Post on 02-Apr-2018
7/27/2019 Modes of Ventilation - NRRCC 2007.pdf
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Mechanical VentilationMechanical VentilationUnderstanding ModesUnderstanding Modes
Rob Chatburn, RRTRob Chatburn, RRT--NPS, FAARCNPS, FAARC
Research ManagerResearch Manager Respiratory TherapyRespiratory Therapy
Cleveland ClinicCleveland Clinic
Associate ProfessorAssociate Professor
Case Western Reserve UniversityCase Western Reserve University
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OverviewOverview
Characteristics of modes Pressure control vs volume control
Graphical representations of modes Breath types
Mandatory vs spontanous
Assisted vs unassisted
Breathing patterns Definitions, indications, examples
Graphical representations
Computer control of mechanicalventilation
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Characteristics of a ModeCharacteristics of a Mode
1. Breathing Pattern Control variable
Breath sequence
2. Control Type Setpoint, auto-setpoint, servo, adaptive, optimal
3. Control Strategy
Phase variables
Operational logic
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Control VariablesControl Variables
Ventilator can control only one variable at a timeIndependent variable is control variable
Pvent = E x V + R x V
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Volume ControlVolume Control
Tidal volume and flow presetAirway pressure changes with lung
mechanics
Advantage:
Minute ventilation and gas exchange stable
Disadvantage:
Volume and flow may not be optimal
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Pressure ControlPressure ControlAirway pressure preset
Volume and flow change with lungmechanics
Advantage: Better patient flow synchrony
Possibly better oxygenation
Potentially reduced risk of volutrauma
Disadvantage:
Gas exchange may not be stable
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VolumeVolume
ControlControlInfluenceInfluence
DiagramDiagram
MinuteVolume
TidalVolume Rate
CycleTime
Inspiratory
Time
Expiratory
Time
I:E
Inspiratory
Flow
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PressurePressure
ControlControlInfluenceInfluence
DiagramDiagram
MinuteVentilation
VentilatoryFrequency
TidalVolume
InspiratoryTime
ExpiratoryTime
I:E Ratio
PressureGradient
PeakInspiratoryPressure
EndExpiratoryPressure
Resistance
TimeConstant
Compliance
Mean
AirwayPressure
ContinuousFlow Rate
(Affects shapeof pressurewaveform)
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0 Time (s)
Inspiration Expiration
Volume/Flow ControlVolume/Flow Control
0 Time (s)Flow
Pressure Paw
Volume Plung
Paw
Inspiration Expiration
Pressure ControlPressure Control
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Dual ControlDual Control Volume control to Pressure Control:
Attempts to deliver a constant tidal volume whilelimiting peak pressure
Pressure control to Volume Control:
Attempts to limit peak pressure but assures tidalvolume delivery
Disadvantage:
Requires high degree of understanding
Difficult to adjust and maintain
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Characteristics of a ModeCharacteristics of a Mode
1. Breathing Pattern Control variable
Breath sequence
2. Control Type Setpoint, auto-setpoint, servo, adaptive, optimal
3. Control Strategy
Phase variables
Operational logic
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Breath TypesBreath Types
What is the difference between
mandatory and spontaneous breaths?
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Spontaneous
yes
no
Breath TypesBreath Types
Patient
controlssize
yes
Mandatory
no
Think
Patient
controlsstart
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Definition of Assisted BreathDefinition of Assisted Breath
Assisted Ventilator does work on patient.
Un-Assisted
Ventilator does no work on patient. Loaded (work imposed on patient)
Patient does work on ventilator.
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Identification of Assisted BreathsIdentification of Assisted Breaths
Assisted
Airway pressure rises above baseline duringinspiration (or falls below baseline duringexpiration).
Un-Assisted Airway pressure stays constant during inspiration
or expiration.
Loaded (work imposed on patient) Airway pressure falls below baseline during
inspiration and rises above baseline duringexpiration.
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Assisted Spontaneous BreathsAssisted Spontaneous Breaths
Pressure Support Volume Support
Automatic Tube Compensation Proportional Assist Ventilation
SmartCare
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Potential ConfusionPotential Confusion
An assisted breath may bespontaneous or mandatory
A spontaneous breath may beassisted or unassisted
A mandatory breath is assisted by
definition
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Characteristics of a ModeCharacteristics of a Mode
1. Breathing Pattern
Control variable
Breath sequence
2. Control Type Setpoint, auto-setpoint, servo, adaptive, optimal
3. Control Strategy
Phase variables
Operational logic
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Continuous MandatoryContinuous Mandatory
Ventilation (CMV)Ventilation (CMV)
Mandatory breaths Machine triggered and/or machine cycled
Spontaneous breaths
During mandatory breaths only, not between
Key clinical concept
Level of support independent of frequency (ifpatient is breathing)
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Intermittent MandatoryIntermittent Mandatory
Ventilation (IMV)Ventilation (IMV)
Mandatory breaths Machine triggered and/or machine cycled
Spontaneous breaths
Between and during mandatory breaths
Key clinical concept
Level of support is proportional to set frequency(if spontaneous breaths unassisted)
Historically used as a mode of weaning
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Continuous SpontaneousContinuous Spontaneous
Ventilation (CSV)Ventilation (CSV)
All breaths spontaneous Patient triggered and cycled
No backup rate in case of apnea
Breaths may or may not be assisted
Full support may be achieved (if no apnea)
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Characteristics of a ModeCharacteristics of a Mode
1. Breathing Pattern
Control variable
Breath sequence
2. Control Type Setpoint, auto-setpoint, servo, adaptive, optimal
3. Control Strategy
Phase variables
Operational logic
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8 Basic Breathing Patterns8 Basic Breathing PatternsControl
Variable
Breath
Sequence Symbol
Continuous Mandatory Ventilation VC-CMV
Intermittent Mandatory Ventilation VC-IMV
Continuous Mandatory Ventilation PC-CMV
Intermittent Mandatory Ventilation PC-IMV
Continuous Spontaneous Ventilation PC-CSV
Continuous Mandatory Ventilation DC-CMV
Intermittent Mandatory Ventilation DC-IMV
Continuous Spontaneous Ventilation DC-CSV
Dual
Pressure
Volume
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VCVC--CMVCMV
Often referred to as Assist/Control
Characteristics
VC results in more even distribution of ventilationamong lung units with equal resistance and unequalcompliance than PC
Selection of flow and sensitivity is critical
Indications Need for total ventilatory support
Need for precise regulation of blood gases
Example Precise regulation of PaCO2 in patients with traumatic
brain injury
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VCVC--CMVCMV
waveformswaveforms
Ven
tilato
r
Pressu
re
Vo
lume
Flo
w
Mu
sc
le
Pressure small
inspiratory
effort
large
inspiratory
effort
no
inspiratory
effort
A B C
patient
triggered
machine
triggered
reducedpressure
indicates patient
effort throughoutinspiration
set tidal volume
setflow
VC IMV
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VCVC--IMVIMV
Characteristics Spontaneous breaths may be assisted
Selection of mandatory flow and spontaneouspressure support critical
Indications Relatively normal lung function
Rapid recovery from sedation or respiratory failure
Recent data suggest it is worst choice for weaning
ExampleTreatment of neuromuscular disease like Gullian-Barre syndrome
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VCVC--IMVIMV
waveformswaveforms
Ven
tilato
r
Pressur
e
Vo
lume
Flo
w
Mus
cle
Pres
sure small
inspiratory
effort
no
inspiratory
effort
A B C
patient
triggered
machine
triggered
medium
inspiratory
effort
setpressure support
settidal volume
setflow
Are spontaneous
breaths assisted?
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PCPC--CMVCMV Characteristics
PC results in more even distribution of ventilationamong lung units with equal compliance and unequalresistance than VC
Pressure control results in higher mean airway
pressure and earlier lung opening than VC
Indications Problems with oxygenation or synchrony
Example Treatment of ARDS patients with oxygenation
problems
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PCPC--CMVCMV
waveformswaveforms
Ven
tilat
or
Pressure
Vo
lume
Flo
w
Musc
le
Pres
sure small
inspiratory
effort
large
inspiratory
effort
no
inspiratory
effort
A B C
patient
triggered
machinetriggered
time cycled
setpressure limit
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PCPC--IMVIMV Characteristics
Relatively simple mode Used historically for infants
Spontaneous breaths may be assisted
Indications Problems with oxygenation or synchrony
Adequate ventilatory drive
Example Treatment of premature infants with RDS
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PCPC--IMVIMV
waveformswaveforms
Ven
tilato
r
Pressure
Vo
lume
Flo
w
Mus
cle
Pressure large
inspiratory
effort
no
inspiratory
effort
A CBmedium
inspiratory
effort
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PCPC--CSVCSV
Characteristics No assist = CPAP
Assist Pressure Support
Proportional Assist
Automatic Tube Compensation
Indications Weaning
Reduce work of breathing or stabilize oxygenation Examples
Nasal CPAP for neonates recovering from RDS
Noninvasive ventilation of adults
A B C
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PCPC--CSVCSV
waveformswaveforms
Spontaneous
breaths are not
assisted
(CPAP)
Ven
tila
tor
Pressu
re
Vo
lume
Flo
w
Mu
sc
le
Pre
ssure small
inspiratory
effort
large
inspiratory
effort
no
inspiratory
effort
A B C
DCDC CMVCMV
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DCDC--CMVCMV
Characteristics
Mandatory breaths adapt to changing lungmechanics
Indications
Unstable lung mechanics or ventilatory drive
Example
Treatment of patient with pneumonia andintermittent secretion problems
A B
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DCDC--CMVCMV
waveformswaveforms
Ven
tilato
r
Pressu
re
Vo
lume
Flo
w
Mu
sc
le
Pres
sure
large
inspiratory
effort
no
inspiratory
effort
A B
patient
triggered
pressure limit
over-ridden
set volume target volume cycled
flow cycledsetflow limit
setpressure limit
switch frompressure control
to volume control
volume target
not met
inspiratory flowequals flow limit
volume metbefore
flow decays to set limit
pressure-to-volume
Bird VAPS
A B
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DCDC--CMVCMV
waveformswaveforms
volume-to-pressure
DrgerPressure Limited
VentilationV
en
tilato
r
Pressu
re
Vo
lume
Flo
w
Mu
sc
le
Pre
ssure small
inspiratory
effort
A B
set tidal volume
volume
limited
plateau
pressure
plateau
pressure
set Pmax
switch fromvolume control
to pressure control
volume limited
time cycledtime cycled
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DCDC--IMVIMV
waveformswaveforms
Ven
tilato
r
Pressure
Vo
lume
Flo
w
Mus
cle
Pressure
A C
plateau
pressure
set Pmax
time cycled
set Pmax
time cycled
set tidal volume
setflow
B
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Pressure SupportPressure Support
Pressure or flow triggered, pressurelimited, inspiratory flow cycled
Level of ventilatory support
determined by pressure limit
Sometimes set to approximately
support resistive work of breathing(through endotracheal tube)
A B C
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PCPC--CSVCSV
waveformswaveforms
Spontaneous
breaths are
assistedV
en
tilat
or
Pressur
e
Vo
lume
Flo
w
Mus
cle
Pressure small
inspiratory
effort
large
inspiratory
effort
no
inspiratory
effort
A B C
patient
triggered
flow cycled
setpressure limit
flow cycle threshold
pressure rise
time
increased
P i l A iP ti l A i t
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Proportional AssistProportional Assist
flowRvolumeEP normalnormalmus +=
( ) ( ) flowRRvolumeEEP abnormalnormalabnormalnormalmus +++=
( ) ( )loadabnormalloadnormalPmus +=
( ) ( )loadabnormalloadnormalPP ventmus +=+
flowRvolumeEloadabnormalP abnormalabnormalvent +==
operator settings (volume and flow amplification factors)
A B C
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PCPC--CSVCSV
waveformswaveforms
Spontaneous breaths
are assisted
(Proportional Assist)V
en
tilat
or
Pressure
Vo
lume
Flo
w
Mus
cle
Pres
sure small
inspiratory
effort
large
inspiratory
effort
no
inspiratory
effort
A B C
A t ti T bA t ti T b
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Automatic TubeAutomatic Tube
CompensationCompensation
2flowRloadresistiveabnormalP
tubevent
==
operator sets tube diameter
ventilator calculates resistance factor
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Characteristics of a ModeCharacteristics of a Mode1. Breathing Pattern
Control variable
Breath sequence
2. Control Type Within breaths Between breaths
3. Specific Control Strategy Phase variables
Operational logic
Evolution of Ventilator Control TypesEvolution of Ventilator Control Types
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ypyp
PatientVentilatorOperator
PatientVentilator
ModelOperator
PatientVentilator
Model
Strategic Control (between breaths)
adaptive (CMV+AutoFlow)
optimal (ASV)
ventilator-selected, dynamic setpoints
static model
Intelligent Control (between patients)
knowledge based
arti ficial neural network
ventilator-selected, dynamic setpoints
dynamic modelability to learn from experience
operator-selected, static setpoints
Tactical Control (within-breaths)
setpoint (PC-IMV)
auto-setpoint (Pmax)
servo (Automatic Tube Compensation)
T ti l C t lTactical Control
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Tactical ControlTactical Control
All the modes discussed so far All require the operator to set
Pressure (PIP, PEEP) Volume (tidal volume, minute ventilation) Flow (peak inspiratory flow)Time (inspiratory time, frequency, I:E)
Strategic ControlStrategic Control
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Strategic ControlStrategic Control
Characteristics Breathing pattern may be PC-CMV, PC-IMV, PC-CSV
Pressure limit automatically adjusted to compensate forchanges in compliance to meet target tidal volume
Indications (Self) Weaning
Reduce work of breathing or stabilize oxygenation Reduce clinician workload
Examples
Post-operative patients with normal lungs Mixed ICU patients COPD exacerbation
A B C
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AdaptiveAdaptive
ControlControl
Ven
tilat
or
Pressure
Vo
lume
Flo
w
Musc
le
Pres
sure
large
inspiratory
effort
no
inspiratory
effort
patienttriggeredmachinetriggered
pressure limit
automatically reduced
volume targetvolume overshoot
time cycled
Hamilton Galileo Adaptive Support ModeHamilton Galileo Adaptive Support Mode
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Hamilton Galileo Adaptive Support ModeHamilton Galileo Adaptive Support Mode
Optimum control Clinician enters
Patient ideal body weight Percent of predicted minute ventilation to support
Ventilator monitors
minute ventilation lung mechanics (expiratory time constant)
Automatically adjusts minute ventilation mandatory breath frequency
pressure limit inspiratory time
Sets frequency to minimize WOB as if
patient was breathing spontaneously
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Any medicalinstrumentation that
requires constant
input from a human
operator is obsoleteHamilton Medical
Intelligent ControlIntelligent Control
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Intelligent ControlIntelligent Control Characteristics
Classification of patient condition Manual (eg, by diagnosis)
Fuzzy logic Rule based expert system or artificial neural network
Indications
Weaning Respiratory failure of various typesTrauma
Examples Post-operative patients with normal lungs Mixed ICU patients Emergency department
C i l E lC i l E l
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Commercial ExampleCommercial Example
SmartCare (Drger Evita XL) Knowledge Based Control
1. Automatically adjust pressure support: breathing rate, tidalvolume and end tidal CO2.2. Automatically test patient tolerance of a lower pressure
support level without leaving the comfort zone.3. Attempts extubation with PS at resistive WOB.
Artificial intelligence Fuzzy logic interprets patient condition Rule based expert system treats condition
Operator sets patient weight history (neuro or COPD) type of airway
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Characteristics of a ModeCharacteristics of a Mode1. Breathing Pattern
Control variable
Breath sequence
2. Control Type Setpoint, auto-setpoint, servo, adaptive, optimalknowledge based
3. Specific Control Strategy Phase variables
Operational logic
Mode Description UtilityMode Description Utility
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Mode Description UtilityMode Description Utility
Describe the difference in modes
Pressure Support
Volume Support
Describe the difference in ventilators
Pressure support (PB7200)
Pressure support (Servo-i)
Mode Description SummaryMode Description Summary
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p yp y
(without the brand jargon)(without the brand jargon)
Pressure Support
Only Level 1 needed
PC-CSV
Volume Support Requires Level 2
PC-CSV with adaptive control
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Adaptive Pressure ControlAdaptive Pressure Control Pressure Regulated Volume Control
AutoFlow
VC+
PC-SIMV + Volume Guarantee
Mode Description SummaryMode Description Summary
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p y
(without the brand jargon)(without the brand jargon)
Level 3 Pressure Support
PB 7200 Cannot adjust rise time (limit variable)
Cannot adjust cycle threshold (cyclevariable)
Servo-i Adjustable rise time (limit variable)
Adjustable cycle threshold (cycle variable)
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ResourcesResources Get the book
college level textbook
300 pages
www.aarc.org/store Training Software
www.VentWorld.com
www.Amazon.com
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Too Complicated?Too Complicated?
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Final ThoughtFinal Thought If you explain something so
simply that even a fool can
understand it, then only a
fool will understand it."
FP Primiano Jr