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Principles Of Anesthesia I > Breathing Systems I (Exam II) > Flashcards

Breathing Systems I (Exam II) Flashcards

1
Q

Define a breathing system

A
  • Receives gas mixture from the machine
  • Delivers gas to the patient
  • Removes CO2
  • Provides heating and humidification of the gas mixture
  • Allows spontaneous, assisted, or controlled respiration
  • Provides gas sampling, measures airway pressure, and monitors volume
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2
Q

When gas passes through a tube, the pressure at the _ will be lower than at the _.

A

Outlet
Inlet

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3
Q

The drop in pressure is a measure of the _ that must be overcome.

A

Resistance

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4
Q

Resistance varies with the _ of gas passing through per unit of time.

A

Volume
(Higher volume = more pressure)

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5
Q

_ type can change with resistance.

A

Flow

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6
Q

What are the two types of flow?

A
  • Laminar
  • Turbulent
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7
Q

Describe Laminar Flow

A
  • Flow is smooth and orderly
  • Particles move parallel to the tube walls
  • Flow is fastest in the center where there is less friction
    (Related to Poiseulle’s Law)
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8
Q

Describe the following types of flow.

A

A. Laminar Flow
B. Generalized Turbulent Flow
C. Laminer Flow into Turbulent Flow with diameter change
D, E, F : Changes in angles leading to Turbulent Flow

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9
Q

Describe Turbulent Flow

A
  • Flows are not parallel
  • Flow rate is same across diameter of tube
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10
Q

What are “Eddies”?

A

Particles moving across or opposite the general direction of flow.
(In relation to Turbulent Flow)

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11
Q

What are the two types of Turbulent Flow?

A
  • Generalized
  • Localized
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12
Q

Describe Generalized Turbulent Flow

A

When the flow of gas through a tube exceeds the critical flow rate

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13
Q

Describe Localized Turbulent Flow

A

Gas flow rate is below the critical flow rate, but encounters constrictions, curves, or valves

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14
Q

What is Critical Flow Rate?

A

Rate that must be reached to achieve Turbulent Flow

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15
Q

What causes more resistance the ETT or the breathing system itself?

A

The ETT

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16
Q

Looking at Flow-Volume loops can _.

A

Show you the type or amount of resistance present for that particular patient

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17
Q

What is compliance?

A

Ratio of the change in volume to change in pressure
(Measures distensibility in mL/cm H2O)
(Helps determine tidal volume)

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18
Q

What are the most distensible components of the breathing system?

A
  • Breathing tubes
  • Reservoir bags
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19
Q

Define rebreathing

A

To inhale previously inspired gases from which CO2 may or may not have been removed
(inspired gas composition is part fresh gas and rebreathed gas)

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20
Q

Rebreathing is influenced by what 3 factors?

A
  • Fresh gas flow
  • Dead space
  • Breathing system design
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21
Q

What is the relationship between Fresh Gas Flow (FGF) and rebreathing?

A

Rebreathing varies inversely with the total FGF

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22
Q

If the volume of FGF supplied per min is _ or _ than the pt minute volume, _ .

A

Equal
Greater
No rebreathing occurs
(As long as exhaled gas is vented)

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23
Q

If the volume of FGF supplied per min is _ the pt minute volume, _ .

A

Less than
Rebreathing occurs
(Some of the exhaled gases must be rebreathed to make up required volume)

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24
Q

What is apparatus dead space?

A

Volume in a breathing system occupied by gases that are rebreathed without change in composition

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25
Q

How can apparatus dead space be decreased?

A

By having the inspiratory and expiratory limb separation as close to the patient as possible

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26
Q

What is physiologic dead space?

A

Anatomical + Alveolar dead space

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27
Q

What is anatomical dead space?

A

Conducting airways; adds H2O vapor

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28
Q

What is alveolar dead space?

A

Volume of alveoli ventilated but not perfused

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29
Q

Describe no rebreathing

A

Inspired gas composition is identical to the fresh gas delivered by the anesthesia machine

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30
Q

What is a benefit of rebreathing?

A

Reduces heat and moisture loss from the pt
(Way of humidification)

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31
Q

What are some effects of rebreathing?

A

Altering inspired gas tensions or partial pressures:
* Oxygen
* Anesthetic agents
* Carbon Dioxide

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32
Q

What are the 6 desirable characteristics of a Breathing Circuit?

A
  1. Low resistance to gas flow
  2. Minimal rebreathing
  3. Removal of CO2 at rate of production
  4. Rapid changes in delivered gas when required
  5. Warmed humidification of inspired gas
  6. Safe disposal of waste gases
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33
Q

This type of circuit is characterized by no reservoir bag and no rebreathing.

A

Open Circuit

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34
Q

This type of circuit is defined by a reservoir bag and complete rebreathing. This circuit is also dependent on fresh gas flow.

A

Closed Circuit

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35
Q

This type of circuit is characterized by a reservoir bag with no rebreathing.

A

Semi-open Circuit

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36
Q

This type of circuit is characterized by a reservoir bag and partial rebreathing.

A

Semi-closed Circuit

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37
Q

What are components of a breathing circuit?

A
  • A facemask, LMA, or ETT
  • A Y-piece with mask/tube connectors
  • Breathing tubing
  • Respiratory valves
  • Reservoir bag
  • A fresh gas inflow site
  • A pop-off valve leading to scavenging
  • Carbon dioxide absorption canister
38
Q

Where is a mask supposed to fit on a patient’s face?

A

In between the interpupillary line and the groove between the mental process and alveolar ridge.

39
Q

What size is the connection that fits the mask to the Y-piece of the machine.

A

22mm female connector

40
Q

What are the general benefits of connectors/adapters on the airway portion of the anesthesia machine?

A
  • extends distance between patient and breathing system
  • change angle of connection
  • allow flexibility
41
Q

What are the general disadvantages of connectors/adapters on the airway portion of the anesthesia machine?

A
  • increased resistance
  • increased dead space
  • additional points of failure/disconnection
42
Q

How long is breathing tubing?
How much internal volume does it typically have?

A
  • 1 meter long
  • 400-500 mL/m of length
43
Q

What type of flow is typically present in corrugated breathing tubing?

A

Turbulent due to corrugation

44
Q

Does adding longer tubing increase dead space?

A

No it does not
Only adds dead space if bidirectional air flow is occurring.

45
Q

What adds dead space?

A

Y-piece attached to patient due to unidirectional gas flow

46
Q

At what pressure should a circuit pressure check be done?

A

30 cmH₂O

47
Q

What is required for dead space?

A

Bidirectional gas flow
Includes anatomic dead space, ETT, and Y-piece.

48
Q

A unidirectional valve is broken. Is the attached inspiratory limb considered dead space?

A

Yes, now bidirectional gas flow is occurring. If valve is fixed then the limb will not be considered dead space again.

49
Q

Which valve opens on exhalation & prevents rebreathing?

A

Expiratory valve

50
Q

Which valve opens on inhalation & prevents backflow of exhaled gas?

A

Inspiratory valve

51
Q

What are the 5 requirements for unidirectional valves?

A
  1. Arrows or directional words
  2. Hydrophobic
  3. Must open and close appropriately
  4. Clear dome
  5. Must be placed between pt and reservoir bag
52
Q

What shape do breathing/reservoir bags have?

A

Ellipsoidal
(To make it easier for 1-hand ventilation)

53
Q

What volume do breathing bags have?

A

3L for adults

(0.5 - 6L range)

54
Q

What is the minimum pressure of a breathing bag?

A

30 cmH₂O

55
Q

What is the max pressure of breathing bags?

A

40 - 60 cmH₂O

56
Q

Plastic bags have ____ the distending pressure of rubber bags.

A

2x

57
Q

What functions does the breathing/reservoir bag serve?

A
  • Reservoir for gases & O₂
  • Manual ventilation
  • Assistance w/ spontaneous ventilation
  • Protection from excessive positive pressure
  • Visual/tactile monitoring of ventilation
58
Q

Where is the preferred location for the fresh gas inlet?

A

Between the CO₂ absorbent and inspiratory valve

59
Q

What is the purpose of the APL (adjustable pressure limiting) Valve?

A
  • Permits gas to leave the circuit to the scavenging system
  • Controls pressure in the breathing system
60
Q

Turning the APL valve in a clockwise motion will ____ pressure.

A

increase

61
Q

Turning the APL valve in a counterclockwise motion will ____ pressure.

A

decrease

62
Q

How many turns are required to go from fully open to fully closed on the APL valve?

A

1-2 clockwise turns

63
Q

When replacing a CO2 absorber, you should _.

A

Remove the plastic wrap

64
Q

What is the purpose of the side/center tube located in the absorbent cannister?

A

Returns gas to the patient

65
Q

What is the chemical formula for soda lime?

A

Ca(OH)₂

66
Q

What is the chemical reaction that occurs with soda lime in a CO₂ absorbent cannister?

A

CO₂ + Ca(OH)₂ → CaCO₃ + H₂O + heat
(Just be aware absorbant is a chemical rxn)

67
Q

What are the components of soda lime?

A
  • Calcium hydroxide (80%)
  • Sodium & potassium hydroxide (5%)
  • Water (15%)
  • Small amounts of silica and clay
68
Q

When does soda lime become exhausted?

A

When all hydroxides become carbonates

69
Q

How much CO₂ can soda lime absorb?

A

19% of its weight
100g can absorb 26L of CO₂

70
Q

What are the problems with strong absorbers containing sodium hydroxide or potassium hydroxide?

A

Can lead to the formation of Compound A, CO, or destruction of inhaled gases

71
Q

What absorbent has greater absorption capacity and is used in submarines and spacecraft?

A

Lithium Hydroxide

72
Q

Which absorbent is responsible for compound A & CO formation?

A

Calcium Hydroxide Lime

73
Q

What is the chemical name of Litholyme?

A

Lithium chloride

74
Q

What are the benefits of Litholyme (Lithium chloride) ?

A
  • No compound A formation
  • No reaction with inhaled anesthetic agents
  • pH indicators do not become colorless (no regeneration)
  • Low exothermic reactivity, and low risk of fire, better for environment
75
Q

What absorbent has no color indicator?

A

Spira-Lith (Anhydrous LiOH)

76
Q

What are the benefits of Spira-Lith?

A
  • Large reaction surface area (non-granular, polymer sheets)
  • ↓ temperature production
  • Long duration
  • Cheap
77
Q

What does your capnography look like when your CO2 absorber is exhausted?

A

Baseline rises

78
Q

What dyes are used in CO₂ absorbents?

A
  • Ethyl Violet (most common)
  • Ethyl orange (orange to yellow)
  • Cresyl yellow (yellow to red)
79
Q

At what pH do absorbents undergo color change?

A

10.3
pH > 10.3 (absorbent is colorless & fresh)
pH < 10.3 (exhausted & purple absorbent)

80
Q

What is the purpose of the mesh located in CO₂ absorbents?

A

Maximize absorption and minimize resistance

81
Q

What will excess liquid water do inside a CO₂ absorbent cannister?

A

↓ surface area
↓ absorbent efficiency

82
Q

Approximately how much of a CO₂ absorbent cannister’s volume is gas?

A

½

83
Q

What is channeling and its consequence?

A
  • Small passage ways allowing gas to flow through a defined route
  • Decreases functional absorptive capacity

E is channeling

84
Q

How can channeling be minimized?

A
  • Circular baffles
  • Placement for vertical flow
  • Permanent mounting
  • Prepackaged cylinders
  • Avoiding over packing
85
Q

How does compound A form?

A
  • Low FGF
  • Increased absorbent temperature
  • Higher inspired Sevo concentrations
  • Dehydrated absorbent
86
Q

Which gases produce the most CO?
The least?

A

Desflurane ≥ Enflurane > Isoflurane > Halothane > Sevo
Sevo

87
Q

Desflurane in the presence of a dried-out absorbent in the presence of a strong hydroxide would lead to the formation of _.

A

CO

88
Q

What other factors cause CO to form?

A
  • Increased temperatures
  • Increased concentrations of anesthetic gases
  • Low FGF rates
  • Strong base absorbents
89
Q

Why should sevoflurane use with dessicated strong base absorbents (baralyme, LiOH) be avoided?

A

High risk of fire

90
Q

What are the APSF recommendations?

A
  • ALL gas flows turned off after each case
    (Vaporizers turned off when not in use)
  • Absorbent changed regularly
  • Change when color change indicates exhaustion
  • Change all absorbent
    (2 canister system – change both, not 1)
  • Change absorbent when uncertain about the state of hydration
  • If using compact canisters, change more frequently

Principles Of Anesthesia I (8 decks)

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