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N942/N928 Basics of Anesthesia > Modes of Mechanical Ventilation > Flashcards

Modes of Mechanical Ventilation Flashcards

1
Q

2 types of pressure measurements

A

peak inspiratory pressure

plateau pressure

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2
Q

Peak inspiratory pressure

A

total pressure required to distend lungs and airways

pressure used to calculate dynamic compliance (intrinsic and extrinsic factors)

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3
Q

plateau pressure

A

distending pressure to expand only lungs (intrinsic)
measures redistribution of air flow through lungs
Pplat is used to calculate static compliance

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4
Q

when can you measure Pplat

A

only in volume control during inspiratory hold

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5
Q

4 parts of each breath

A 
start of inspiration (trigger variable)
inspiration itself (limit or target variable)
end of inspiration (cycling variable, transition to expiration)
expiration (baseline variable, end expiration, PEEP)
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6
Q

3 components of a breath

A

ti=inspiratory time
te=expiratory time
TCT=total cycle time

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7
Q

4 types of trigger variables

A

pressure
volume
flow
time

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8
Q

pressure trigger variable

A

decrease in circuit stimulates ventilator to deliver breath

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9
Q

volume

A

volume change in circuit can stimulate ventilator to deliver breath

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10
Q

flow

A

change of flow in circuit stimulates ventilator to deliver

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11
Q

time

A

set time interval triggers ventilator to deliver breath (set by RR). this occurs independent of patient effort

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12
Q

limit variable

A

controls how an inspiratory breath is maintained once threshold is reached variable will not exceed set limit. this does NOT cause termination of inspiration

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13
Q

pressure as limit variable

A

sets upper pressure limit that cannot be exceeded

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14
Q

volume as limit variable

A

set upper volume limit that cannot be exceeded

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15
Q

flow as limit variable

A

sets maximum airflow that cannot be exceeded

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16
Q

cycling variable

A

transition from inspiration to expiration. based on either volume, pressure, flow, or time

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17
Q

volume cycling variable

A

ventilator delivers flow until set volume achieved. if inspiratory pause set (typically 10-20%) this variable changes to a time based cycling variable

18
Q

pressure cycling variable

A

once pressure is achieved, flow will transition to expiration

19
Q

flow cycling variable

A

once inspiratory flow drops below set threshold (default at 25%), ventilator will transition to expiration. noted in pressure support ventilation mode

20
Q

time cycling variable

A

ventilator terminated inspiratory breath after predetermined inspiratory time has been delivered

21
Q

intrinsic peep

A

secondary to incomplete expiration, referred to as auto peep (related to air trapping, MV or RR maybe too high)

22
Q

extrinsic peep

A

provided by a mechanical ventilator, referred to as applied peep

23
Q

auto peep causes

A

high MV, expiratory flow limitation, expiratory resistance

24
Q

volume control ventilation
trigger variable
limit variable
cycling variable

A

delivers set TV at set RR
time
volume
flow

25
Q

VCV PIP/Plat and airflow

A 
airway pessure (PIP/plat) will change on a breath by breath basis during this mode of ventilation based on changing respiratory compliance. airflow will remain constant. 
(looks like sharks tooth on vent)
26
Q

why choose VCV

A

maintenance of set minute ventilation through direct manipulation of TV and RR
remember to set individualized alarms to protect patient
increasing airway or lung resistance will stimulate generation of higher pressure to deliver set TV

27
Q

PCV
trigger variable
limit cariable
cycle variable

A

delivers set inspiratory pressure at set respiratory rate
time
pressure
time
TV changes on breath by breath basis based on compliance
good to control barotrauma

28
Q

PCV on ventilator

A 
decelerating wave flow (allows for homogenous distribution)
pPeak plateaus (not sharks tooth like VCV)
29
Q

why choose PCV

A

set pressure limit to avoid barotrauma from delivery of excessive pressure
decelerating flow pattern allows for homogenous distribution of inspired gas throughout lungs
theoretically improves ventilation pattern and decreases WOB
compliance change means volume delivery change

30
Q

Pressure Control-Volume Guarantee (PCV-VG)
trigger variable
cycling variable
delivery variable

A

respiratory cycle variables mirror PCV, however ventilator adjust pressure delivered if current volume is not set volume
adjustments take 3-5 breaths to complete (can be de recruitment)
can allow for atelectasis development if compliance decreases and ventilator is delayed in providing adequate pressure to distant lungs
time is trigger variable and cycling variable
pressure is delivery variable

31
Q

SIMV
trigger variable
limit variable
cycle variable

A

delivers set TV at a set RR in conjunction with patient initiated breaths
time or patient is trigger variable (if pt takes breath its them)
flow is limit variable
volume is cycle variable
helps demote dsynchrony
can apply this mode in many ways
patient initiated breaths are not supported unless in SIMV-PSV

32
Q

SIMV modes

A

SIMV-VC
SIMV-PC
SIMV-PCG
SIMV-PSV

33
Q

why choose SIMV

A

useful when weaning from controlled mechanical ventilation
less dysyncrhony with patient initiated breaths
hypoventilation can occur if set TV and RR are too low and the patients spontaneous respiration effort is inadequate
hyperventilation can also occur if using SIMV-PSV and pressured support level too high
not retimed based on pt breath

34
Q

PSV
trigger variable
limit variable
cycle variable

A

supported mode of ventilation for spontaneously breathing patient
patient is trigger variable
pressure is limit variable
flow is cycle variable
patient controls most aspects of ventilation but the anesthetist can adjust certain variables to augment or limit support given to prepare patient for extubation
defaults to SIMV PSV if they dont breathe

35
Q

why choose PSV

A

great for end of case in preparation for extubation
patient must be breathing spontaneously or ventilator will switch to backup mode
just like PCV, pressure is controlled, changes in respiratory system compliance will alter TV delivered

36
Q

how to wean in PSV

flow trigger

A

slowly increase this as minute ventilation increases so once they hit the flow (.2 and up), then you know they can take an adequate breath (at least 2l/min)

37
Q

how to wean in PSV

trigger window

A

% of time patient breath will be supported by ventilator

38
Q

end of breath % peak flow

A

transition from inspiratory to expiratory breath

39
Q

backup time

A

how long people can be apneic before backup mode (10-30seconds)

40
Q

Tinsp

A

inspiratory time in seconds

N942/N928 Basics of Anesthesia (5 decks)

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