Modes of Mechanical Ventilation

Question 1

2 types of pressure measurements

Answer 1

peak inspiratory pressure

plateau pressure

Question 2

Peak inspiratory pressure

Answer 2

total pressure required to distend lungs and airways

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

Question 3

plateau pressure

Answer 3

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

Question 4

when can you measure Pplat

Answer 4

only in volume control during inspiratory hold

Question 5

4 parts of each breath

Answer 5

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)

Question 6

3 components of a breath

Answer 6

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

Question 7

4 types of trigger variables

Answer 7

pressure
volume
flow
time

Question 8

pressure trigger variable

Answer 8

decrease in circuit stimulates ventilator to deliver breath

Question 9

volume

Answer 9

volume change in circuit can stimulate ventilator to deliver breath

Question 10

flow

Answer 10

change of flow in circuit stimulates ventilator to deliver

Question 11

time

Answer 11

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

Question 12

limit variable

Answer 12

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

Question 13

pressure as limit variable

Answer 13

sets upper pressure limit that cannot be exceeded

Question 14

volume as limit variable

Answer 14

set upper volume limit that cannot be exceeded

Question 15

flow as limit variable

Answer 15

sets maximum airflow that cannot be exceeded

Question 16

cycling variable

Answer 16

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

Question 17

volume cycling variable

Answer 17

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

Question 18

pressure cycling variable

Answer 18

once pressure is achieved, flow will transition to expiration

Question 19

flow cycling variable

Answer 19

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

Question 20

time cycling variable

Answer 20

ventilator terminated inspiratory breath after predetermined inspiratory time has been delivered

Question 21

intrinsic peep

Answer 21

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

Question 22

extrinsic peep

Answer 22

provided by a mechanical ventilator, referred to as applied peep

Question 23

auto peep causes

Answer 23

high MV, expiratory flow limitation, expiratory resistance

Question 24

volume control ventilation
trigger variable
limit variable
cycling variable

Answer 24

delivers set TV at set RR
time
volume
flow

Question 25

VCV PIP/Plat and airflow

Answer 25

``` 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) ```

Question 26

why choose VCV

Answer 26

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

Question 27

PCV trigger variable limit cariable cycle variable

Answer 27

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

Question 28

PCV on ventilator

Answer 28

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

Question 29

why choose PCV

Answer 29

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

Question 30

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

Answer 30

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

Question 31

SIMV trigger variable limit variable cycle variable

Answer 31

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

Question 32

SIMV modes

Answer 32

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

Question 33

why choose SIMV

Answer 33

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

Question 34

PSV trigger variable limit variable cycle variable

Answer 34

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

Question 35

why choose PSV

Answer 35

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

Question 36

how to wean in PSV | flow trigger

Answer 36

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)

Question 37

how to wean in PSV | trigger window

Answer 37

% of time patient breath will be supported by ventilator

Question 38

end of breath % peak flow

Answer 38

transition from inspiratory to expiratory breath

Question 39

backup time

Answer 39

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

Question 40

Tinsp

Answer 40

inspiratory time in seconds