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N928 - Basic Principles > Ventilation Modes & Oxygen Therapy > Flashcards

Ventilation Modes & Oxygen Therapy Flashcards

1
Q

What are the 3 controlled mechanical ventilation modes/

A
  1. Volume Controlled Ventilation (VCV)
  2. Pressure Controlled Ventilation (PCV)
  3. Pressure Controlled-Volume Guaranteed Ventilation (PCV-VG)
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2
Q

What are 2 other methods of ventilation in addition to controlled ventilation modes?

A
  1. synchronized intermittent mandatory ventilation (SIMV)

2. Pressure Support Ventilation (PSV)

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3
Q

Looking at the flow tracing, how do you know what mode the ventilator is set at?

A

Volume control will have “square” shape

Pressure control will have decelerating flow shape

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4
Q

What is the resistive pressure?

A

overall pressure required to distend the lungs and airways

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5
Q

What is the distending pressure?

A

pressure needed to open lungs to provide O2 delivery and CO2 removal

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6
Q

What is the Peak Inspiratory Pressure tell providers about?

A

both intrinsic & extrinsic (chest wall & muscle) compliancec

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7
Q

What does the Plateau Pressure (pplat) tell us about?

A

the intrinsic compliance of the lung

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8
Q

What is the total pressure required to distend the lungs & airways?

A

the peak inspiratory pressure

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9
Q

What is the distending pressure required to expand the lungs?

A

Plateau Pressure

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10
Q

What pressure is used to calculate dynamic compliance?

A

Peak inspiratory pressure

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11
Q

What pressure is used to calculate static compliance?

A

Plateau Pressure (pplat)

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12
Q

How is a plateau pressure obtained?

A

must be in volume control with an inspiratory hold

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13
Q

What compliance does dynamic compliance tell you about?

A

total respiratory compliance

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14
Q

What compliance does static compliance tell you about?

A

intrinsic/lungs themselves compliance

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15
Q

During a plateau pressure, what does the drop in pressure indicate?

A

redistribution of gas flow throughout the lungs

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16
Q

What are the 4 variables that can be controlled during mechanical ventilation?

A
  1. respiratory rate
  2. tidal volume
  3. pressure (PiP / Pplat / PAW
  4. I:E ratio
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17
Q

What can happen if you increase only the RR in a pressure mode?

A

decreased tidal volume = decreased minute ventilation d/t shortening of insp / exp time

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18
Q

Each breath has 4 parts which are?

A
  1. start of inspiration
  2. inspiration itself
  3. end of inspiration
  4. expiration
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19
Q

What is the trigger variable? and what are the 4 types?

A

represents the start of inspiration

  1. pressure
  2. volume
  3. flow
  4. time
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20
Q

What is the limit variable?

A

maintenance of inspiration

aka: target variable

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21
Q

What is the target variable?

A

maintenance of inspiration

aka limit variable

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22
Q

What is the cycling variable?

A

transition of expiration

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23
Q

What is the baseline variable?

A

end of expiration

aka PEEP

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24
Q

The pressure trigger variable:

A

decrease in circuit pressure stimulates ventilator to deliver a breath

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25
Q

The volume trigger variable:

A

volume change in the circuit can stimulate the ventilator to deliver a breath

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26
Q

The flow trigger variable:

A

change of the flow in the circuit stimulates the ventilator to deliver a breath

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27
Q

The time trigger variable:

A

a set time interval triggers the ventilator to deliver a breath

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28
Q

What variable are we most concerned about?

A

the TRIGGER variable

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29
Q

What does the limit variable control?

A

how the inspiratory breath is maintained.

once the threshold is reached, the variable will not exceed a set limit

**does not cause termination of inspiration

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30
Q

Limit variable set as pressure sets what?

A

the upper pressure limit that cannot be exceeded

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31
Q

What can initiate the pressure trigger?

A

patient
or
an outside source (ie. surgeon pulling/pushing on patient)

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32
Q

What is tidal volume commonly set to?

A

8-12mL/kg

can be as low as 6mL/kg
[prevent overdistention and injury]

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33
Q

What is the respiratory rate commonly set to?

A

10-20 bpm

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34
Q

What is minute ventilation? (VE)

A

the average volume of gas entering or leaving the lungs per minute.

Usually L/min

Vt x RR = VE

normal 5-10L/min

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35
Q

What is normal VE?

A

5-10L/min

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36
Q

What is peak flow rate?
aka
peak inspiratory flow

A

highest flow, or speed, that is set to deliver the Vt during inspiration, usually L/min

the higher the flow rate, the faster the air is delivered and SLOWER the inspiratory time is

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37
Q

What is inspiratory:expiratory time?

I:E ratio?

A

speed at which the Vt is delivered. Setting a shorter inspiratory time results in faster inspiratory flow

average adult inspiratory time 0.7 - 1

I:E ratio is usually 1:2 or 1:3

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38
Q

What is a normal I:E ratio?

A

1:2 or 1:3

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39
Q

What is the peak airway pressure?

Paw

A

represents the total pressure that is required to deliver the Vt and depends upon various airway resistance, lung compliance, and chest wall factors.

expressed in cmH2O

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40
Q

What is the plateau pressure?

A

pressure that is needed to distend the lunch, which an be measured by applying an end-expiratory pause setting on the ventilator.
expressed in cmH2O

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41
Q

What is the sensitity or trigger sensitivity?

A

negative pressure [effort] required to trigger a machine breath, commonly set to -1 or -2 cm H2O [minimal] effort is needed.

some vents have flow triggering which is more sensitive.

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42
Q

What is PEEP?

A

the amount of positive pressure that is maintained at end-expiration.

cmH2O

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43
Q

What is the purpose of PEEP?

A

to increase end-expiratory lung volume and reduce air-space closure at end expiration

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44
Q

What is CPAP?

A

continuous pressurization of the breathing circuit when a patient breathes spontaneously. CPAP may be used as a last step in the weaning process or as a non-invasive method of providing a pneumatic splint to the upper airway in obstructive sleep apnea

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45
Q

What is a mandatory breath?

A

breath in which the timing and/or size of the breath is controlled by the ventilator; the machine triggers and/or cycles the breath

46
Q

What is a spontaneous breath?

A

breath in which both the timing and size are controlled by the patient; the patient both triggers and cycles the breath

47
Q

What are 4 volume-targeted ventilator modes

A

CMV
VCV
A/C
SIMV

48
Q

What are 2 pressure-targeted ventilator modes?

A

PSV

PCV

49
Q

When does inspiration terminate in a volume targeted ventilator mode?

A

when a preset Vt has been delivered

50
Q

When does inspiration terminate in a pressure targeted ventilator mode?

A

when a preset pressure is reached.

preset pressure delivered; volume is variable and determined by set pressure level, airway resistance, and lung compliance factors, specified time or flow cycling criteria

51
Q

In a pressure targeted mode, is the inspiratory flow rate fixed or variable?

A

variable.

52
Q

What happens if a patient inspires faster or more vigorously when on a pressure targeted mode?

A

the flow rate may need to be changed

53
Q

Is the inspiratory flow rate fixed or variable in a volume targeted mode?

A

fixed.

54
Q

What happens if a patient inspires faster or more vigorously when on a volume targeted mode?

A

WOB will increase, flow rate or other settings need to be changed

55
Q

What is the abbreviation for oxygen delivery?

A

DO2

56
Q

What is the oxygen delivery equation?

A

DO2 = CO x arterial O2 content

57
Q

What is one value (from a blood gas) that can indicate an O2 delivery issue?

A

the base deficit

58
Q

What is VO2?

A

oxygen use

59
Q

What is the equation for VO2?

A

CO x O2a - O2v

60
Q

What is a normal oxygen extraction ratio?

A

25%

61
Q

What is special about oxygen extraction of the heart?

A

the heart has a very high oxygen demand

62
Q

What is hypoxemia?

A

deficiency of O2 in the blood

63
Q

What is hypoxia?

A

O2 delivery to the tissues is not adequate to meet metabolic demand

64
Q

What is anesthesia’s goal in oxygen therapy?

A

maintain oxygenation and ventilation

65
Q

What is the goal of oxygen therapy?

A

prevention and correction of hypoxemia and tissue hypoxia

66
Q

What are the 5 types of hypoxia?

A
  1. hypoxic
  2. circulatory
  3. Hemic
  4. Demand
  5. Histotoxic
67
Q

What is hypoxic hypoxia?

A

shunt of pulmonary diffusion defect;

  • drug overdose causing hypoventilation
  • COPD
    asthma
    emphysema
  • atlectasis
68
Q

What is circulatory hypoxia?

A

↓ CO d/t MI, congestive HF

69
Q

What is hemic hypoxia?

A

↓Hgb or fxn of Hgb

70
Q

What is demand hypoxia?

A

↑O2 consumption (fever, Sz, MH)

71
Q

What is histotoxic hypoxia?

A

inability of cells to USE oxygen (cyanide toxicity)

72
Q

What are 6 s/s of hypoxia?

A
  1. vasodilation
  2. tachycardia
  3. tachypnea
  4. cyanosis
  5. confusion
  6. lactic acidosis
73
Q

What is the treatment of hypoxia in mechanically ventilated patients?

A

tailored to treat the cause

74
Q

What are 6 possible methods of increasing oxygenation in a ventilated patient?

A

1 . increase VE (minute ventilation)

  1. Increase CO
  2. Increase O2 carrying capacity
  3. Optimize V/O relationship (↓PEEP)
  4. Decrease O2 consumption
  5. increase FiO2
75
Q

What are 4 methods of oxygen delivery in non-ventilated patients

A
  1. nasal cannula
  2. simple face mask
  3. face mask with reservoir
  4. venturi mask
76
Q

What is the flow rate/ % O2 delivery of a nasal cannula?

A

1-6L/min

4% per L

77
Q

What is the flow rate/ % O2 delivery of a simple face mask?

A

minimum flow of 6L to prevent rebreathing

40-60%

→ must provide at least the minute ventilation in flow to prevent rebreathing

78
Q

What is the FiO2 delivery of a face mask with a reservoir?

A

60-100%

79
Q

What is the FiO2 delivery of a venturi mask?

A

24-50% (more precise)

check set up for correct flow rate

80
Q

What principle does a venturi face mask use?

A

Bernoulli principle

81
Q

What are 3 sequalae of high FiO2 on lung tissue?

A
  1. decreased ciliary movement = lungs can’t mobilize mucous
  2. alveolar epithelial damage
  3. interstitial fibrosis
82
Q

Damage to lung tissue from high FiO2 is dependent upon what 3 factors?

A
  1. FiO2
  2. duration of therapy
  3. patient susceptibility
83
Q

Delivery of 100% FiO2 is safe for how long?

A

10-20 hours

84
Q

Delivery of 50-60% FiO2 is safe for how long?

A

24-72 hours

85
Q

Toxicity of 50-60% FiO2 is seen after how long?

A

24-72 hours

86
Q

What is absorption atelctasis?

A

nitrogen is replaced in the lung by oxygen.

alveoli become UNDER VENTILATED and have DECREASED VOLUME

increase pulmonary shunting (perfusion w/o ventilation)

WIDENING OF THE A-a gradient

87
Q

At what FiO2 is absorption atelectasis likely to not occur?

A

60% FiO2

88
Q

What is induced hypoventilation?

A

chronic CO2 retainers become hypercapnic
→ rely on hypoxemia for respiratory drive. (peripheral chemoreceptors are triggered by hypoxemia)
→ high amounts of delivered O2 can cause apnea

(theory)

89
Q

What patients are at highest risk for oxygen toxicity? (3 patient populations)

A
  1. elderly >70y
  2. Hx radiation to the chest
  3. Bleomycin [methotrexate]
90
Q

What are 6 s/s of oxygen toxicity?

A
  1. cough
  2. rales
  3. dyspnea
  4. hypoxemia
  5. ↑ A-a gradient
  6. ↓ diffusion capacity
91
Q

When are providers MOST concerned about intra-operative fire?

A

head and neck cases with high FiO2

** tracheostomy patients. already have induced atelectasis (likely) from long term mechanical ventilation and O2 requirement.

find balance communicating with surgeon about oxygenating… cautery… oxygenating… cautery

92
Q

What should be considered when using cautery or lasers on the head or neck?

A
  • use LOW FiO2.
  • O2 can build up under drapes
  • COMMUNICATE with the surgeon if FiO2 is needed
  • it is possible to connect nasal cannula to common gas outlet and deliver <100% FiO2
93
Q

What is retinopathy?

A

exponential growth of the retinal vasculature [scarring]

  • vascular proliferation, fibrosis, retinal detachment, blindness
94
Q

What 3 characteristics of patients are most at risk for retinopathy?

A
  1. < 36 weeks gestation
  2. weight < 1500g
  3. up to 44 weeks gestation = high risk
95
Q

What is considered “safe” O2 delivery for patients that are at high risk of developing retinopathy?

A

PaO2 60-80 mmHg

96
Q

What is hypercapnia?

What are the causes?

A

CO2 > 45mmHg

  1. increased CO2 concentration (lack of removal)
  2. increased CO2 production
97
Q

What are 2 causes of hypercapnia in relation to V/Q mismatch?

A
  1. increased alveolar dead space

2. decreased alveolar ventilation

98
Q

How does increased alveolar dead space lead to hypercapnia?

A

decreased alveolar perfusion
interruptions in pulmonary circulation
pulmonary disease

99
Q

What are the 2 types of defects that can cause decreased alveolar ventilation, leading to hypercapnia?

A

can be central or peripheral defect

** respiratory depression is the most common cause of hypercapnia in the postoperative period

100
Q

What are 6 non-specific signs of hypercapnia?

A

headache, nausea/vomiting, sweating, flushing, shivering, restlessness

101
Q

What are 3 manifestations of hypercapnia (not signs)?

A
  1. vasodilation of peripheral vessels (direct)
  2. increased HR from catecholamine release (indirect)
  3. effects d/t an acidotic state
102
Q

What are CNS considerations of hypercapnia?

A
  1. regulation of ventilatory drive
  2. cerebral blood flow (dilation of vessels)

↑CO2 = ↑RR

1mmHg increase in PaCO2 will increase cerebral blood flow by 1-2mL/100g/min

103
Q

1mmHg increase in CO2 will increase cerebral blood flow by how much?

A

1-2mL/100g/min

104
Q

What are cardiovascular considerations of hypercapnia?

A
  1. depression of smooth muscle
  2. depression of cardiac muscle
  3. increased catecholamine release
  4. vasodilation vs vasoconstriction
    - VD initially then ↑SNS results in VC
105
Q

What are pulmonary considerations of hypercapnia?

A
  1. increased RR
  2. increased pulmonary vascular resistance

*60% increase in pulmonary artery pressures

106
Q

Hypercapnia will shift the oxyhemoglobin dissociation curve which way?

A

to the right

107
Q

How is hypercapnia treated?

A

1 treat cause

  • increase minute ventilation

bad CO2 scrubber?

108
Q

What is hypocapnia?

A

PaCO2 < 35mmHg

109
Q

What is the most common cause of hypocapnia?

A

iatrogenic

110
Q

What are the CNS manifestations of hypocapnia?

A

decreased CBF

[can be beneficial with ↑ ICP or neurosurgery]

111
Q

What are the cardiovascular manifestations of hypocapnia?

A

decrease in CO, coronary artery constriction

alkalosis can lead to ↓iCa

112
Q

What are the pulmonary manifestations of hypocapnia?

A

hypoxemia may result from hypoventilation

N928 - Basic Principles (22 decks)

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