207
Q

What are 3 benefits of an open scavenging system interface

A
  1. No need for +/- pressure relief valves
  2. Removes risk of barotrauma
  3. Decreases risk of negative pressure on circuit
208
Q

What are 3 disadvantages of the open scavenging system interface

A
  1. Can only be used with suction
  2. Increases possibility of exposure of OR staff to waste gas
  3. The amount of suction determines if waste gas goes to the OR vs entraining air into system
209
Q

Describe how the closed scavenging system functions

A

It communicates with atm via positive and negative pressure valves.
It is a passive system relying on positive pressure for forward flow

210
Q

What are the disadvantages of the closed scavenging system interface

A
  1. Requires pressure relief valves to atm

2. Excess FGF is not removed from breathing circuit, increasing risk for barotrauma

211
Q

Most common cause of low pressure alarm

A

Circuit disconnect

212
Q

What are 5 causes of low pressure in the breathing cicircuit

A
  1. CO2 absorbent canister leak (poor seal or defective canister)
  2. Malfunction of bag/vent selector switch
  3. Incompetent ventilator spill valve
  4. Leaks in breathing circuit
  5. Leaks in anesthesia machine
213
Q

What is the second most common cause of circuit leak

A

CO2 absorbent canister problems

  1. Poor seal
  2. Defective canister
214
Q

Does the O2 analyzer alert when there is a disconnection?

A

No, it only reads the O2 concentration in the circuit

215
Q

What should you do if the circuit doesn’t hold pressure

A

Ventilate pt with BVM and O2 tank and convert to TIVA

216
Q

What are 4 ways to detect a circuit disconnect

A
  1. Pressure
  2. Volume
  3. EtCO2
  4. Vigilance
217
Q

What are 9 complications of excessive pressure in the breathing circuit

A
  1. Barotrauma
  2. Decreased venous return
  3. Decreased CO
  4. HoTN
  5. CV collapse
  6. High PEEP
  7. PTX
  8. SQ emphysema
  9. Death
218
Q

What are 6 causes of high pressure inside the breathing circuit

A
  1. Vent spill valve malfunction
  2. CO2 absorbent obstruction
  3. Anesthesia mask obstruction
  4. Occluded limb of breathing circuit
  5. Malfunctioning PEEP valve
  6. Malfunctioning expiratory unidirectional valve
219
Q

When a high pressure alarm sounds, what is the first thing that should be assessed

A

THE PATIENT

-Ensure pt isn’t having bronchospasm

220
Q

What are 11 CRNA related methods to decrease staff exposure to anesthetic gases

A
  1. Ensure good mask fit
  2. Tun on gas when mask fit is good
  3. Prevent FGF from entering atm
  4. Turn off gas before suctioning patient
  5. Evacuate anesthetic gases into scavenger at the end of case
  6. Use cuffed ETT
  7. Vigilance for anesthesia machine leaks
  8. Don’t spill agents
  9. Use TIVA
  10. Avoid N2O
  11. Low FGF
221
Q

What are 2 environmental factors that decrease exposure to waste gas

A
  1. OR ventilation and air turnover

2. Functional anesthesia equipment

222
Q

What is the maximum OSHA recommended exposure to inhaled anesthetics
Halogenated agents=
N2O alone=
Halogenated agents + N2O=

A

Halogenated agents= <2 ppm

N2O alone= <25 ppm

Halogenated agents + N2O= <0.5 ppm, <25 ppm respectively

APEX-Equipment (7 decks)

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