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APEX > Unit 6 - Respiratory Monitors & Equipment > Flashcards

Unit 6 - Respiratory Monitors & Equipment Flashcards

1
Q

formula for dynamic compliance

A

Vt / PIP - PEEP

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2
Q

which phase of the capnograph waveform best correlates to V/Q status

A

phase III

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3
Q

what point of capnograph is EtCO2 measured

A

point D

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4
Q

what gases can infrared analysis measure

A
  • N2O
  • CO2
  • volatiles

NOT O2, helium, Nitrogen, or xenon

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4
Q

what gases can infrared analysis measure

A
  • N2O
  • CO2
  • volatiles

NOT O2

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5
Q

handwritten notes - paco2 to etco2 gradient

A
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6
Q

what is the Beer Lambert law

A

relates the intensity of light transmitted through a solution & the concentration of the solute within solution

basis of pulse ox

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7
Q

Airway Resistance =

A

[P (airway) – P (alveolar)] / Gas Flow Rate

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8
Q

Airway Compliance =

A

change in volume / change in pressure

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9
Q

factors that influence airway compliance

A
  • muscle tone
  • degree of lung inflation
  • alveolar surface tension
  • amount of interstitial lung water
  • pulmonary fibrosis
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10
Q

Dynamic Compliance

A

compliance of lung/chest wall during air movement

Pressure required to inflate lung to a given volume is a function of air

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11
Q

Dynamic Compliance

A

compliance of lung/chest wall during air movement

Pressure required to inflate lung to a given volume is a function of air

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12
Q

dynamic compliance is a function of:

A

both airway resistance and the elasticity of the chest wall

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13
Q

Static Compliance

A

measures compliance when there is no airflow

Pressure required to keep lung inflated to a given volume is a function

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14
Q

static compliance is a function of:

A

elasticity of the chest wall only

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15
Q

Peak Inspiratory Pressure

A

max pressure in pt’s airway during inspiration

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16
Q

what factors affect PIP

A

airway resistance and chest/lung compliance (Pelastic)

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17
Q

measurement of dynamic compliance

A

PIP

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18
Q

Dynamic compliance =

A

Vt / PIP – PEEP

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19
Q

Pressure in small airways & alveoli after target Vt delivered

A

Plateau Pressure

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20
Q

what conditions decrease pulmonary compliance?

how does this affect the PP and PIP?

A
  • endobronchial intubation
  • pulmonary edema
  • pleural effusion
  • tension PTX
  • atelectasis

usually due to reduction in static compliance (PIP and PP increase)

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21
Q

what conditions increase pulmonary resistance?

how does this affect the PP and PIP?

A
  • kinked ETT
  • ETT cuff herniation
  • bronchospasm
  • bronchial secretions
  • airway compression
  • foreign body aspiration

usually due to reduction in dynamic compliance (increased PIP, PP unchan

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22
Q

phases of capnograph

A
  • I (A-B) = exhalation of anatomic dead space
  • II (B-C) = exhalation of anatomic dead space + alveolar gas
  • III (C-D) = exhalation of alveolar gas
  • IV (D-E) = inspiration of fresh gas that doesn’t contain CO2
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23
Q
A

A = P elastic
B = P plateau
C = P peak
D = P resistance

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24
Q

what is PIP?

A

max pressure in pt’s airway during inspiration

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25
Q

what is PIP affected by

A

airway resistance and chest/lung compliance (Pelastic)

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26
Q

what is plateau pressure

A

Pressure in small airways & alveoli after target Vt delivered

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27
Q

what does plateau pressure reflect?

A

elastic recoil of lungs & thorax during inspiratory pause (no gas moving in or out)

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28
Q

plateau pressure assoc. with barotrauma

A

> 35 cm H2O

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29
Q

complications of increased PP

A
  • VALI
  • PTX, pneumomediastinum
  • subcutaneous emphysema
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30
Q

how to reduce PP if barotrauma exists

A

↓ Vt, inspiratory flow, and PEEP (sedation also helpful)

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31
Q

normal static compliance for an adult

A

35-100 mL/cm H2O

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32
Q

normal static compliance for a child

A

> 15 mL/cm H2O

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33
Q

what does it mean if ↑ PIP with no change in PP

A

resistance has increased OR inspiratory flow rate has increased

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34
Q

what does it mean if ↑ PIP + ↑ PP

A

total compliance has decreased (Pelastic increased) OR Vt has increased

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35
Q

final product of aerobic metabolism

A

CO2

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36
Q

what is ventilation?

A

Once CO2 is in alveolus, ventilation is the process by which CO2 is eliminated from body

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37
Q

at what point of capnography waveform is EtCO2 measured?

A

point D

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38
Q

what does it mean if you see a small peak just before inspiration on capnograph waveform

A

reflects emptying of alveoli with longer time constants and higher CO2 concentrations

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39
Q

V/Q during phases II & III of EtCO2 waveform

A

II = increased V/Q in apex
III = decreased V/Q in bases

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40
Q

where is the alpha angle of capnograph waveform measured

A

point C

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41
Q

normal alpha angle of capnograph

A

100-110 degrees

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42
Q

causes of increased alpha angle

A

expiratory airflow obstruction (COPD, bronchospasm, kinked ETT)

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43
Q

where is beta angle measured in capnograph waveform

A

point D

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44
Q

angle of beta angle

A

90 degrees

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45
Q

cause of increased beta angle

A

rebreathing caused by faulty inspiratory valve

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46
Q

CO2 analysis that provides faster response time

A

mainstream (in-line)

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47
Q

which type of CO2 analysis increases apparatus dead space

A

mainstream (in-line)

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48
Q

why is the response time for a sidestream (diverting) CO2 analysis usually slower than mainstream

A

Pumping mechanism continuously aspirates gas sample from breathing circuit

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49
Q

what does this EtCO2 waveform represent

A

airflow obstruction

ex - COPD, bronchospasm, kinked ETT

50
Q

EtCO2 waveform with airway obstruction

A

prolonged upstroke with increased alpha angle

51
Q

what does this EtCO2 waveform represent

A

cardiac oscillations

caused by heart beating against lungs

52
Q

what does this EtCO2 waveform represent

A

cardiac oscillations

caused by heart beating against lungs

53
Q

what does this indicate if seen during spontaneous ventilation

A

inadequate muscle relaxant reversal

54
Q

what does this EtCO2 waveform represent & what causes it

A

low EtCO2 - plateau phase well below normal

Caused by hyperventilation, ↓ CO2 production, ↑ alveolar dead space

55
Q

examples of increased dead space that can cause this waveform

A

hypotension
PE

low EtCO2

56
Q

what does this waveform represent

A

increased EtCO2 with normal plateau

Caused by ↑ CO2 production or ↓ alveolar ventilation

  • Ex ↑ CO2: MH, sepsis, fever, hyperthyroid
  • Ex ↓ ventilation: hypoventilation, narcotics
57
Q

what does this waveform represent

A

increased EtCO2 with normal plateau

Caused by ↑ CO2 production or ↓ alveolar ventilation

  • Ex ↑ CO2: MH, sepsis, fever, hyperthyroid
  • Ex ↓ ventilation: hypoventilation, narcotics
58
Q

what does this waveform represent

A

inspired CO2 - baseline doesn’t return to 0, indicates rebreathing

59
Q

causes of an EtCO2 baseline that doesn’t return to zero

A
  • exhausted absorbent
  • incompetent expiratory valve
  • hole in inner tube of Bain
  • inadequate FGF with Mapleson
  • rebreathing under drapes (not intubated)
60
Q

what does this waveform represent

A

incompetent inspiratory valve

61
Q

EtCO2 waveform changes seen with incompetent inspiratory valve

A

Decreased slope during inspiratory phase (widened beta angle)

Waveform may or may not reach 0 (depends on FGF)

62
Q

EtCO2 waveform changes seen with incompetent inspiratory valve

A

Decreased slope during inspiratory phase (widened beta angle)

Waveform may or may not reach 0 (depends on FGF)

63
Q

what does this represent

A

leak in sample line during PPV

64
Q

EtCO2 changes with leak in sample line during PPV

A
  • Beginning of plateau is low - alveolar gas is diluted when atmospheric air is aspirated into sample line
  • Positive pressure during inspiration pushes CO2-rich gas through sample line - results in peak at the end of the plateau
65
Q

patient populations you might see this waveform in

A

obese and pregnant patients

66
Q

when can this waveform be seen

A

after single-lung transplant
* First peak is alveolar gas from transplanted lung (normal time constant)
* Second peak is alveolar gas from diseased lung (air trapped in sick lung = longer time constant)

Also reported with severe kyphoscoliosis

67
Q

4 requirements for EtCO2 to be detected

A
  1. CO2 must be produced during metabolism
  2. Must be adequate pulmonary blood flow to deliver CO2 to lungs for elimination
  3. Must be adequate ventilation to transport CO2 to breathing circuit
  4. Must be intact sampling system
68
Q

what 2 things should be considered to answer a question about changes in EtCO2

A
  1. what is the cause
  2. does this affect the PaCO2-EtCO2 gradient
69
Q

causes of wide PaCO2 to EtCO2 gradient

A

suggests V/Q mismatch or equipment malfunction

70
Q

normal PaCO2 to EtCO2 gradient

A

2-5 mmHg

71
Q

causes of increased EtCO2 r/t increased CO2 production and delivery to lungs

A
  • increased BMR (↑ VO2)
  • MH
  • thyrotoxicosis
  • fever
  • sepsis
  • seizures
  • laparoscopy
  • tourniquet or vascular clamp removal
  • bicarb admin
  • shivering
  • increased muscle tone (NMB reversal)
  • medication side effect
72
Q

causes of increased EtCO2 r/t decreased alveolar ventilation

A
  • hypoventilation
  • CNS depression
  • residual NMB
  • COPD
  • high spinal
  • neuromuscular disease
  • metabolic alkalosis (if SV)
  • medication side effect
73
Q

3 changes that affect EtCO2

A
  1. CO2 production and delivery to lungs
  2. alveolar ventilation
  3. equipment
74
Q

equipment malfunctions that increase EtCO2

A

rebreathing, CO2 absorbent exhaustion, unidirectional valve malfunction, increased apparatus dead space

75
Q

decreased EtCO2 r/t decreased CO2 production and delivery to lungs

A
  • decreased BMR (↓ VO2)
  • ↑ anesthetic depth
  • hypothermia
  • ↓ pulmonary blood flow
  • ↓ CO
  • hypotension
  • PE
  • V/Q mismatch
  • medication side effect
  • pain/anxiety (if breathing spontaneously)
76
Q

equipment malfunctions that cause decreased etco2

A

ventilator disconnect, esophageal intubation, poor seal with LMA or ETT, sample line leak, airway obstruction, apnea

77
Q

what wavelengths of light are emitted by a pulse ox

A

red light (660 nm) and near-infrared light (940 nm)

78
Q

Beer Lambert law applied to pulse ox

A

relates intensity of light transmitted through a solution and concentration of solute within the solution

solution = blood, solute = Hgb

79
Q

red light is preferentially absorbed by:

A

deoxyhemoglobin (venous blood has relatively more than arterial)

80
Q

Near-infrared light is preferentially absorbed by:

A

oxyhemoglobin (arterial has more)

81
Q

which has a higher wavelength and higher amount of bound O2: red or near-infrared light?

A

near-infrared

82
Q

where is the greatest amount of blood in tissue sample at pulse ox trough

A

venous

83
Q

where is the greatest amount of blood in tissue sample at pulse ox peak

A

arterial

84
Q

SpO2 =

A
85
Q

SpO2 =

A
86
Q

pulse ox sites that are fast, middle, and slow

A
  • Fast = ear, nose, tongue, esophagus, forehead
  • Middle = finger
  • Slow = toe
87
Q

pulse ox placements that can cause venous engorgement and falsely decreased SpO2 in trendelenburg

A

head or esophagus

88
Q

when is SpO2 monitoring most useful

A

when the patient’s PaO2 aligns with steep portion of oxyhgb dissociation curve

89
Q

causes of oxyhgb dissociation curve LEFT shift

A
  • ↓ temp
  • ↓ 2,3-DPG
  • ↓ CO2
  • ↓ H+
  • ↑ pH
  • ↑ HgbMet
  • ↑ HgbCO
  • ↑ Hgb F

left = love (increased affinity for O2)

90
Q

causes right shift of oxyhgb dissociation curve

A
  • ↑ temp
  • ↑ 2,3-DPG
  • ↑ CO2
  • ↑ H+
  • ↓ pH

right = release (decreasd affinity for O2)

91
Q

SpO2 90, 80, 70 = PaO2 ?

A

60, 50, 40

92
Q

Methods to improve SpO2 signal

A

digital block, warm extremity, protect from ambient light, apply vasodilating cream, administer arterial vasodilator

93
Q

a pulse ox is a noninvasive monitor of what 3 things

A
  • Hgb saturation
  • HR
  • Fluid responsiveness (pulse pressure variation)
94
Q

1st branch off aortic arch

A

Brachiocephalic (innominate) artery

3rd branch off aorta

95
Q

1st branch off aortic arch

A

Brachiocephalic (innominate) artery

3rd branch off aorta

96
Q

SpO2 in severe anemia

A

pulse ox may overestimate - SpO2 does not quanitify amount of Hgb or dissolved O2 in blood

97
Q

where can pulse ox be placed to monitor perfusion during mediastinoscopy

A

right extremity

perfusion index & waveform quality will be affected if brachiocephalic artery is compressed by scope

98
Q

alveolar ventilation in a patient hypoventilating on room air

A

According to alveolar gas equation, will have increased alveolar PCO2 and decreased alveolar PO2

99
Q

alveolar oxygen calculation

A
100
Q

alveolar oxygen calculation

A
101
Q

T/F pulse ox is a reliable measure for detecting bronchial intubation

A

false

if a high inspired O2 concentration is used, it’s possible SpO2 will be

102
Q

T/F pulse ox is a reliable measure for detecting bronchial intubation

A

false

if a high inspired O2 concentration is used, it’s possible SpO2 will be

103
Q

best assessments of bronchial intubation

A

Better assessed by bilateral breath sounds, CXR, and/or fiberoptic visualization of carina

104
Q

margin of error for SpO2

A

+/- 2-3% when SpO2 70-100%
3% when SpO2 50-70%

105
Q

required to diagnose methemoglobin or carboxyhemoglobin

A

co-oximeter

106
Q

SpO2 with methemoglobin

A
  • absorbs 660 nm and 940 nm equally - 1:1 absorption ratio is read as 85%
  • Falsely underestimates SpO2 if O2 sat > 85%
  • Falsely overestimates SpO2 if O2 sat < 85%
107
Q

SpO2 in carboxyhemoglobin

A
  • absorbs 660 nm to same degree as OxyHgb
  • Co-Hgb & Oxyhgb look the same to the pulse ox
  • Reads sum of Co-Hgb + Oxyhgb (overestimates SpO2)
108
Q

how does nail polish affect SpO2

A

black, blue, and green affect accuracy

red & purple do not

109
Q

dyes that can affect spo2 accuracy

A

methylene blue
indocyanine green
indigo carmine

NOT fluorescein

110
Q

determines concentrations and identities of all the sample gases simultaneously

A

Infrared Absorption Spectrophometry

111
Q

does oxygen absorb infrared light

A

nope

112
Q

how is exhaled oxygen measured

A

must be measured by electrochemical analysis (galvanic cell or Clark electrode) or paramagnetic analysis

113
Q

what is mass spectometry

A
  • Bombards a gas sample with electrons creating ion fragments
  • All particles become charged & can be separated and identified based on their mass
114
Q

Uses a high-power argon laser to produce photons

A

Raman Scatter Spectrometry

115
Q

New tool that can detect inspired, expired, and breath to breath changes of a particular gas by incorporating a lipid layer on the crystal

A

Piezoelectric Crystals

Lipid layer responds to individual gases as they make contact and get ab

116
Q

New tool that can detect inspired, expired, and breath to breath changes of a particular gas by incorporating a lipid layer on the crystal

A

Piezoelectric Crystals

Lipid layer responds to individual gases as they make contact and get ab

117
Q

why are Piezoelectric Crystals impractical in the clinical setting

A

Unable to identify multiple gases at once

118
Q

how does hypocapnia affect oxyhgb dissociation curve

A

left shift

119
Q

how does hypercapnia affect oxyhgb dissociation curve

A

right shift

120
Q

what can infrared absorption spectrophometry measure? what can’t it measure?

A

CAN measure CO2, N2O, volatiles

CAN’T measure O2, helium, nitrogen, xenon

121
Q

most likely cause of acute decrease in EtCO2

A

hypovolemia (increased dead space)

ex - hemorrhage

122
Q

most likely cause of acute decrease in EtCO2

A

hypovolemia (increased dead space)

ex - hemorrhage

123
Q

relationship between PaCO2-EtCO2 gradient and dead space

A

increased gradient = increased dead space

APEX (54 decks)

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