Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Basic Course > Basic Mechanical Ventilation > Flashcards

Basic Mechanical Ventilation Flashcards

1
Q

what determines the pressure required to make gas flow down a tube

A

the flow rate x the resistance in the tubing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what determines the pressure required to inflate a balloon?

A

the volume to which the balloon is inflated divided by the compliance of the balloon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what determines the pressure required to make air flow down a tube AND inflate a balloon (this is the pressure required to inflate the lung)

A

this is AKA the inflation pressure

inflation pressure = (flow x resistance) + volume/compliance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is the airway pressure

A

Paw is the inflation pressure + the pressure in the balloon at the end of expiration (PEEP)

Paw = (flow x resistance) + (volume/compliance) + PEEP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is alveolar pressure

A

(volume/compliance) + PEEP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is flow

A

volume/time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

ways to improve oxygen in

A
  • increase FiO2
  • reduce shunting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

ways to reduce shunting

A

increase PEEP or increase inspiratory time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

ways to blow off CO2

A

increase resp rate or tidal volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does PEEP reduce shunting

A

Opens alveoli and keeps them open

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

why can inspiratory time be set as a function of flow

A

because flow is volume/time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

name 3 respiratory complications of mechanical ventilation

A

nosocomial pneumonia
ventilator associated lung injury
gas trapping

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

three causes of ventilator associated lung injury

A

high pressures (barotrauma)
high volumes (volutrauma)
shear injury

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

difference between volutrauma and barotrauma

A

barotrauma is gas leak injury such as pneumothorax, pneumomediastium, pneumoperitoneum etc

volutrauma is a histological appearance similar to ARDS - complication of lungs being repeatedly extended to excessive volumes, its an acute lung injury

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is shear injury

A

from repetitive opening and closing of alveoli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

when does gas trapping occur

A

when there’s insufficient time for alveoli to empty before the next breath

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

4 predisposing factors in gas trapping

A
  • asthma or copd
  • long inspiratory time (short expiratory time
  • high respiratory rate (short expiratory time)
  • large tidal volumes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how can you measure the degree of gas trapping

A
  • gas trapping increases PEEP
  • because this increase is not because of the extrinsic PEEP (that you set on the vent) it is part of intrinsic PEEP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is intrinsic PEEP

A

its either described as PEEPtotal if this value is greater than PEEPe
or
PEEPi = PEEPtotal - PEEPe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How can you measure PEEPtotal

A

expiratory pause hold control on the vent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

complications of gas trapping

A
  • barotrauma
  • cardiovascular compromise –> PEA cardiac arrest in extreme cases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

effect on preload of ventilation

A

reduces preload:
- normally venous return is enhanced by negative intrathoracic pressures during inspiration
- during positive pressure ventilation venous return is impeded and preload is reduced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

features of ventilation that would decrease preload

A

high inspiratory pressure
prolonged inspiratory time
higher PEEP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

effects of ventilation on afterload

A
  • afterload is dependent on transmural pressure of the left ventricle in that as Ptm goes up so does afterload
  • Ptm = the intracavity pressure (Pic) - the pleural pressure (Ppl)
  • therefore ventilating someone with increasingly high pressures will lead to a reduction in afterload
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

overall effect of ventilation on cardiac output

A
  • ventilation decreases afterload and decreases preload
  • both of these have differing effects on cardiac output
  • overall effect of positive pressure ventilation on cardiac output depends on the contractility of the ventrical
  • normal contractility –> decreased cardiac output
  • decreased contractility –> increased cardiac output
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what is volume pre-set assist control ventilation

A
  • AKA VC-A/C on dragers
  • operator sets tidal volume, I:E and minimum ventilatory rate
  • both patient and ventilator can initiate breaths
  • if the pt does not initiate breaths frequently enought then the ventilator will initiate for her
  • characteristics of the breath are the same whether pt initiates or the vent initiates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

advantages of volume pre-set assist control ventilation

A

-simple to set up
- guaranteed minimum minute ventilation
- rests muscles of respiration if set properly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Disadvantages of volume pre-set assist control ventilation

A
  • not always synchronised with patient’s breathing
  • pt may lead the ventilator
  • inappropriate triggoring (e.g. hiccups) may lead to excessive minute ventilation
  • can’t directly control pressures
  • often requires sedation due to discomfort due to dyssynchrony
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what is pressure pre-set assist control ventilation

A
  • aka pressure control
  • inspiratory pressure is set instead of tidal volume
  • because of a constant pressure there is a high initial flow that falls to zero by the end of inspiration
  • reducing inspiratory time may decrease tidal volume if there is still inspiratory flow at the end of inspiration
  • extending inspiratory time beyond the point when inspiratory flow falls to zero does not increase the tidal volume
  • can’t control the pressure and therefore a fall in compliance could lead to barotrauma
  • equally an increase in airway resistance could lead to a higher airway pressure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

advantages of pressure pre-set assist control ventilation

A
  • simple to set
  • avoids high inspiratory pressures
  • rests muscles of respiration
  • decelerating flow pattern gives better oxygenation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

disadvantages of pressure pre-set assist control ventilation

A
  • not always synchronised with the patient’s breathing
  • inappropriate triggering (e.g. hiccips) may lead to excessive minute ventilation
  • can’t control the tidal volume and a rise in resistance or fall in compliance could lead to inadequate ventilation
  • often requires sedation to achieve patient ventilatory synchrony
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what is pressure limited assist-control with volume guarantee

A
  • aka volume control with autoflow on drager
  • it’s like pressure pre-set assist control except that the tidal volume is set
  • the ventilator titrates the pressure to achieve the tidal volume
  • inspiratory pressure stays constant within the same breath
33
Q

what is pressure support mode

A
  • this is a spontaneous breathing mode
  • the operator sets the inspiratory pressure
  • the pt triggers a breath by passing either a flow or pressure threshold
  • the pre-set level of inspiratory pressure is then delivered
  • no breaths given if the pt does not initiate a breath
  • the ventilator goes from inspiration to expiration when the pt’s inspiratory flow falls below a pre-set proportion of the peak inspiratory flow
  • therefore the pt has some control over inspiratory time and tidal volume (through cycling) as well as resp rate and pattern (through triggering)
34
Q

advantages of pressure support mode

A
  • simple to set
  • avoids high inspiratory pressures
  • ## better patient-ventilator synchrony, less sedation required
35
Q

disadvantages of pressure support mode

A
  • no apnoea back-up in older ventilators
  • change in lung compliance or resistance results in change in tidal volume
36
Q

what is CPAP

A
  • constant positive airway pressure during inspiration and expiration
  • splints open alveoli
  • this reduces shunting
  • reduces recurrent opening and closing of alveoli with each breath which can lead to lung injury
  • inspiration starts from that set baseline pressure and airway pressure returns to this level at the end of expiration
37
Q

What is SIMV

A
  • synchronised intermittent mandatory ventilation
  • patient receies a set number of mandatory breaths that are synchronised with the patient’s efforts to breathe
  • the mandatory breaths can be volume control or pressure control
  • they can also take additional breaths between these mandatory breaths which are pressure supported
  • whether the pt triggers a synchronised mandatory breath or a pressure support breath depends whether they trigger during the SIMV period or during the spontaneous period
38
Q

what is the required minute ventilation for healthy adults

A

100-120ml/kg/min of minute ventilation

39
Q

what is the formula for tidal volume

A

4-8ml/kg predicted body weight

40
Q

what is the set inspiratory pressure

A

set inspiratory pressure is usually, but not always, set as pressure above PEEP

41
Q

the sum of PEEP and set inspiratory pressure should be:

A

<30cmH2O

42
Q

what is the respiratory cycle time and what is it composed of?

A

Respiratory cycle time = 60/respiratory rate

respiratory cycle time can be split into:
- inspiratory time
- expiratory time

43
Q

what is expiratory time

A

it is not set it’s just the time left between the end of one inspiration and the beginning of the next

44
Q

inspiratory time is composed of

A
  • inspiratory flow time
  • a period when lungs are held inflated but there is neither flow in, nor out (inspiratory pause time)
45
Q

if tidal volume is kept the same what will happen to time if you increase flow

A

time will go down because time = volume/flow

46
Q

airway pressure =

A

airway pressure = flow x resistance + (volume/compliance) + PEEP

47
Q

how is airway pressure related to flow and inspiratory flow time

A

airway pressure is directly relate to flow and inversely related to inspiratory flow time

48
Q

PEEP 0 is recommended for which patients

A

patients with asthma or COPD who are not taking spontaneous breaths

49
Q

adverse effects of increasing FiO2 and range of values that is associated with low risk of adverse events

A
  • oxygen toxicity
  • low risk of adverse events between 0.21 and 0.5
50
Q

possible adverse effects of increasing PEEP

A
  • CVS effects due to increased intrathoracic pressure
  • increase in alveolar and airway pressures with risk of barotrauma
51
Q

PEEP range that’s usually safe

A

0-10

52
Q

adverse effect of increasing insp. time

A
  • shorter expiratory time with risk of gas trapping
  • cvs effects due to increased mean intrathoracic pressure
53
Q

insp. times associated with low risk of adverse effects

A

<50% respiratory cycle

54
Q

adverse effects associated with increasing tidal volume or increasing insp. pressure

A

increase in insp pressure increase risks of barotrauma
also it only has a minor effect on oxygenation

55
Q

range of tidal volume that is associated with low risk of adverse effects

A

tidal volume <8ml/kg

56
Q

inspiratory pressure that is low risk

A

insp. pressure including PEEP of <30mmH2O

57
Q

adverse effect of increasing inspiratory pause

A

drop in inspiratory flow time

58
Q

inspiratory pause range that is low risk

A

5-10% of respiratory cycle time

59
Q

what should you titrate minute ventilation against? and why

A
  • in general should be titrated against pH rather than PaCO2
    • this is because the effects of PaCO2 are generally mediatef by pH
  • except in raised ICP when PaCO2 needs to be monitored closely
60
Q

three ways to increase alveolar ventilation

A

increase tidal volume
increase resp rate
eliminate excessive circuit dead space

61
Q

adverse effects of increasing resp rate

A

shorter expiratory time –> gas trapping –> barotrauma and haemodynamic compromise

62
Q

what is the relationship between airway pressure and alveolar presure

A
  • airway pressure = flow x resistance + alveolar pressure
  • at the end of inspiration there is no flow so airway pressure = (0xresistance) + alveolar pressure
  • therefore at the end of inspiration airway pressure = alveolar pressure
  • this is known as the inspiratory pause pressure
  • this can be measured by pressing the inspiratory pause hold control on ventilators (only in apnoeic patients) and measuring the pressure when it plateaus
  • this is aka the plateau pressure or inspiratory pause pressure
63
Q

elements that can lead to high airway pressure readings

A
  • circuit kinking
  • ett kinking
  • ett obstructed with sputum
  • endobronchial intubation
  • bronchospasm
  • reduced lung compliance
    • pulmonary oedema
    • consolidation
    • collapse
  • reduced pleural compliance
    • pneumothorax
  • reduced chest wall compliance
    • abdominal distention
  • patient ventilator dyssynchrony, coughing
64
Q

what is the first thing to do when the high pressure alarm sounds AND the patient in deteriorating

A

disconnect the pt from the ventilator and manually ventilate them

  • if the pt is easy to manually ventilate then the problem is in the vent or vent or circuit
  • if the pt is difficult to manually ventilate then the problem is in the ET tube or in the patient
65
Q

is it the alveolar pressure or the airway pressure that is important in terms of haemodynamic effects of ventilation and in terms of lung damage from ventilation

A

the alveolar pressure

66
Q

what should the plateau pressure be kept below in ventilated patients

A

kept <30 cmH2O

67
Q

equation for alveolar pressure

A

alveolar pressure = volume/compliance + PEEP

68
Q

what is the recommended tidal volume

A

4-8ml/kg ideal body weight

69
Q

how can you measure the total PEEP in ventilated apnoeic patients

A

expiratory pause hold button and looking at the plateau

70
Q

what are the components of total PEEP

A

set peep and intrinsic PEEP

71
Q

hypotension occuring immediately after the initiation of positive pressure ventilation is usually due to:

A
  • hypovolaemia –> exacerbated by reduced venous return due to positive intrathoracic pressure
  • induction drugs –> almost all anaesthetic agents cause vasodilation and myocardial depression
  • gas trapping due to over-enthusiastic ventilation
  • far less common but tension pneumothorax should always be considered
72
Q

what is the i:e ratio of a normal breathing pattern

A

1:2

73
Q

the problem in ventilating ARDS patients

A
  • in ARDS there is consolidation and collapse in dependent areas with relatively normal non-dependent areas
    • this would only be visible on CT not XR (think about it they’re lying down)
  • the compliance of dependent portions is therefore low while the compliance of non-dependent portions is relatively normal
  • most of the tidal volume will therefore go to the high compliance non-dependent regions so if a normal tidal volume is used then this can cause overdistention of the alveoli and volutrauma
  • because overall compliance is poor, the airway pressures required to meet a normal tidal volume will be high, putting the patient at risk of barotrauma
74
Q

basic strategy in ventilating during ARDS

A
  • to reopen alveoli and keep them open using high PEEP but with low tidal volumes
  • the effects of this are to:
    • reduce shunting –> improve oxygenation
    • improve overall compliance
    • reduce heterogeneity in complaince
    • reduce shear injury
  • overall result is more even ventilation and less over-distention
75
Q

pressure considerations for ventilating an asthmatic

A
  • primary problem is high airway resistance and therfore high airway pressures
    • airway pressure = flow x resistance + volume/compliance + PEEP
    • airway pressure = flow x resistance + alveolar pressure
  • since alveolar pressure rather than airway pressure is the important thing in terms of adverse effects then you can ignore high airway pressures needed to achieve adeqaute alveolar pressures
  • the plateau pressure (alveolar pressure) should be monitored instead of the airway pressure
  • in order to minimise gas trapping the expiratory time is lengthened (shortening the inspiratory time) this will also lead to greater flow and therefore higher pressures but again it doesn’t matter as it’s the alveolar pressures that need to be monitored
76
Q

touble shooting hypotension after initiation of ventilation

A
  • hypovolaemia (reduced venous return due to increased intrathoracic pressure) and anaesthetic drugs are by far the most common causes
  • the initial response should be small fluid boluses +/- short duration vasoconstrictor (norad or adrenaline)
  • if this fails to correct the hypotension then disconnect the patient from the ventilator - if it’s gas trapping then this will improve over the next 10-30 seconds
  • if none of the above works then consider tension pneumothorax and needle thoracostomy
77
Q

is pressure support mode an appropriate mode for patients that are making little or no effort to initiate breaths

A

no in pressure support mode they have to initiate all their breaths

78
Q

which ventilator modes for:
- largely apnoic patient
- pt taking intermittent spontaneous breaths
- an improving patient taking regular spontaneous breaths

A

Basic Course (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions