Unit 6 - Respiratory Monitors & Equipment Flashcards
1
Q
formula for dynamic compliance
A
Vt / PIP - PEEP
2
Q
which phase of the capnograph waveform best correlates to V/Q status
A
phase III
3
Q
what point of capnograph is EtCO2 measured
A
point D
4
Q
what gases can infrared analysis measure
A
- N2O
- CO2
- volatiles
NOT O2, helium, Nitrogen, or xenon
4
Q
what gases can infrared analysis measure
A
- N2O
- CO2
- volatiles
NOT O2
5
Q
handwritten notes - paco2 to etco2 gradient
A
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
7
Q
Airway Resistance =
A
[P (airway) – P (alveolar)] / Gas Flow Rate
8
Q
Airway Compliance =
A
change in volume / change in pressure
9
Q
factors that influence airway compliance
A
- muscle tone
- degree of lung inflation
- alveolar surface tension
- amount of interstitial lung water
- pulmonary fibrosis
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
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
12
Q
dynamic compliance is a function of:
A
both airway resistance and the elasticity of the chest wall
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
14
Q
static compliance is a function of:
A
elasticity of the chest wall only
15
Q
Peak Inspiratory Pressure
A
max pressure in pt’s airway during inspiration
16
Q
what factors affect PIP
A
airway resistance and chest/lung compliance (Pelastic)
17
Q
measurement of dynamic compliance
A
PIP
18
Q
Dynamic compliance =
A
Vt / PIP – PEEP
19
Q
Pressure in small airways & alveoli after target Vt delivered
A
Plateau Pressure
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)
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
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
23
Q
A
A = P elastic
B = P plateau
C = P peak
D = P resistance
24
what is PIP?
max pressure in pt’s airway during inspiration
25
what is PIP affected by
airway resistance and chest/lung compliance (Pelastic)
26
what is plateau pressure
Pressure in small airways & alveoli after target Vt delivered
27
what does plateau pressure reflect?
elastic recoil of lungs & thorax during inspiratory pause (no gas moving in or out)
28
plateau pressure assoc. with barotrauma
> 35 cm H2O
29
complications of increased PP
* VALI
* PTX, pneumomediastinum
* subcutaneous emphysema
30
how to reduce PP if barotrauma exists
↓ Vt, inspiratory flow, and PEEP (sedation also helpful)
31
normal static compliance for an adult
35-100 mL/cm H2O
32
normal static compliance for a child
> 15 mL/cm H2O
33
what does it mean if ↑ PIP with no change in PP
resistance has increased OR inspiratory flow rate has increased
34
what does it mean if ↑ PIP + ↑ PP
total compliance has decreased (Pelastic increased) OR Vt has increased
35
final product of aerobic metabolism
CO2
36
what is ventilation?
Once CO2 is in alveolus, **ventilation** is the process by which CO2 is eliminated from body
37
at what point of capnography waveform is EtCO2 measured?
point D
38
what does it mean if you see a small peak just before inspiration on capnograph waveform
reflects emptying of alveoli with longer time constants and higher CO2 concentrations
39
V/Q during phases II & III of EtCO2 waveform
II = increased V/Q in apex
III = decreased V/Q in bases
40
where is the alpha angle of capnograph waveform measured
point C
41
normal alpha angle of capnograph
100-110 degrees
42
causes of increased alpha angle
expiratory airflow obstruction (COPD, bronchospasm, kinked ETT)
43
where is beta angle measured in capnograph waveform
point D
44
angle of beta angle
90 degrees
45
cause of increased beta angle
rebreathing caused by faulty inspiratory valve
46
CO2 analysis that provides faster response time
mainstream (in-line)
47
which type of CO2 analysis increases apparatus dead space
mainstream (in-line)
48
why is the response time for a sidestream (diverting) CO2 analysis usually slower than mainstream
Pumping mechanism continuously aspirates gas sample from breathing circuit
49
what does this EtCO2 waveform represent
airflow obstruction
| ex - COPD, bronchospasm, kinked ETT
50
EtCO2 waveform with airway obstruction
prolonged upstroke with increased alpha angle
51
what does this EtCO2 waveform represent
cardiac oscillations
| caused by heart beating against lungs
52
what does this EtCO2 waveform represent
cardiac oscillations
| caused by heart beating against lungs
53
what does this indicate if seen during spontaneous ventilation
inadequate muscle relaxant reversal
54
what does this EtCO2 waveform represent & what causes it
low EtCO2 - plateau phase well below normal
Caused by hyperventilation, ↓ CO2 production, ↑ alveolar dead space
55
examples of increased dead space that can cause this waveform
hypotension
PE
| low EtCO2
56
what does this waveform represent
increased EtCO2 with normal plateau
Caused by ↑ CO2 production or ↓ alveolar ventilation
## Footnote
* Ex ↑ CO2: MH, sepsis, fever, hyperthyroid
* Ex ↓ ventilation: hypoventilation, narcotics
57
what does this waveform represent
increased EtCO2 with normal plateau
Caused by ↑ CO2 production or ↓ alveolar ventilation
## Footnote
* Ex ↑ CO2: MH, sepsis, fever, hyperthyroid
* Ex ↓ ventilation: hypoventilation, narcotics
58
what does this waveform represent
inspired CO2 - baseline doesn't return to 0, indicates rebreathing
59
causes of an EtCO2 baseline that doesn't return to zero
* exhausted absorbent
* incompetent expiratory valve
* hole in inner tube of Bain
* inadequate FGF with Mapleson
* rebreathing under drapes (not intubated)
60
what does this waveform represent
incompetent inspiratory valve
61
EtCO2 waveform changes seen with incompetent inspiratory valve
Decreased slope during inspiratory phase (widened beta angle)
## Footnote
Waveform may or may not reach 0 (depends on FGF)
62
EtCO2 waveform changes seen with incompetent inspiratory valve
Decreased slope during inspiratory phase (widened beta angle)
## Footnote
Waveform may or may not reach 0 (depends on FGF)
63
what does this represent
leak in sample line during PPV
64
EtCO2 changes with leak in sample line during PPV
* 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
patient populations you might see this waveform in
obese and pregnant patients
66
when can this waveform be seen
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)
## Footnote
Also reported with severe kyphoscoliosis
67
4 requirements for EtCO2 to be detected
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
what 2 things should be considered to answer a question about changes in EtCO2
1. what is the cause
2. does this affect the PaCO2-EtCO2 gradient
69
causes of wide PaCO2 to EtCO2 gradient
suggests V/Q mismatch or equipment malfunction
70
normal PaCO2 to EtCO2 gradient
2-5 mmHg
71
causes of increased EtCO2 r/t increased CO2 production and delivery to lungs
* 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
causes of increased EtCO2 r/t decreased alveolar ventilation
* hypoventilation
* CNS depression
* residual NMB
* COPD
* high spinal
* neuromuscular disease
* metabolic alkalosis (if SV)
* medication side effect
73
3 changes that affect EtCO2
1. CO2 production and delivery to lungs
2. alveolar ventilation
3. equipment
74
equipment malfunctions that increase EtCO2
rebreathing, CO2 absorbent exhaustion, unidirectional valve malfunction, increased apparatus dead space
75
decreased EtCO2 r/t decreased CO2 production and delivery to lungs
* decreased BMR (↓ VO2)
* ↑ anesthetic depth
* hypothermia
* ↓ pulmonary blood flow
* ↓ CO
* hypotension
* PE
* V/Q mismatch
* medication side effect
* pain/anxiety (if breathing spontaneously)
76
equipment malfunctions that cause decreased etco2
ventilator disconnect, esophageal intubation, poor seal with LMA or ETT, sample line leak, airway obstruction, apnea
77
what wavelengths of light are emitted by a pulse ox
red light (660 nm) and near-infrared light (940 nm)
78
Beer Lambert law applied to pulse ox
relates intensity of light transmitted through a solution and concentration of solute within the solution
solution = blood, solute = Hgb
79
red light is preferentially absorbed by:
deoxyhemoglobin (venous blood has relatively more than arterial)
80
Near-infrared light is preferentially absorbed by:
oxyhemoglobin (arterial has more)
81
which has a higher wavelength and higher amount of bound O2: red or near-infrared light?
near-infrared
82
where is the greatest amount of blood in tissue sample at pulse ox trough
venous
83
where is the greatest amount of blood in tissue sample at pulse ox peak
arterial
84
SpO2 =
85
SpO2 =
86
pulse ox sites that are fast, middle, and slow
* Fast = ear, nose, tongue, esophagus, forehead
* Middle = finger
* Slow = toe
87
pulse ox placements that can cause venous engorgement and falsely decreased SpO2 in trendelenburg
head or esophagus
88
when is SpO2 monitoring most useful
when the patient’s PaO2 aligns with steep portion of oxyhgb dissociation curve
89
causes of oxyhgb dissociation curve LEFT shift
* ↓ temp
* ↓ 2,3-DPG
* ↓ CO2
* ↓ H+
* ↑ pH
* ↑ HgbMet
* ↑ HgbCO
* ↑ Hgb F
## Footnote
left = love (increased affinity for O2)
90
causes right shift of oxyhgb dissociation curve
* ↑ temp
* ↑ 2,3-DPG
* ↑ CO2
* ↑ H+
* ↓ pH
## Footnote
right = release (decreasd affinity for O2)
91
SpO2 90, 80, 70 = PaO2 ?
60, 50, 40
92
Methods to improve SpO2 signal
digital block, warm extremity, protect from ambient light, apply vasodilating cream, administer arterial vasodilator
93
a pulse ox is a noninvasive monitor of what 3 things
* Hgb saturation
* HR
* Fluid responsiveness (pulse pressure variation)
94
1st branch off aortic arch
Brachiocephalic (innominate) artery
| 3rd branch off aorta
95
1st branch off aortic arch
Brachiocephalic (innominate) artery
| 3rd branch off aorta
96
SpO2 in severe anemia
pulse ox may overestimate - SpO2 does not quanitify amount of Hgb or dissolved O2 in blood
97
where can pulse ox be placed to monitor perfusion during mediastinoscopy
right extremity
perfusion index & waveform quality will be affected if brachiocephalic artery is compressed by scope
98
alveolar ventilation in a patient hypoventilating on room air
According to **alveolar gas equation**, will have increased alveolar PCO2 and decreased alveolar PO2
99
alveolar oxygen calculation
100
alveolar oxygen calculation
101
T/F pulse ox is a reliable measure for detecting bronchial intubation
false
| if a high inspired O2 concentration is used, it’s possible SpO2 will be
102
T/F pulse ox is a reliable measure for detecting bronchial intubation
false
| if a high inspired O2 concentration is used, it’s possible SpO2 will be
103
best assessments of bronchial intubation
Better assessed by bilateral breath sounds, CXR, and/or fiberoptic visualization of carina
104
margin of error for SpO2
+/- 2-3% when SpO2 70-100%
3% when SpO2 50-70%
105
required to diagnose methemoglobin or carboxyhemoglobin
co-oximeter
106
SpO2 with methemoglobin
* 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
SpO2 in carboxyhemoglobin
* 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
how does nail polish affect SpO2
black, blue, and green affect accuracy
red & purple do not
109
dyes that can affect spo2 accuracy
methylene blue
indocyanine green
indigo carmine
| NOT fluorescein
110
determines concentrations and identities of all the sample gases simultaneously
Infrared Absorption Spectrophometry
111
does oxygen absorb infrared light
nope
112
how is exhaled oxygen measured
must be measured by electrochemical analysis (galvanic cell or Clark electrode) or paramagnetic analysis
113
what is mass spectometry
* Bombards a gas sample with electrons creating ion fragments
* All particles become charged & can be separated and identified based on their mass
114
Uses a high-power argon laser to produce photons
Raman Scatter Spectrometry
115
New tool that can detect inspired, expired, and breath to breath changes of a particular gas by incorporating a lipid layer on the crystal
Piezoelectric Crystals
| Lipid layer responds to individual gases as they make contact and get ab
116
New tool that can detect inspired, expired, and breath to breath changes of a particular gas by incorporating a lipid layer on the crystal
Piezoelectric Crystals
| Lipid layer responds to individual gases as they make contact and get ab
117
why are Piezoelectric Crystals impractical in the clinical setting
Unable to identify multiple gases at once
118
how does hypocapnia affect oxyhgb dissociation curve
left shift
119
how does hypercapnia affect oxyhgb dissociation curve
right shift
120
what can infrared absorption spectrophometry measure? what can't it measure?
CAN measure CO2, N2O, volatiles
CAN'T measure O2, helium, nitrogen, xenon
121
most likely cause of acute decrease in EtCO2
hypovolemia (increased dead space)
| ex - hemorrhage
122
most likely cause of acute decrease in EtCO2
hypovolemia (increased dead space)
| ex - hemorrhage
123
relationship between PaCO2-EtCO2 gradient and dead space
increased gradient = increased dead space
