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ICU > Ventilation > Flashcards

Ventilation Flashcards

1
Q

Ways of triggering ventilation

A

Breaths may be triggered by the patient (usually pressure or flow) or

ventilator (time)

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2
Q

FiO2 range

A

The FiO2 range is from 0.21 (room air) to 1 (100% O2)

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3
Q

What is PEEP ? Usual level starting

A

The amount of pressure in the breathing circuit at the end of exhalation
5-10 cm H2O

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4
Q

Why start PEEP low

A

prevent end-expiratory alveolar collapse

->reducing atelectasis and improving gas exchange.

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5
Q

What is spontaneous mode of ventilation

A

Only delivers support to the patient’s breathing if
the patient has some respiratory effort.

The patient starts the breath and the ventilator then
provides additional positive pressure during inspiration in order to reduce the work of breathing and
improve gas exchange

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6
Q

What is controlled mode ventilation

A

delivers ventilation regardless of the patient’s

respiratory effort. This can be volume or pressure controlled.

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7
Q

What is volume-controlled mode ventilation?

What does airway pressure depend on?

A

Refers to modes of ventilation where the volume of the breath is set (tidal volume is set). The number of breaths per
minute (bpm) is also set

Eg a tidal volume of 500ml at a rate of 14 bpm. The ventilator in this example is
set to deliver a minute volume of 500 x 14 = 7 litres.

lung and chest wall compliance
(and may change from breath to breath)

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8
Q

What is pressure-controlled mode ventilation?

what is affected by the lung and chest wall compliance?

A

the pressure of the breath is set, e.g. we set the ventilator to
deliver a breath pressure of 30cm H2O. The number of bpm is also set.

Eg. set the breath pressure at 30cm H2O to be delivered at a rate of 14 bpm.

The tidal volume in this mode of ventilation will depend on the lung and chest wall compliance
and may change from breath to breath.

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9
Q

What is I:E time ? normal value ? When might we need an increased ratio?

A

The ratio of inspiratory time: expiratory time

the expiratory time is about twice as long as the inspiratory time.
This gives an I:E ratio of 1:2

in asthmatics to allow prolonged time for expiration, and prevent breath stacking. They might require an I:E ratio of 1:3 or 1:4

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10
Q

What is an inverse I:E ratio? when is it used ?

A

I: E ratio is higher than 1:1, and is typically used to ventilate non-compliant lungs

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11
Q

3 things to trigger expiration on ventilator

A

flow (e.g. pressure support ventilation),

time (pressurecontrolled ventilation),

volume (volume-controlled ventilation) is reached.

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12
Q

What two things do you monitor to protect lungs on ventilators

A

peak airway pressure, platau airway pressure

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13
Q

What is peak aairway pressure ? What does it represent

A

(Peak Paw) refers to the highest airway pressures

Peak Paw is normally taken to represent pressure in the major airways

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14
Q

What is platau pressure ? what does it represent ?

A

(Plateau Paw) is that which occurs during the plateau phase of volume controlled ventilation

plateau pressure
represents pressure at the alveolar level.

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15
Q

What is n Synchronized Intermittent Mandatory Ventilation

A

To improve patient ventilator interaction, SIMV incorporates a synchronization window in mid-late expiration during which spontaneous effort is augmented and turned into a mandatory breath.

In effect, the next mandatory breath is delivered early to coincide with the patient’s spontaneous respiratory effort.

Spontaneous breaths outside this synchronization window may be unsupported or pressure supported (SIMV+PS).

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16
Q

3 types of breath in (S)IMV + PS

A

Mandatory breaths: time triggered volume or time cycled.

Supported breaths: patient triggered, flow cycled.

Synchronised breaths: patient triggered volume or time cycled.

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17
Q

Initial Fio2 for intubation

A

100%

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18
Q

What tidal volume initially set for ventilation? iN 80Kg

A

6ml/kg/IBW

Approx 400ml

19
Q

Initial starting RR in ventilation

A

15

20
Q

Initial I:E ratio

A

1:2

21
Q

Initially controlled or spontaneous ventilation

A

controlled as likely anaesthetised/paralysed

22
Q

Main 3 complications of ventilation

A

Ventilator-induced lung injury
haemodynamic instability
ventilator-associated pneumonia

23
Q

Mechanism of Ventilator-induced lung injury

A 
Combination of barotrauma (injury due to pressure)
and volutrauma (due to volume) which causes alveolar strain

Also, get atelectrauma due to excessive opening and closing of alveoli

24
Q

How to prevent ventilator induced lung injury

A

permissive hypercapnia/hypoxia
In ARDS - reduce plateau pressure to <30cm h20
- tidal volume no more than 6ml/kg
-aim for PEEP which prevents end alveolar closure but doesn’t give cause alveolar strain

25
Q

Mechanism of ventilator induced haemodynamic instability? Population more susceptible?

A

increased pressure -> reduced preload ->reduced CO

Pt with reduced hypovolemia
Reduced lung compliance -> less pressure transmitted to vessels

26
Q

Diagnostic criteria ARDS

A

Acute onset

Bilateral infiltrates on chest x-ray

Respiratory failure is not explained by cardiac failure or fluid overload

known risk factor

27
Q

Mild vs moderate vs severe ards

A

Mild PaO2/Fio2 = 200-300mmHg
Moderate 100-200
severe <100

28
Q

Management of ARDS is treat the cause. What methods in interim?

A

Increase FiO2
protective lung ventilation
increase mean airway pressure
permissive hypoxia / hypercapnia

29
Q

Name 3 ways to increase mean airway pressure

A

Increase PEEP
Increase inspiratory pressure
Increase inspiratory time

30
Q

4 types of ventilator-associated lung injury - how to prevent

A
  • Barotrauma: Due to high airway pressures, especially plateau Paw over 30 CmH2O.
  • Volutrauma: Due to high tidal volumes (more than 6ml/kg in patients with ARDS).
  • Atelactrauma: Due to cyclical collapse (atelactasis) and opening of the alveoli.
  • Prevent using appropriate level of PEEP.

Oxygen toxicity: due to prolonged exposure to high FiO2. Unknwon mechanism - thought to be due to free radical production.

31
Q

Why do ventilators cause haemodynamic instability

A
  • Reduces preload -> reduces CO
  • Hypovolaemic patients very sensitive
  • reduced lung compliance can tolerate higher intrathoracic pressures
32
Q

Why does PEEP help

A
  • increases functional residual capacity (FRC)
  • recruites collapsed alveoli
  • reduces shunt
33
Q

What is IPPV?
volume / pressure controlled?
Does it require spontaneous effort?
is it synchronised?

A

Intermittent positive pressure ventilation.

  • Can be volume or pressure controlled, is a controlled mode of ventilation
  • (does not require any spontaneous respiratory effort from the patient), and is
  • not synchronised with patient’s respiratory effort.
34
Q

Most common ventilator mode?
volume / pressure controlled?
Does it require spontaneous effort?
is it synchronised?

A

SIMV = Synchronised Intermittent mandatory ventilation.
- Can be volume or pressure controlled.
- Is a controlled mode of ventilation (does not require any spontaneous respiratory effort from the patient),
Is synchronised

SIMV and PCV are almost always combined with PS to allow the support of any spontaneous breaths that the patient takes on top of the mandatory breaths delivered.

35
Q

What is PCV / BiPAP
volume / pressure controlled?
Does it require spontaneous effort?
is it synchronised?

A

Pressure controlled ventilation and Bilevel positive airway pressure.

  • Are pressure controlled modes of ventilation.
  • They are controlled modes of ventilation, but allow synchronisation if the patient takes spontaneous breaths.
  • The two modes are slightly different in the way synchronisation occurs.
36
Q

What is pressure support also called? What is it?

A

assisted spontaneous breathing).

  • Is a spontaneous mode of ventilation that is pressure controlled.
  • It is fully synchronised with the patient’s breath.
37
Q

Main categories of ventilator complications

A

VILI

Haemodynamic instability

Ventilator associated pneumonia

Pneumothorax

38
Q

Calculate compliance in ventilation

A

Compliance = change in volume / Change in pressure

volume = pressure x compliance

39
Q

What is PRVC ?
Means?
What happens

A

Pressure regulated volume control
Operates like pressure control but ensures a set volume is delivered
Pressure control but with a set TARGET VOLUME

Ventilator automatically adjusts the pressure by small amounts to ensure target volume is met

40
Q

What is APRV?

what happens ?
What is it good for ?
Issue?

A

Airway pressure release ventilation

Ventilator holds prolonged periods of high pressure with short periods of low pressure
(Think like CPAP with lots of high pressure with periods of release)

Really good for recruiting collapsed alveoli as mean pressure is really high

Pts able to take spontaneous breaths as in CPAP

Issue as short low pressure time ->CO2 retention

41
Q

Extra settings in Airway pressure release ventilation (APRV)

A

Phigh, Plow
(high pressure, low pressure)

T-high, T-low
(time at high pressure, time at low pressure)

42
Q

What is HFOV

A

High frequency oscillatory ventilation
(usually seen in NICU - Neonates)

Essentially very high respiratory rate
4-7Hz (240-420 Breaths per min)
Very low Tidal volume - eg 1-2ml

Increases Mean airway pressure

43
Q

High CO2 on vent. What settings can you change?

A

Usually due to poor gas exchange
Need to increase minute volume
Either- RR or Tidal volume
(Usually RR)

44
Q

Low O2 on vent what setting can you change

A

Usually due to poor alveolar filling of O2
-> increase mean alveolar pressure
Usually increase PEEP
Or IE ratio

ICU (8 decks)

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