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Respiratory > Mechanical Ventilation > Flashcards

Mechanical Ventilation Flashcards

1
Q

Following cards from CCM

A

Chapter 30, 31, 32

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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

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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 .

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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

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5
Q

What is a normal inspiratory flow rate

A

40-60L/min - this will determine insp time in volume controlled vent

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6
Q

What is ‘rise time’

A

In pressure control - the time over which pressure increases from baseline to peak

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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

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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.

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9
Q

What are the indications for MV

A

Severe hypoxaemia despite supplimentation, severe hypercapnea, unsustainable resp effort. CV collapse

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10
Q

What may be considered in brachys before weaning

A

Trach tube

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11
Q

What should ETT cuff pressures not exceed?

A
  1. I aim for 20mmHg
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12
Q

What is respiratory minute ventilation (RMV) or total minute ventilaiton equal to (Vt)

A

RR x Tv

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13
Q

What is alveolar ventilaiton

A

RMV - dead space vent

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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

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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

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16
Q

What plateau pressures are associated with pneumo in humans?

A

> 35mmHg

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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.

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18
Q

Chapter 31

A

Advanced Mechanical Ventilation

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19
Q

What are the four phases of the respiratory cycle?

A

Insp, insp pause, exp, exp pause

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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

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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

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22
Q

What may happen if the trigger variable is too sensitive

A

Equipment or patient movement may cause intiation of breath

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23
Q

What is the cycle variable?

A

the variable by which inspiration is terminated. - Usually time

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24
Q

What is controlled or assist-controlled vent

A

All machine dirven. Used for Pt with no resp drive or severe pulmonary disease

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25
Q

When is continuous spontaneous ventilation appropriate

A

For patients with adequate resp drive

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26
Q

What is intermittent manditory ventilation

A

Commonly synchronised intermittent manditory vent. SIMV - combo of manditory and synchonised breaths

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27
Q

What are some negative consequences of PEEP

A

May cause overdistension of healthy alveoli, increase dead space ventilation by reducing alveolar capillary perfusion, decreased CO due to decreased VR.

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28
Q

What are some factors of lung protective ventilation?

A

Low TV - 4-8ml/kg
higher PEEP
limiting Pplat to less than 30cmH20
permissive hypercapnea - often need more sedation

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29
Q

List causes of Asynchrony

A

Hypoxaemia, Hypercapnea, pneumo, hyoerthermia, ETT kink, inappropriate trigger, insuffient TV or insp time, poopoo, peepee, pain, too light

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30
Q

Chapter 32

A

Jet Ventilation

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31
Q

What is jet ventilation

A

Trash - hihg frequency ventilation through catheter or trans-tracheally. May allow acceptable vent when intubation not possible

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32
Q

When may jet ventilation be utilised

A

during bronchoscopy or when minimal chest movements desired

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33
Q

What are the disadvantages of jet ventilation?

A

V difficult to determine if getting adequate ventilation - ETCO2 inaccurate - need blood gas or to intermittently give normal TV breath

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34
Q

Chapter 33

A

Ventilator Waveforms

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35
Q

What is a loop vs a scalar?

A

Scalar is a single value plotted over time. Loop is two values plotted simultaneously

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36
Q

What characteristic shapes do scalars generally take?

A

Square, ascending ramp, descending ramp, sine, exponential rise and exponential decay (pg. 176 Figure 33-1)

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37
Q

When may sine waves generally be seen?

A

During modes in which patients make most efforts - Spont, CPAP

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38
Q

What do square waveforms usually mean?

A

The parameter is changes abruptly then is held at a given value (pressure in pressure control)

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39
Q

what do Ramp/Exponential wave forms mean?

A

The value is either constant or variable, with a slow rate of change (volume in volume control)

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40
Q

Which scalar gives the most information about the patients respiratory mechanics?

A

The scalar demonstrating the dependant variable

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41
Q

What does the pressure curve look like in volume control with constant flow

A

exponential rising

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42
Q

What does the pressure curve look like in pressure control

A

Square

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43
Q

What does the pressure curve look like during a volume controled insp pause?

A

develops a plataeu (lil indent)

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44
Q

What happens to pressure scalar when PEEP is applied

A

no longer reaches 0cmH20 - nor does volume

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45
Q

If there is PEEP set. What does it mean if the pressure decreases below this limit?

A

Patient effort, leak or artifact

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46
Q

What is the difference between dynamic and static complience

A

Dynamic complience includes airway and circuit resistence

47
Q

What is the dynamic and static complience equations

A

dynamic (VT/(PPeak - Peep)) static (VT/(PPlat-Peep))

48
Q

What are the determinants of mean airway pressure?

A
  1. pressure to overcome circuit
  2. pressure to deform lung and exapand alveoli
  3. pressure in expiratory flow
  4. PEEP
49
Q

What is happening when ppeak is increasing but pplat remains the same?

A

An increase in circuit or airway resistance

50
Q

What is happening if ppeak and pplat increase together?

A

worsening complience

51
Q

What flow waveforms commonly exist in volume controlled

A

square or exponential decelerating

52
Q

What are some drawbacks of constant flow volume control

A

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
Q

What information can be derived from volume scalars

A

tv and can visually see leaks or gas trapping

54
Q

What does a bowed pressure volume loop signify?

A

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
Q

What does a more horizontal PV loop mean

A

worsening static complience –> pulmonary disease

56
Q

What does beaking of the upper portion of the inspiratory PV loop mean

A

increase in pressure without a concurrent increase in volume –> alveolar overdistension

57
Q

What may a broken loop mean?

A

Open circuit

58
Q

How may flow-volume loops be helpful

A

Identifying exxcisve airway resistance - copious airway secretions and circuit leaks and dyssynchony

59
Q

kinds of trigger asynchrony exist

A

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
Q

what is flow asynchrony

A

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
Q

what is termination asynchrony?

A

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
Q

How does auto-PEEP effect patient triggering

A

Makes it more difficult for patients to trigger breaths

63
Q

CCM Chapter 34

A

Care of the Ventilator Patient

64
Q

If a patient is being ventilated due to hypoxemia - what is one reason to avoid inhalant anaesthetics

A

inhibit hypoxic pulmonary vasoconstriction

65
Q

why should prolonged propofol admin be avoided in cats

A

heinz body

66
Q

discuss when/ if cuff should be deflated and repositioned?

A

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
Q

How should the ETT be secured

A

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
Q

When should ett be changed?

A

as needed - increases vap

69
Q

Why is humidification important?

A

reduces mucous viscosity and reduces inspossation of secretions.
allows cillia function

70
Q

What are the two types of airway humidification ?

A

HME and hot water humificiation

71
Q

how often should suctioning be performed

A

It should be performed
every 4 hours or more frequently on an as-needed basis.sterile suction. pre-oxygenate.

72
Q

What is associated with an increased risk of GI bleeding in vent patients

A

increasing peep

73
Q

What are the risks and benefits of enteral nutrition on vent

A

Pros- reduced gi bleeding, reduced villus blunting, nutrition
Cons guuuuurrrrrggeeee

74
Q

What medications have been associated with ICU acquired weakness

A

NMB and steroids
The diaphragm begins to atrophy within 18hrs of ventilation (can be reduced by periods of spont)

75
Q

When should the ventilator circuit be changed ?

A

When gross contamination is noted

76
Q

CCM Chapter 35

A

Discontinuing Mechanical Ventilaiton

77
Q

What must a patient be able to do before weaning

A

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
Q

What predictors may be used to assess ‘weanability’

A

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
Q

How may a patient be weaned

A

The three main weaning techniques are SBT, pressure support
ventilation (PSV), and synchronized intermittent mandatory ventilation
(SIMV).

80
Q

Describe a spontaneous breathing trial

A

Trial in which all ventilator support is withdrawn. - occasionally CPAP is used to overcome circuit resistance.

81
Q

Should tracheostomies be performed before weaning

A

Only in upper resp disease

82
Q

is SIMV weaning associated with success in humans?

A

No

83
Q

Hopper stated prognosis

A

30% with parenchymal disease and 58% with NMJ disease

84
Q

CCM Chapter 36

A

Ventilator-Induced Lung Injury

85
Q

Define ventilator induced lung injury

A

injury to the lung caused by
mechanical ventilation in experimental models

86
Q

Define ventilator-associated lung injury

A

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
Q

In dogs how long does VILI take to develop

A

hours to days for moderate to severe
VILI to develop.

88
Q

Above what cut-off is injury extremely likely

A

VT 40ml/kg and Pressure 30cmH20 - however in already diseased lungs can take much less

89
Q

Is high volume or high pressure thought to be more injurous?

A

High volume - especially high end inspiratory volume resulting in stretch injury

90
Q

What is atelectrauma?

A

also known as shear injury/cyclic recruitment-derecruitment. –> injury due to opening and closing of alveoli caused by high volumes, surfactant loss, atelectasis.

91
Q

What is biotrauma?

A

An increase in inflammatory cytokines due to initial VILI –> this may then worsen endothelial permiability and further worsen lung injury

92
Q

What may be seen histologically due to VILI

A

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
Q

What changes may be seen with a high Fi02

A

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
Q

How can be PV loops be helpful in titration of ventilator settings

A

Lower inflection point and higher inflection point may be utilised for setting or PEEP and volume - however controversial

95
Q

CCM Chapter 37

A

Ventilator-Associated Pneumonia

96
Q

What is ventilator-associated pneumonia

A

pneumonia that arises more than 48 hours after endotracheal intubation that was not present at the time of intubation

97
Q

In humans what are the approximate risks of developing VAP?

A

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
Q

How is the ETT asociated with VAP

A

microaspiration past the cuff and biofilm development represent 2 pathologuc mechanisms.

99
Q

What are sources of exogenous contamination?

A

contaminated respiratory equipment, the environment, or
healthcare provider’s hands.

100
Q

what are sources of endogenous contamination

A

oral, gastric

101
Q

how is vap diagnosed?

A

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
Q

What are non-pharmacoloigical methods for VAP reduction

A

Hand hygiene, protocol based weaning that may mean patietns are weaned earlier, trachs shown no difference

103
Q

What are some pharmacologic strategies for reducing VAP

A

Oral decontamination with chlorhex, oral topical abs, avoid use of PPIs

104
Q

When should treatment for VAP begin

A

Immediately once suspected

105
Q

Advanced Monitoring and Procedures

A

chapter 29 - High-frequency ventilation

106
Q

WHat is the resonant frequency of the respiraotry system?

A

is the natural frequency of the system at which
vibrations will occur with the least amount of energy being applied - more energy efficient.

107
Q

What is the definition of high frequency ventilation

A

any technique that applies a higher resp rate - usually 10 times what is normal for the species

108
Q

What is high frequ jet vent

A

High-frequency jet ventilation (HFJV) provides ventilation
at rates of 60–400 breaths per minute in people.
Inspiration is active; expiration is passive

109
Q

What is Highfrequency
oscillometric ventilation (HFOV)

A

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
Q

How is HFJV applied

A

With a jet ventilator - insp time usually 20 milisec AND a conventional vent applying sigh breaths 2-10/min

111
Q

How is HFOV applied?

A

provided
with a piston and diaphragm, which makes both inspiration
and expiration active.- no venilator needed. I:E set to 1:2

112
Q

When may high frequ vent be indicated?

A

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
Q

What are the goals of high frequency vent

A

maintenance
of optimal lung volume and adequate blood gases

Respiratory (3 decks)

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