Respiratory Flashcards
(155 cards)
1
Q
On traditional lung ultrasound, “lung sliding” is more commonly known as what sign?
A
Glide sign
2
Q
When it comes to lung ultrasound and a glide sign, the principle of lung sliding is based on 2 key concepts. What are they?
A
1 the parietal and visceral pleural are in their normal anatomic locations
#2 lung sliding is dynamic and occurs only when the patient breathes
3
Q
The absence of lung sliding has a specificity of __ to __% for the diagnosis of pneumothorax in people.
A
88-98%
4
Q
T/F: The true sensitivity and specificity of absent lung sliding to diagnose pneumothorax in small animal patients remains unknown
A
true
5
Q
What are the 5 criteria that define a B line?
A
1 they are unfading vertical white lines
#2 they originate at the lung surface
#3 they move in synchrony with lung sliding
#4 they extend into the far field
#5 they obscure A lines if present
(#1-3 are obligatory whereas #4-5 are not always present)
6
Q
Definition/Ultrasound Sign: The rhythmic movement of the visceral pleura in opposition to the parietal in synchrony with the cardiac rhythm
A
lung pulse (when present it rules out PTX)
7
Q
Definition/Ultrasound Sign: The site within the thorax where the visceral pleura of the lung recontacts the parietal pleura of the thoracic wall in patients with pneumothorax
A
Lung point
8
Q
Definition/Ultrasound Sign: (Rare, not yet reported in vet med) Detected with both edges of trapped pleural air can be scanned and visualized as 2 lung points alternating on the 2 opposite sides of the probe moving in opposite directions
A
double lung point
9
Q
What is the ESSENTIAL feature of a double lung point (ultrasound finding)?
A
the lung points appear to move in opposite directions
10
Q
Definition/Ultrasound Sign: Movement of A lines in the opposite direction to classic lung sliding during inspiration (only seen on dogs under anesthesia experimentally)
A
Reverse sliding sign
11
Q
Definition/Ultrasound Sign:A vertical edge artifact created when air overlies soft tissue structures or less commonly pleural effusion within the thorax. Usually its visualized at the caudal border of the lung near the diaphragm
A
normal curtain sign
12
Q
Definition/Ultrasound Sign: Defined as the movement of the vertical air edge artifact (pneumothorax induced) in the OPPOSITE direction of abdominal contents
A
asynchronous curtain sign
13
Q
Definition/Ultrasound Sign: Horizontal lines that originate from the pulmonary-pleural line. Air reverberation artifacts
A
A lines
14
Q
Definition/Ultrasound Sign: Alveoli filled with edema. Move in synchrony with phases of respiration
A
B line
15
Q
What are the sites of Vet BLUE?
A
Caudodorsal (Cd)
Perihilar (Ph)
Middle (Md)
Cranial (Cr)
DH view
*9 total, left and right + DH
16
Q
What does VetFAST-ABCDE stand for…
A
Veterinary focused assessment with sonography for trauma - airway, breathing, circulation, disability, and exposure
17
Q
VetFAST-ABCDE is an adaptation of human POC emergency ultrasound to assess thoracic and abdominal injury, CV status and what other organ?
A
optic nerve diameter to assess for changes in ICP
18
Q
What is the major limitation of VetFAST-ABCDE?
A
Probe is only used to image intercostal spaced 4-9
19
Q
In a study by Dicker at al (JVECC 2020) comparing the diagnosis of pulmonary contusions using Vet BLUE, TXR and thoracic CT, did Vet BLUE had a higher or lower sensitivity than TXR for diagnosis of pulmonary contusions?
A
Higher (90.5% sensitive and 87.5% specific)
20
Q
What are general limitations of lung ultrasound?
A
1 can only image lung pathology that reaches lung periphery
21
Q
Definition/Ultrasound Finding: Vertical hyper echoic beams similar to B lines that origination from air in the SQ
A
E lines
22
Q
Global FAST incorporates what two imaging protocols?
A
TFAST echocardiography and Vet Blue
23
Q
If a patient is fluid responsive, what will you observe in the CVC between the phases of respiration?
A
35-50% change in height of CVC
24
Q
For each Vewt BLUE site, how many ICS spaces should be surveyed?
A
3 ICS at each site
25
What is the Vet BLUE B line scoring system?
0 (no B lines)
1 (single B line)
2 (2 B lines)
3 (3 B lines)
greater than 3 (more than 3 B lines)
Infinity (confluent over enter ICS)
*performed by taking the highest number of B lines over a single ICS at each site
26
What does AIS stand for?
alveolar interstitial syndrome (basically what B lines are, alveolar interstitial edema)
27
Does lung fibrosis create true or pseudo-B lines?
Pseudo-B lines
(True B lines imply fluid which is not present with fibrosis)
28
Definition/Ultrasound Finding: Hyperechoic foci within consolidated lung with irregular borders in the far field
shred sign
29
Definition/Ultrasound Finding: Complete lack of aeration within consolidated lung; hepatized lung
tissue sign
30
Definition/Ultrasound Finding: Aerated alveoli cuffing soft tissue characterized by hypoechoic or anechoic oval or circle with hyperechoic far border
nodule sign
31
Definition/Ultrasound Finding: Combination of the shred and tissue signs and represents lung infarction
wedge sign
(can be hard to differentiate between shred and pneumonia)
32
Definition: Mismatch between the patient's own inspiratory and expiratory times and the mechanical ventilator delivery times
dyssynchrony
33
What are the effects of MV dyssynchrony?
Overload respiratory muscles
Increased alveolar dissension w/ risk of lung injury
Compromise sleep quality resulting in increased sedation/delirium
34
What are the categories of patient ventilatory dyssynchrony?
#1 Dyssynchrony of the trigger phase (delayed and ineffective efforts, auto triggering)
#2 Dyssynchrony of the flow phase
#3 Dyssynchrony of the cycling phase (premature cycling off, delayed cycling off)
#4 Reverse triggering
35
What is the type of dyssynchrony where the patient attempts to start a breath but the ventilator trigger fails?
Ineffective efforts
(the ventilator is unable to detect the patient's effort so the inspiratory phase of the mechanically delivered breath is not started)
36
What is the gold standard to assess ineffective triggering during MV?
#1 negative deflection in esophageal pressure (Pes)
#2 significant increase in electrical activity of the diaphragm
(neither of these are practical)
37
What is a practical way of assessing ineffective triggering during MV (compared to gold standard)?
decrease in airway pressure-time waveform along with an increase in airflow during expiration
(the increase in flow is small and is the patient trying to take and breath, but no MV breath follows it)
38
What type of dyssynchrony results in delay between the start of the neural and mechanical inspiration?
triggering delay
39
What is the most important cause of ineffective efforts and delayed triggering related to patient disease?
the presence of dynamic hyperinflation that generates intrinsic PEEP (PEEPi)
(Can think of it like breath stacking; the patient's ventilatory muscles must first counterbalance PEEPi in the alveoli before the ventilator senses any variation in flow or pressure and then triggers the next breath)
40
The most important cause of ineffective efforts and delayed triggering related to patient disease is the presence of dynamic hyperinflation that generates intrinsic PEEP (PEEPi). How will this appear on a flow waveform?
An abrupt expiratory flow end before a triggered breath
41
What type of dyssynchrony occurs where the patient makes no attempt at breathing and the ventilator will trigger a breath on its own?
autotriggering
42
What are causes of auto triggering?
(anything that causes a change in pressure or flow by the ventilatory that is unrelated to patient efforts)
circuit leaks
very sensitive trigger settings that will activate from thoracic pressure changes in the cardiac cycle (more common with cardiac pacing)
43
In a patient triggered breath, will you see an increase, decrease, or no change in airway pressure prior to the start of the ventilator breath?
decrease in airway pressure (normal)
44
What type of dyssynchrony results in insufficient flow delivery too low for the patient's respiratory need?
dyssynchrony of the flow phase
45
In a patient that has a relative flow starvation, what will you see during the inspiration phase in the airway pressure curve?
airway pressure falls giving the pressure time curve a scooped out look which can be severe enough to decrease peak airway pressure
46
What type of dyssynchrony occurs when the neural inspiratory time and the ventilator inspiratory time are mismatched?
cycling dyssynchrony
47
What type of dyssynchrony occurs when the mechanical inspiratory time (Ti) is shorter than the neural Ti leaving the patient air hungry?
short cycling dyssynchrony
48
When short cycling dyssynchrony is bad enough, what other type of dyssynchrony can occur?
double triggering (aka breath stacking)
49
What type of dyssynchrony results in a second mechanical breath being triggered before full deflation of the first one?
double triggering (aka breath stacking)
50
What is the major consequence of double triggering dyssynchrony?
increased total tidal volume
51
What is the most common dyssynchrony and the incidence worsens with lung injury and high respiratory drive?
double triggering (aka breath stacking)
52
What is the detrimental effect of an inverse ratio?
increasing mean airway pressure (worsens lung injury)
53
What type of dyssynchrony results is a longer ventilator inspiratory time than patient neural inspiratory time?
delayed cycling off
54
With delayed cycling off, this can be recognized by what change in the airway pressure curve?
abrupt spike in airway pressure near the end of mechanical inspiration on the pressure time waveform
55
Premature or delayed cycling can be minimized by adjusting what in pressure support ventilation?
adjusting the pressure rise time (increase if delayed cycling)
56
What is the oxygenation goal (PaO2 and SpO2) during MV?
PaO2 55-80 mm Hg
SpO2 88-95%
57
What is normal respiratory compliance?
100 ml/cm H2O
58
Definition: the change in lung volume per unit change in pressure in the absence of flow
static compliance
59
Definition: The change in volume divided by change in pressure, measured during normal breathing, between points of apparent zero flow at the beginning and end of inspiration
dynamic compliance
60
What are the components of static compliance?
chest wall compliance
lung tissue compliance
61
What are the components of dynamic compliance?
chest wall compliance
lung tissue compliance
airway resistance
62
Term used to describe the difference between inspiratory and expiratory compliance
hysteresis
63
What are factors that cause decreased lung compliance
loss of surfactant
decreased elasticity (eg. pulmonary edema, fibrosis)
decreased functional lung volume (eg. pneumonia, pneumo)
alveolar derecruitment
alveolar overdistension
64
What is the equation for resistance?
Change in pressure/Flow
65
What is the equation for compliance?
change in volume/change in pressure
66
Compliance is optimal at what point on the classic lung compliance curve (with all the different volumes of air in a breath)?
compliance is optimal just above FRC (compliance is poor at low and high volumes)
67
Define hysteresis
Lung volume at any given pressure during inhalation is less than the lung volume at any given pressure during exhalation
68
Describe the effect of surface tension on hysteresis.
Surface tension in a deflated lung is lower than in a fully inflated lung because the molecules of alveolar surfactant are packed closer together, increasing their concentration at the gas-liquid interface and thereby decreasing surface tension.
These phospholipid molecules on the surface of well-stretched alveoli are further apart, which increases the surface tension and makes the lung less compliant.
Thus, after fully inflating the lung, the deflation curve has a lower compliance (i.e. there is little change in volume over a substantial change in pressure)
69
Why are collapsed alveoli more difficult to open than well inflated alveoli?
because collapsed alveoli are less elastic and require more mechanical energy to open (recruitment and derecruitment)
70
What is the equation for dynamic compliance?
TV / (PIP - PEEP)
(*but this is not entirely accurate since resistance is included in the measurement; the machine measures it during a point at which gas flow is close to zero and PIP may be replaced with P1 - the pressure shortly after cessation of flow which is slightly higher than the plateau pressure)
71
T/F: Dynamic compliance is always lower than static compliance
true
72
What is the main difference between static and dynamic compliance?
resistance
73
Dynamic compliance will decrease with (DECREASING/INCREASING) airflow and (SLOWER/FASTER) respiratory cycle.
increasing airflow and faster respiratory cycle (this is called frequency dependence)
74
What are 6 factors that influence lung compliance?
lung volume (PEEP, dynamic hyperinflation)
lung elastic recoil (affected by age and disease states)
chest wall compliance
pulmonary blood volume (a congested lung is less compliant)
lung surfactant
posture
*respiratory rate (dynamic compliance only)
75
What is the name for the pressure gradient that allows gas flow in and out of the lungs?
transrespiratory pressure
76
What is the name of the portion of the airway that does not participate in gas exchange?
conductive airway
77
What portion of the respiratory tract makes up alveolar volume?
the respiratory airway (part that participates in gas exchange)
78
What is the name of the pressure that is needed to overcome the resistance of the conductive airway for gas to get into the alveoli?
transairway pressure
79
What is the name for the pressure needed to expand the alveoli to allow air in for gas exchange?
transthoracic pressure
80
What is the pressure needed to maintain alveolar inflation?
transpulmonary pressure
81
Transrespiratory pressure is a sum of what two other pressures?
transrespiratory pressure = transairway pressure + transthoracic pressure
(https://www.fizzicu.com/post/equation-of-motion-how-we-get-air-into-our-lungs)
82
What type of diseases result in high resistance and normal compliance?
COPD
asthma
Ventilatory tubing blockage or kink
Conducive airway blockage (secretions)
83
What type of diseases result in normal resistance but low compliance?
ARDS
Pneumonia
Pulmonary edema
Pneumothorax
Pleural effusion
Obesity
Abdominal compartment syndrome
Ventilatory dyssynchrony
84
What is the equation for static compliance?
TV/(Pplat - PEEP)
85
What is the equation for resistance?
(PIP - Pplat) / F
86
If both PIP and Pplat are elevated, is it a resistance or compliance issue?
compliance
87
If PIP is elevated but Pplat is normal, is it a resistance or compliance issue?
resistance
88
What is normal resistance?
< 15 cm H2O/L/s
89
What is normal static compliance?
60-100 mL/cm H2O
90
What is normal dynamic compliance?
50-80 mL/cm H2O
91
If measured PEEP is higher than the set PEEP, what does this mean?
air-trapping, auto-PEEP, vent dyssynchrony
(the previous breath was not completely exhaled)
92
What do you call the graph of flow, pressure, or volume OVER time?
scalar
93
The amount of pressure required to inflate the lung depends on what two patient factors?
compliance
resistance
94
In volume controlled ventilation with constant flow, which scalar will have a rectangular shape?
flow
95
In pressure controlled ventilation, the flow scalar will have what type of shape?
descending curve
96
What type of loop can be used to evaluate changes in lung compliance?
pressure volume
97
During a mechanical breath, which direction will the PV loop track?
counter clockwise
98
During a spontaneous breath, which direction will the PV loop track?
clockwise
99
Can scalars or loops be used to assess the mode of ventilation being used?
scalars
100
T/F: When the flow is at zero, the pressure gradient between the ventilator and patient's lungs are the same
true
101
In pressure controlled breaths, what two factors are dependent on patient effort?
flow
tidal volume
(this is why we see such a difference in the flow scalar during pressure controlled ventilation between a patient triggered breath and machine triggered breath)
102
During volume targeted ventilation, as compliance decreases, what happens to airway pressure?
airway pressure increases (remember its VC so volume will remain constant)
103
During pressure targeted ventilation, as compliance decreases, what happens to volume?
lung volume decreases
104
On a flow volume loop, a reduction in peak expiratory flow rate is most often associated with what problem?
airway obstruction
105
What does APRV stand for (ventilation mode)?
airway pressure release ventilation
106
What is the main goal of APRV compared to other modes of ventilation?
inversing high pressure time to low pressure time and generating auto-PEEP on purpose
107
What does "beaking" represent?
alveolar overdistension
108
What are the x and y axis of volumetric capnography?
expired CO2
exhaled lung volume
109
What are the components of respiratory dead space?
alveolar dead space
anatomic dead space (aka airway dead space)
110
What are two mechanisms leading to alveolar dead space?
#1 - over inflation (from hyperinflation, too high PEEP, too large TV)
#2 - decreased pulmonary perfusion (direct obstruction of arterial pulmonary vessel, reduction of output from RV)
111
How many phases are there on volumetric capnography?
3
112
What are the three phases of volumetric capnography?
1 - exhaled TV from airways not in contact with alveoli (no CO2)
2 - transition from anatomic and alveolar gas emptying (linear increase in CO2)
3 - slope of CO2 plateaus, represents pure alveolar gas
113
What is the main advantage of using volumetric capnography in the setting of mechanical ventilation?
measurement of dead space (helps to assess shunt fracture, best PEEP, mortality)
114
What are the benefits of prone position in MV?
redistributes perfusion
improved lung recruitment (and therefore V/Q homogeneity, oxygenation, reduced PaCO2)
115
Volumetric capnographic alveolar dead space fraction less than what % in conjunction with D dimers, increases the sensitivity of pulmonary embolism detection to 98.4%.
less than 20%
116
What is the Fick equation for cardiac output?
Q = VCO2 / (CvCO2 - CaCO2)
(Q = pulmonary capillary blood flow
VCO2 = CO2 eliminated per min
CvCO2 = CO2 content of mixed venous blood
CaCO2 = CO2 content of arterial blood)
117
Definition: the volume of air entering the lungs with each inspiration
tidal volume
118
The volume measure of air inspired per minute
minute ventilation
119
During inspiration, what is the pressure gradient between the mouth and alveolus?
-3 to -5 cm H2O
120
Definition: the pressure measured at the end of inspiration
peak inspiratory pressure
121
Definition: the average pressure between the mouth and alveolus, typically after an inspiratory pause
plateau pressure
122
What is the difference between PEEP and CPAP?
PEEP is in a MV patient and pressure is only during expiration
CPAP is in a spontaneously breathing patient and is pressure in both inspiration and expiration
123
What are ventilatory factors that can lead to auto-PEEP?
short expiratory times, high minute ventilation, increased airway resistance
124
Definition: The tendency of a structure to return to its original form after being stretched
elastance
125
What is the equation of motion?
Ventilator pressure + muscle pressure = elastic recoil pressure + flow resistance
126
What are the 6 basic waveforms?
rectangular
descending ramp
ascending ramp
sinusoidal
exponential rise
exponential decay
127
What are the 6 phases of the mechanical breath on a scalar
beginning of inspiration
inspiration
end of inspiration
beginning of expiration
expiration
end of expiration
128
Fill in the blank: The pressure versus time scalar shows that a _______-triggered breath started at baseline in contrast to a _______-triggered breath which has a negative deflection at the onset of the breath
ventilator (baseline)
patient (negative deflection)
129
What is the variable that determines the termination of inspiration?
cycling mechanism (can be volume, pressure, time or flow)
130
What are the three main modes of ventilation?
continuous mandatory ventilation (CMV)
intermittent mandatory ventilation (IMV)
continuous spontaneous ventilation (CSV)
131
What are the two modes of CMV and what are their triggers?
Control mode - time triggered (you set the minimum RR)
Assist control mode - patient or time triggered
132
In CMV, a ventilator assisted patient breath can be ___ or ___ triggered
pressure or flow
(the inspiratory effort of the patient leads to either a drop in pressure -2 cm H2O or in flow 2L/min)
133
What is the main benefit of SIMV?
in regular IMV, the ventilator delivers a set # of mandatory breaths and the patient can take spontaneous breaths in-between
In SIMV, the ventilator attempts to synchronize the mandatory breaths with the patient's inspiratory efforts (helps with discomfort, avoids breath stacking)
134
In which mode of MV are all breaths spontaneous?
CSV
135
In CMV volume controlled ventilation, what creates the shape of the inspiratory limb of the pressure-time scalar? (ie described what's happening)
1. Pressure rises abruptly at the beginning of inspiration when gas flow encounters resistance in the airways
2. After resistance is overcome, gas flows into the alveoli where it meet elastic resistance
3. Volume delivery ends when the set tidal volume is reached
136
In CMV pressure controlled ventilation, what creates the shape of the inspiratory limb of the pressure-time scalar?
1. The airway pressure rises rapidly to the set pressure and remains constant throughout inspiration
2. The shape of the curve is changes according to the rise time and inspiratory time
137
What is rise time?
how quickly the ventilator achieves the set target pressure (does NOT affect the inspiratory time)
138
What are causes for the expiratory limb not returning to baseline on a volume-time scalar?
air leak
bronchopleural fistula
gas trapping (auto-PEEP)
139
What are causes for the expiratory limb dropping below baseline on a volume-time scalar?
active patient exhalation
140
What is the characteristic flow pattern for volume controlled ventilation?
rectangular
141
What is the characteristic flow pattern for pressure controlled ventilation?
decelerating
142
What is the typical shape for a spontaneous unassisted breath?
sinusoidal
143
What are the benefits of pressure support ventilation (PSV)?
support a spontaneous breath
decreases work of breathing
144
How does CPAP improve oxygenation?
increases functional residual capacity
145
What loop can be used to assess lung compliance?
pressure volume loop
146
What does widening of bowing of the pressure volume loop indicate?
increased airway resistance
147
What does the lower inflection point (LIP) indicate?
the pressure at which large numbers of alveoli are recruited
148
What value on the pressure volume loop can help determine what the minimum PEEP should be for that patient?
LIP (because this is the pressure to recruit alveoli)
149
What are ways to decrease braking?
decrease the pressure in PCV
Decreased the volume in VCV
150
What does PEFR stand for?
peak expiratory flow rate
151
What portion of the flow volume loop helps to assess for changes in airway resistance?
the expiratory limb
152
What does it mean when you see a curvilinear or "scooped" out appearance of the expiratory curve on a flow-volume loop?
medium and small airway obstruction
153
What does it mean when you see a "saw tooth" sign or oscillation in the expiratory or inspiratory limb of the flow-volume loop?
increased airway secretions
154
What are two changes you can see on a pressure volume loop that indicate flow dyssynchrony?
concave portion of ascending inspiratory limb
figure 8 pattern at the top of the loop
(both of these are from active patient inspiration)
155
What does a drop in airway pressure and concave appearance of the ascension inspiratory limb on a pressure time scalar indicate?
flow dyssynchrony (flow starvation, patient needs more)
