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Applied Clinical Veterinary Nursing > Ventilators and Ventilation > Flashcards

Ventilators and Ventilation Flashcards

1
Q

What physical factors can affect spontaneous ventilation?

A

Physiological/anatomical
Airway obstruction
Stenotic nares
Excess tissue around airway
Hypoplastic trachea
Obesity (pressure on diaphragm)
Restriction e.g. effusions

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2
Q

What external factors can affect spontaneous ventilation?

A

ET tube size?
Restriction e.g. sandbags/surgeon’s hands

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3
Q

What are the two indications for assisted ventilation?

A

Reduced drive to ventilate
Inability to ventilate/do so effectively

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4
Q

Why might patients have a reduced ventilatory drive?

A

Anaesthetic drugs
CNS disease (raised ICP/encephalopathy)
Hypothermia

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5
Q

Why might patients be unable to ventilate themselves?

A

Open thoracic cavity
Muscle failure (NMBs/myasthenia gravis)
Nerve failure (intercostal/diaphragmatic)
External factors affecting lung inflation

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6
Q

What can we monitor to indicate the need for manual ventilation?

A

Ventilatory pattern
Tidal/minute volume - spirometry
Blood gases
ETCO2/SpO2

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7
Q

What are the pros of manual ventilation (i.e. circuit/ambu-bag)?

A

Easy to perform
Cheap/does not need much equipment

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8
Q

What are the cons of manual ventilation?

A

Dependent on operator
Poor control of airway pressures
Each breath may be different
Operator fatigue
Boring / time-consuming!

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9
Q

What are the pros of mechanical ventilation?

A

Allows hands-free anaesthetic
Ensures appropriate volumes of gas are administered

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10
Q

What are the cons of mechanical ventilation?

A

Not always available
Expensive - initial investment
Requires skill

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11
Q

What cardiovascular side effects of IPPV can we see?

A

Decreased CO (due to increased pressure within thorax)
Decreased venous return
Reduced stroke volume
Reduced pre-load
Reduced BP

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12
Q

Which organs can struggle with perfusion during IPPV?

A

Liver
Kidneys

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13
Q

Describe the renin-angiotensin-aldosterone system side effects during IPPV.

A

Sympathetic NS notices reduced BP
Triggers increased HR
Increased HR = increased cardiac workload
Increased cardiac workloads = increased O2 requirements
RAA system kick in = vasoconstriction/urine retention/ADH release

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14
Q

What other side effects can we see from IPPV?

A

Barotrauma/volutrauma
Oxygen toxicity (ideally 100% O2 for less than 6hrs)

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15
Q

How can we monitor the efficacy of ventilation?

A

Observation
Auscultation
Capnography
Arterial blood gases

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16
Q

How can we use observation to monitor efficacy of ventilation?

A

Look at thoracic movements - anything compromising?
Look at abdominal movements

17
Q

How can we use auscultation to monitor efficacy of ventilation?

A

Sounds/air entering both lungs at all areas?
If not - bronchial intubation? Atelectasis? Neoplasia? Fluid/material in pleural space?

18
Q

How can we use capnography to monitor efficacy of ventilation?

A

Very useful - but does not give info on tidal volume
If high, increase minute volume
If low, may reduce minute volume

19
Q

How can we use arterial blood gases to monitor efficacy of ventilation?

A

PaO2 = partial pressure of O2 in arterial circulation
Much better indicator than SpO2
PaCO2 can compare with ETCO2 - but may be slight difference

20
Q

Define ventilator.

A

A machine designed to provide mechanical ventilation to a patient, by moving air into and out of the lungs

21
Q

Why might we need to use a ventilator?

A

Apnoeic/poorly ventilated patient
NMBs
Thoracotomy - with resp/non-resp disease
Diaphragmatic rupture

22
Q

What settings can we adjust on a ventilator?

A

Frequency of breaths
Tidal/minute volume
I:E ratio
Inspiratory flow rate
PIP (Peak Inspiratory Pressure - highest pressure measured during resp cycle)
PEEP (Positive End Pressure Ventilation - pressure applied by ventilator at end of each breath to ensure alveoli are not prone to collapse)

23
Q

Define cycling and the four variables used to determine this.

A

Change from inspiration to expiration
Variables determine when and how ventilator moves from inspiration to expiration - pressure, volume, time, flow

24
Q

Describe pressure-controlled ventilation.

A

Ventilator maintains set airway pressure for set inspiratory time
User can pre-set a max. pressure and ventilator will deliver volume of gas until this pressure is reached
Inspiratory flow of gas is delivered until trigger pressure is reached - this causes inspiratory cut off and begins expiratory cycle

25
Q

When can over-inflation occur with pressure-controlled ventilation?

A

If lung compliance changes e.g. open chest, then a much larger volume of gas will be delivered before trigger pressure is reached

26
Q

Describe volume-controlled ventilation.

A

Set tidal volume, pressure limit, rate, inspiratory time/I:E ratio
Start - check expansion (TV) and ETCO2 (ventilation)

27
Q

How can volume-controlled ventilation prevent over-inflation?

A

Does not rely on airway compliance change - the set volume will be given if chest is open or closed
May have a pressure cut-off

28
Q

Describe time-controlled ventilation.

A

Ventilator breath switches from inspiratory to expiratory after a set time is reached
Set resp rate and inspiratory time/I:E ratio

29
Q

Describe flow-controlled ventilation.

A

Ventilatory delivers a set flow until total volume has been delivered
Useful in paediatrics

30
Q

Define assist control mode.

A

Breath is initiated by patient

31
Q

Define control mode.

A

Breath is controlled by machine

32
Q

What is the typical inspiratory:expiratory ratio?

A

1:2 (i.e. expiratory time is usually twice the inspiratory time)

33
Q

What are the three types of bag squeezer ventilators?

A

Ascending bellow
Descending bellow
Horizontal bellow

34
Q

Describe how bag squeezer ventilators work.

A

Set volume and I:E ratio
Pressure gauge
Set tidal volume, then set inspiratory time
This will work out resp rate

35
Q

Describe mechanical thumb ventilators.

A

Imagine thumb over a T-piece
Used in small animal anaesthesia i.e. rodent/lab

36
Q

Describe intermittent blower ventilators.

A

Takes driving gas and divides it into smaller volumes
Uses that to push gas into the patient

37
Q

Describe minute volume divider ventilators.

A

Collect continuous flow of gas into reservoir
Delivery to patient under positive pressure
FGF = intended minute volume, divided up into required breaths/min
Expensive in terms of FGF

38
Q

What patient care must we provide during long periods of ventilation?

A

Oral/eye care
Humidification of gases
ET tube care - suction, deflate cuff and reposition
Monitoring efficacy of ventilation
Periodic ‘sigh’?
Physiotherapy - limb mobilisation
Turning patient

39
Q
A

Applied Clinical Veterinary Nursing (40 decks)

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