Modes of Ventilation

Question 1

Goals of Mechanical Ventilation

Answer 1

Maintain homeostasis

Question 2

OR Goal of MV

Answer 2

ensure adequate oxygenation and CO2 removal for safe and effective surgery

Question 3

ICU goal of MV

Answer 3

treatment for severe respiratory distress
provide lungs with a “break” to rest and heal
decrease O2 consumption by providing rest for respiratory muscles

Question 4

Flow

Answer 4

the amount of air moving through a system

Question 5

Pressure

Answer 5

amount of force you build to distend lung

Question 6

Driving Pressure:

Answer 6

peak plateau pressure- PEEP

Question 7

restrictive pressure

Answer 7

overall pressure required to overcome pressure in airways

Question 8

distending pressure

Answer 8

required to open up lungs to open up lunges to provide gas exchange

Question 9

Peak Inspiratory Pressure

Answer 9

PiP
total pressure required to distend lungs and airways
pressure used to calculate dynamic compliance
signals pressure required to overcome both intrinsic factors and chest wall (extrinsic factors) to distend both pressure

Question 10

Plateau Pressure

Answer 10

distending pressure to extend only the lungs
measure redistribution of air flow through the lungs
used to calculate static compliance
Measures intrinsic factors of lung compliance

Question 11

How do you measure plateau pressure?

Answer 11

during an inspiratory hold

Question 12

Control Variables

Answer 12

respiratory Rate
tidal volume
pressure (Pip/PAW/Pplateau)
I:E ratio

Question 13

4 Parts of Respiratory Cycle

Answer 13

start of inspiration
inspiration itself
end of inspiration
expiration

Question 14

Components of a breath

Answer 14

Ti
Te
TCT (total cycle time)

Question 15

Total respiratory Cycle variables

Answer 15

impact how each mechanical breath is initiated sustain and terminated
trigger variable (start of inspiration)
limit variable (maintenance of inspiration)
cycling variable (transition to expiration)
Baseline variable (end expiration)

Question 16

Trigger Variable

Answer 16

represents the start of inspiration

can be affected with or w/o pt inspiratory effort by either Pressure, Volume, flow or time

Question 17

trigger variable (pressure)

Answer 17

pressure decrease in circuit stimulates ventilator to deliver breath

Question 18

Trigger Variable as Volume

Answer 18

volume change in circuit can stimulate ventilator to deliver breath

Question 19

Trigger Variable as flow

Answer 19

change in flow in circuit stimulates ventilator to deliver breath

Question 20

Trigger Variable as time

Answer 20

set time interval triggers ventilator to deliver breath (occurs independent of pt effort)

Question 21

Limit Variable

Answer 21

controls how an inspiratory breath is maintained once threshold is reached variable will not exceed set limit

Question 22

Limit variable does not

Answer 22

cause termination of inspiration

Question 23

Pressure as the limit variable

Answer 23

sets upper pressure limit that cannot be exceeded

stops airway pressure, but maintains breath

Question 24

Volume as the limit variable

Answer 24

set upper volume limit that cannot be exceeded

decrease flow in gas, but Vt maintained

Question 25

Flow as the limit variable

Answer 25

sets maximum airflow that cannot be exceeded | used in ICU

Question 26

Cycling Variable

Answer 26

transition from inspiration to expiration

Question 27

Volume as Cycling variable

Answer 27

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

Question 28

Pressure as cycling variable

Answer 28

once pressure achieved flow will transition to expiration

Question 29

Flow as cycling variable

Answer 29

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

Question 30

Time as cycling variable

Answer 30

ventilator terminated inspiratory breath after pre-determined inspiratory time has been delivered

Question 31

What is the most common cycling variable

Answer 31

time (d/t NMB)

Question 32

Baseline variable

Answer 32

pressure maintained in the circuit at end expiration (PEEP) must be individualized to patient used to prevent atelectasis

Question 33

PEEP

Answer 33

alveolar pressure above atmospheric

Question 34

Goal of PEEP

Answer 34

to improve oxygenation

Question 35

Intrinsic PEEP

Answer 35

secondary to incomplete expiration auto peep incomplete breath prior to initiation of next breath causes progressive air trapping

Question 36

extrinisc PEEP

Answer 36

provided by mechanical ventilator | applied PEEP

Question 37

Causes of AUTO PEEP

Answer 37

high Minute ventilation expiratory flow limitation expiratory resistance

Question 38

Volume Control Ventilation (VCV)

Answer 38

``` delivers set tidal volume as set respiratory rate time is trigger variable volume is limit variable time is cycling variable airflow will remain constant ```

Question 39

What changes in VCV?

Answer 39

airway pressure (PIP/Pplateau) will change on a breath. by breath basis during this mode of ventilation based on changing respiratory compliance

Question 40

Why choose VCV?

Answer 40

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

Question 41

Pressure Control Ventilation

Answer 41

Delivers set inspiratory pressure as set RR time is trigger variable pressure is limit variable time is cycle variable

Question 42

in PCV, what is controlled by user?

Answer 42

airway pressures volumes change breath by breath basis depending on total respiratory system compliance

Question 43

Why choose PCV?

Answer 43

set pressure limit to avoid barotrauma from delivery of excessive pressure decelerating flow pattern allows for homogenous distribution of inspired gas throughout lung must set patient appropriate high and low VT alarms as change in respiratory compliance can affect Vt delivery

Question 44

Pressure control-volume guarantee (PCV-VG)

Answer 44

respiratory cycle variables are same as PCV, but ventilator adjust pressure delivered if current volume is not set volume adjustments take 3-5 breaths to complete can allow for atelectasis development if compliance decreases and ventilator is delayed in providing adequate pressure to distend lungs

Question 45

Most common mode of ventilation

Answer 45

PCVVG

Question 46

Variables for PCV-VG

Answer 46

trigger: time limit: pressure cycling: time

Question 47

SIMV

Answer 47

synchronized intermittent mandatory ventilation delivers a set Vt at a set RR in conjunction with patients initiated breathes time/patient : trigger variable flow or volume (if in VCV) are limit variables volume is cycle variable patient initiated breaths are not supported (unless in SIMV-PSV)

Question 48

Why chose SIMV

Answer 48

useful when weaning from controlled mechanical ventilation to spontaneous respiration (less desynchrony) with pt initiated breaths

Question 49

When does Hypoventilation occur in SIMV

Answer 49

if set Vt and RR are too low adn patient's spontaneous respiration effort adequate

Question 50

When does hyperventilation occur in SIMV

Answer 50

if using SIMV- PSV and pressure support level too high

Question 51

Pressure support ventilation

Answer 51

supported mode of ventilation for spontaneously breathing patient pressure support level set by user patient is trigger varaible 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

Question 52

Why choose PSV?

Answer 52

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 controlled, changes in respiratory system compliance will alter Vt delivered

Question 53

High PIP pressures with normal peak plateau pressures indicate

Answer 53

resistance problem

Question 54

What are resistance problems

Answer 54

``` small ET tube kinking bitiing obstructed ET tube high flow rate or Vt ventilator asynchrony mucous plug, blood clot bronchospasm ```

Question 55

High PIP and HIgh peak plateau pressures indicate

Answer 55

compliance problem

Question 56

What are compliance problems

Answer 56

``` ARDS, edema, ateletasis pneumothorax, effusion air trapping (auto peep) R mainstem intubation fibrosis, ILDs obesity abd compartment syndrome ```