Mechanical Ventilation Flashcards
1
Q
Following cards from CCM
A
Chapter 30, 31, 32
2
Q
What is compliance?
A
A measure of the distensibility of the lung. The change in lung volume for a given change in pressure.
Decreases with pulmonary disease obvs
3
Q
What types of ventilator breaths exist?
A
Spontaneous - patient determines rate and TV.
Assisted - patient determines rate, machine determines TV.
Controlled - Machine both .
4
Q
What does Hopper say normal TV is
A
10-15ml/kg but evidence is lacking. Most says spont breath in mammals is 6-7ml/kg. Including humans.
https://www.minervamedica.it/en/getfreepdf/MVFjRGRhbEowYmI3SCtjTVYxV2Ywd1pFdWFPbTAvT24rRXlHN0NFTzlpWmErb0dkYWplYWduQW5veXdQZlhIOA%253D%253D/R02Y2014N11A1149.pdf
https://pubmed.ncbi.nlm.nih.gov/26031349/
https://www.frontiersin.org/articles/10.3389/fvets.2022.842528/full
5
Q
What is a normal inspiratory flow rate
A
40-60L/min - this will determine insp time in volume controlled vent
6
Q
What is ‘rise time’
A
In pressure control - the time over which pressure increases from baseline to peak
7
Q
What is the trigger variable?
A
The variable the ventilator uses know when to give a breath. In animals with no resp drive is often time. If animal is initiating breath may be change in pressure or change in flow
8
Q
What is peep
A
Positive end-expiratory pressure. holds pressure in alveoli following exp. increase oxygenation by recruiting collapsed alveoli, preventing cyclic collapse and atelectotrauma.
9
Q
What are the indications for MV
A
Severe hypoxaemia despite supplimentation, severe hypercapnea, unsustainable resp effort. CV collapse
10
Q
What may be considered in brachys before weaning
A
Trach tube
11
Q
What should ETT cuff pressures not exceed?
A
- I aim for 20mmHg
12
Q
What is respiratory minute ventilation (RMV) or total minute ventilaiton equal to (Vt)
A
RR x Tv
13
Q
What is alveolar ventilaiton
A
RMV - dead space vent
14
Q
Regarding oxygenation what are the first things that should be titrated down
A
FiO2 below 60% then Peep and Tv/Ppeak to reduce risk of ventilator induced lung injury
15
Q
What complications may arise as the result of MV?
A
CV collapse, hypotension, hypothermia, pneumothorax, ventilator induced lung injury, VAP, corneal ulceration, AKI, fluid overload
16
Q
What plateau pressures are associated with pneumo in humans?
A
> 35mmHg
17
Q
What will be seen if pneumothorax occurs on the vent?
A
Acute decline in O2, evelvation in CO2, decreased chest wall movement, marked increase in pressures, asynchrony.
18
Q
Chapter 31
A
Advanced Mechanical Ventilation
19
Q
What are the four phases of the respiratory cycle?
A
Insp, insp pause, exp, exp pause
20
Q
What are the three types of breath
A
Spont - all patient
Assisted - intiated by patient, Tv or pressure support by machine
manditory/controlled - all machine
21
Q
On page 167 without looking at the image description identify the ventilation mode based on the waveforms
A
A is pressure B is volume
22
Q
What may happen if the trigger variable is too sensitive
A
Equipment or patient movement may cause intiation of breath
23
Q
What is the cycle variable?
A
the variable by which inspiration is terminated. - Usually time
24
Q
What is controlled or assist-controlled vent
A
All machine dirven. Used for Pt with no resp drive or severe pulmonary disease
25
When is continuous spontaneous ventilation appropriate
For patients with adequate resp drive
26
What is intermittent manditory ventilation
Commonly synchronised intermittent manditory vent. SIMV - combo of manditory and synchonised breaths
27
What are some negative consequences of PEEP
May cause overdistension of healthy alveoli, increase dead space ventilation by reducing alveolar capillary perfusion, decreased CO due to decreased VR.
28
What are some factors of lung protective ventilation?
Low TV - 4-8ml/kg
higher PEEP
limiting Pplat to less than 30cmH20
permissive hypercapnea - often need more sedation
29
List causes of Asynchrony
Hypoxaemia, Hypercapnea, pneumo, hyoerthermia, ETT kink, inappropriate trigger, insuffient TV or insp time, poopoo, peepee, pain, too light
30
Chapter 32
Jet Ventilation
31
What is jet ventilation
Trash - hihg frequency ventilation through catheter or trans-tracheally. May allow acceptable vent when intubation not possible
32
When may jet ventilation be utilised
during bronchoscopy or when minimal chest movements desired
33
What are the disadvantages of jet ventilation?
V difficult to determine if getting adequate ventilation - ETCO2 inaccurate - need blood gas or to intermittently give normal TV breath
34
Chapter 33
Ventilator Waveforms
35
What is a loop vs a scalar?
Scalar is a single value plotted over time. Loop is two values plotted simultaneously
36
What characteristic shapes do scalars generally take?
Square, ascending ramp, descending ramp, sine, exponential rise and exponential decay (pg. 176 Figure 33-1)
37
When may sine waves generally be seen?
During modes in which patients make most efforts - Spont, CPAP
38
What do square waveforms usually mean?
The parameter is changes abruptly then is held at a given value (pressure in pressure control)
39
what do Ramp/Exponential wave forms mean?
The value is either constant or variable, with a slow rate of change (volume in volume control)
40
Which scalar gives the most information about the patients respiratory mechanics?
The scalar demonstrating the dependant variable
41
What does the pressure curve look like in volume control with constant flow
exponential rising
42
What does the pressure curve look like in pressure control
Square
43
What does the pressure curve look like during a volume controled insp pause?
develops a plataeu (lil indent)
44
What happens to pressure scalar when PEEP is applied
no longer reaches 0cmH20 - nor does volume
45
If there is PEEP set. What does it mean if the pressure decreases below this limit?
Patient effort, leak or artifact
46
What is the difference between dynamic and static complience
Dynamic complience includes airway and circuit resistence
47
What is the dynamic and static complience equations
dynamic (VT/(PPeak - Peep)) static (VT/(PPlat-Peep))
48
What are the determinants of mean airway pressure?
1. pressure to overcome circuit
2. pressure to deform lung and exapand alveoli
3. pressure in expiratory flow
4. PEEP
49
What is happening when ppeak is increasing but pplat remains the same?
An increase in circuit or airway resistance
50
What is happening if ppeak and pplat increase together?
worsening complience
51
What flow waveforms commonly exist in volume controlled
square or exponential decelerating
52
What are some drawbacks of constant flow volume control
usually results in a higher ppeak than same tv with exponential decay flow, and can't customise inspiratory time - however constant flow allows for calc of resp mechanics
53
What information can be derived from volume scalars
tv and can visually see leaks or gas trapping
54
What does a bowed pressure volume loop signify?
More pressue is required to reach a given volume due to an increase in dymanic complience --> should prompt clinician to invesitgated blocked or kinked ETT, airway succtioning or bronchodilator administration.
55
What does a more horizontal PV loop mean
worsening static complience --> pulmonary disease
56
What does beaking of the upper portion of the inspiratory PV loop mean
increase in pressure without a concurrent increase in volume --> alveolar overdistension
57
What may a broken loop mean?
Open circuit
58
How may flow-volume loops be helpful
Identifying exxcisve airway resistance - copious airway secretions and circuit leaks and dyssynchony
59
kinds of trigger asynchrony exist
ineffective triggering (tirgger not sensitive enough) - often use flow scalar to see, double triggering (patient triggering a breath on top of an manditory breath) - high ventilatory depand, low tv or short I time or auto-triggering (too sensitive)
60
what is flow asynchrony
ventilator supply of fresh gas to
the inspiratory circuit that is either too fast or too slow for the individual
patient. - can be visualised in either pressure or volume control
61
what is termination asynchrony?
termination or cycling asynchronyhas two types - inspiration being
terminated too early (premature cycling still trying to breath in when insp terminated) or too late
(delayed cycling trying to breath out when still insp
62
How does auto-PEEP effect patient triggering
Makes it more difficult for patients to trigger breaths
63
CCM Chapter 34
Care of the Ventilator Patient
64
If a patient is being ventilated due to hypoxemia - what is one reason to avoid inhalant anaesthetics
inhibit hypoxic pulmonary vasoconstriction
65
why should prolonged propofol admin be avoided in cats
heinz body
66
discuss when/ if cuff should be deflated and repositioned?
To help prevent tracheal necrosis, it has been suggested to deflate
the cuff and reposition it every 4 hours in veterinary medicine.4
However, to help prevent VAP, the American Thoracic Society recommends
that cuff pressure be maintained at more than 20 cm H2O.12
The risk of tracheal necrosis versus the risk of VAP should be weighed
in each individual patient.
if can measure cuff pressure they recommend not deflating
67
How should the ETT be secured
a nonporous material such
as plastic intravenous tubing. Gauze exposed to oral secretions provides
a growth medium for bacteria.
Retired every 4 hours to prevent damage to the lips. Should be replaced every 24 hours to help prevent biofilm
accumulation.
68
When should ett be changed?
as needed - increases vap
69
Why is humidification important?
reduces mucous viscosity and reduces inspossation of secretions.
allows cillia function
70
What are the two types of airway humidification ?
HME and hot water humificiation
71
how often should suctioning be performed
It should be performed
every 4 hours or more frequently on an as-needed basis.sterile suction. pre-oxygenate.
72
What is associated with an increased risk of GI bleeding in vent patients
increasing peep
73
What are the risks and benefits of enteral nutrition on vent
Pros- reduced gi bleeding, reduced villus blunting, nutrition
Cons guuuuurrrrrggeeee
74
What medications have been associated with ICU acquired weakness
NMB and steroids
The diaphragm begins to atrophy within 18hrs of ventilation (can be reduced by periods of spont)
75
When should the ventilator circuit be changed ?
When gross contamination is noted
76
CCM Chapter 35
Discontinuing Mechanical Ventilaiton
77
What must a patient be able to do before weaning
adequate gas exchange without the
support of aggressive ventilator settings, an appropriate ventilatory
drive, and recovery from significant systemic disease such as cardiovascular
instability or organ failure
78
What predictors may be used to assess 'weanability'
rapid shallow breathing index, dead space vent, spont breathing trials - HOWEVER
None of the proposed weaning predictors have been shown to
perform adequately enough to be used alone for clinical decision
making.
79
How may a patient be weaned
The three main weaning techniques are SBT, pressure support
ventilation (PSV), and synchronized intermittent mandatory ventilation
(SIMV).
80
Describe a spontaneous breathing trial
Trial in which all ventilator support is withdrawn. - occasionally CPAP is used to overcome circuit resistance.
81
Should tracheostomies be performed before weaning
Only in upper resp disease
82
is SIMV weaning associated with success in humans?
No
83
Hopper stated prognosis
30% with parenchymal disease and 58% with NMJ disease
84
CCM Chapter 36
Ventilator-Induced Lung Injury
85
Define ventilator induced lung injury
injury to the lung caused by
mechanical ventilation in experimental models
86
Define ventilator-associated lung injury
worsening of pulmonary function,
or presence of lesions similar to acute respiratory distress syndrome,
in clinical patients that is thought to be associated with the
use of mechanical ventilation, with or without underlying lung
disease
87
In dogs how long does VILI take to develop
hours to days for moderate to severe
VILI to develop.
88
Above what cut-off is injury extremely likely
VT 40ml/kg and Pressure 30cmH20 - however in already diseased lungs can take much less
89
Is high volume or high pressure thought to be more injurous?
High volume - especially high end inspiratory volume resulting in stretch injury
90
What is atelectrauma?
also known as shear injury/cyclic recruitment-derecruitment. --> injury due to opening and closing of alveoli caused by high volumes, surfactant loss, atelectasis.
91
What is biotrauma?
An increase in inflammatory cytokines due to initial VILI --> this may then worsen endothelial permiability and further worsen lung injury
92
What may be seen histologically due to VILI
decreased integrity of small airway epithelial cells, destruction of type 1 alveolar epithelial cells, alveolar and airway flooding, hyaline membrane formation, interstitial edema, and infiltration of inflammatory cells.
93
What changes may be seen with a high Fi02
Absorption atelectasis.
Production of reactive oxygen and nitrogen species and has been shown to cause pathologic change similar to ARDS and VILI, including interstitial edema, hyaline membrane formation, damage to the alveolar membrane, altered mucociliary function, and fibroproliferation
94
How can be PV loops be helpful in titration of ventilator settings
Lower inflection point and higher inflection point may be utilised for setting or PEEP and volume - however controversial
95
CCM Chapter 37
Ventilator-Associated Pneumonia
96
What is ventilator-associated pneumonia
pneumonia that arises more than 48 hours after endotracheal intubation that was not present at the time of intubation
97
In humans what are the approximate risks of developing VAP?
8-28%, 0-6 per 1000 ventilator days, 3.3% for the first 5 days then 2.3% from day 6-10 then 1.3% thereafter
98
How is the ETT asociated with VAP
microaspiration past the cuff and biofilm development represent 2 pathologuc mechanisms.
99
What are sources of exogenous contamination?
contaminated respiratory equipment, the environment, or
healthcare provider’s hands.
100
what are sources of endogenous contamination
oral, gastric
101
how is vap diagnosed?
many different criteria!
The clinical diagnosis of VAP in an individual patient usually
requires two of the following three criteria: fever, either leukocytosis
or leukopenia, and purulent airway secretions
rads often difficult due to pre-existing airway disease
airway sampling.
102
What are non-pharmacoloigical methods for VAP reduction
Hand hygiene, protocol based weaning that may mean patietns are weaned earlier, trachs shown no difference
103
What are some pharmacologic strategies for reducing VAP
Oral decontamination with chlorhex, oral topical abs, avoid use of PPIs
104
When should treatment for VAP begin
Immediately once suspected
105
Advanced Monitoring and Procedures
chapter 29 - High-frequency ventilation
106
WHat is the resonant frequency of the respiraotry system?
is the natural frequency of the system at which
vibrations will occur with the least amount of energy being applied - more energy efficient.
107
What is the definition of high frequency ventilation
any technique that applies a higher resp rate - usually 10 times what is normal for the species
108
What is high frequ jet vent
High-frequency jet ventilation (HFJV) provides ventilation
at rates of 60–400 breaths per minute in people.
Inspiration is active; expiration is passive
109
What is Highfrequency
oscillometric ventilation (HFOV)
provides ventilation at rates >400 breaths/min. In this form, both inspiration and expiration are active, and the gas flow is sinusoidal rather than the triangular flow seen with HFJV
110
How is HFJV applied
With a jet ventilator - insp time usually 20 milisec AND a conventional vent applying sigh breaths 2-10/min
111
How is HFOV applied?
provided
with a piston and diaphragm, which makes both inspiration
and expiration active.- no venilator needed. I:E set to 1:2
112
When may high frequ vent be indicated?
The use of HFV is advised when
high respiratory rates are required because CVs are not responsive at such rates, and air trapping (auto-PEEP) is a potential concern due to breath stacking.
May also reduce biotrauama from cyclic opening and closing
or interventional procedures
113
What are the goals of high frequency vent
maintenance
of optimal lung volume and adequate blood gases
