New Modes of Mechanical New Modes of Mechanical Ventilation Ventilation Mazen Kherallah, MD, Mazen Kherallah, MD, FCCP FCCP Consultant Consultant Intensivist Intensivist
Dec 22, 2015
New Modes of Mechanical New Modes of Mechanical VentilationVentilation
Mazen Kherallah, MD, Mazen Kherallah, MD, FCCPFCCP
Consultant IntensivistConsultant Intensivist
King Faisal Specialist King Faisal Specialist HospitalHospital
Key Ideas for Key Ideas for Understanding Understanding
Mechanical VentilationMechanical Ventilation1.1. Mathematical ModelsMathematical Models
– Equation of motionEquation of motion– Time constantTime constant– Mean airway pressureMean airway pressure
2.2. Control VariablesControl Variables– Pressure, volume, dualPressure, volume, dual
3.3. Phase VariablesPhase Variables– Trigger, Limit and CycleTrigger, Limit and Cycle
4.4. Breath Types/PatternsBreath Types/Patterns5.5. Optimum Mode SelectionOptimum Mode Selection
elastance = pressure / volume
volume
transairwaypressure
transthoracicpressure
transrespiratorypressure
Lung Lung MechanicMechanic
ssresistance = pressure / flow
flow
Equation of MotionEquation of Motion
ventilationpressure(to deliver
tidal volume)
=elastic
pressure(to inflate lungs and chest wall)
+resistivepressure
(to make air flow through the
airways)
P = R x V + E x V
P = Presistive + Pelastance
Phase VariablesPhase Variables
• Trigger (start)- begins inspiratory flowTrigger (start)- begins inspiratory flow• Cycling (end)- ends inspiratory flowCycling (end)- ends inspiratory flow• Limiting (continue)- places a maximum value Limiting (continue)- places a maximum value
on a “control variable”on a “control variable”– pressurepressure– volumevolume– flowflow
– timetime
Trigger Variable- Trigger Variable- Start of a BreathStart of a Breath
• Time - Time - control ventilationcontrol ventilation• Pressure - Pressure - patient assistedpatient assisted• Flow - Flow - patient assistedpatient assisted• Volume - Volume - patient assistedpatient assisted• Manual - Manual - operator controloperator control
Inspiratory - delivery Inspiratory - delivery limitslimits
• Maximum value that can be Maximum value that can be reached but will not end the reached but will not end the breath-breath-– VolumeVolume– FlowFlow– PressurePressure
End of Insp…cycle End of Insp…cycle mechanismsmechanisms
• The phase variable used to The phase variable used to terminate inspiration-terminate inspiration-– VolumeVolume– PressurePressure– FlowFlow– TimeTime
Breath Type… Only Two Breath Type… Only Two (for now)!(for now)!
• MandatoryMandatory– Ventilator does the workVentilator does the work– Ventilator controls start and stopVentilator controls start and stop
• SpontaneousSpontaneous– Patient takes on workPatient takes on work– Patient controls start and stopPatient controls start and stop
The Control Variable-The Control Variable-Inspiratory Breath Inspiratory Breath
DeliveryDelivery• Flow (volume) controlledFlow (volume) controlled
– pressure may varypressure may vary
• Pressure controlledPressure controlled– flow and volume may varyflow and volume may vary
• Time controlled (HFOV)Time controlled (HFOV)– pressure, flow, volume may varypressure, flow, volume may vary
Inspiration Expiration
0 1
20
00 1 2
3
-3
0
20
021
20
00 1 2
3
-3
0
20
02
Inspiration Expiration
Volume/Flow Control Pressure Volume/Flow Control Pressure ControlControl
Time (s) Time (s)
PawPaw
Pressure
Volume
Flow
If compliance decreases the pressure increases to maintain the same Vt
Volume Control Breath TypesVolume Control Breath Types
11 22 33 44 55 66
SECSEC
11 22 33 44 55 66
PPawaw
cmHcmH2200
6060
-20-20
120120
120120
SECSEC
INSPINSP
EXHEXH
FlowFlowL/minL/min
New Modes of VentilationNew Modes of VentilationDual-Controlled ModesDual-Controlled Modes
TypeType Manufacturer; Manufacturer; ventilatorventilator
NameName
Dual control within a Dual control within a breathbreath
VIASYS Healthcare; Bird VIASYS Healthcare; Bird 8400Sti and Tbird8400Sti and Tbird
VIASYS Healthcare; Bear VIASYS Healthcare; Bear 10001000
Volume-assured pressure Volume-assured pressure supportsupport
Pressure augmentationPressure augmentation
Dual control breath to Dual control breath to breath:breath:
Pressure-limited flow-Pressure-limited flow-cycled ventilation cycled ventilation
Siemens; servo 300Siemens; servo 300
Cardiopulmonary Cardiopulmonary corporation; Venturicorporation; Venturi
Volume supportVolume support
Variable pressure Variable pressure supportsupport
Dual control breath to Dual control breath to breath:breath:
Pressure-limited time-Pressure-limited time-cycled ventilationcycled ventilation
Siemens; servo 300Siemens; servo 300
Hamilton; GalileoHamilton; Galileo
Drager; Evita 4Drager; Evita 4
Cardiopulmonary Cardiopulmonary corporation; Venturicorporation; Venturi
Pressure-regulated Pressure-regulated volume controlvolume control
Adaptive pressure Adaptive pressure ventilationventilation
AutoflowAutoflow
Variable pressure controlVariable pressure control
Dual control breath to Dual control breath to breath:breath:
SIMVSIMV
Hamilton; GalileoHamilton; Galileo Adaptive support Adaptive support ventilationventilation
Dual Control within a Dual Control within a BreathBreath
volume-assured pressure supportvolume-assured pressure support• This mode allows a feedback loop based on This mode allows a feedback loop based on
the volumethe volume• Switches even within a single breath from
pressure control to volume control if minimum tidal volume has not been achieved
Bear 1000TbirdBird 8400Sti
• The Respiratory Therapist sets :– pressure limit = plateau seen during
VC– respiratory rate– peak flow rate (the flow if TV < target)– PEEP– FiO2– trigger sensitivity– minimum tidal volume
Dual Control within a Dual Control within a BreathBreath
volume-assured pressure supportvolume-assured pressure support
PPawaw
cmHcmH2200
6060
-20-20
6060
FlowFlowL/minL/min
VolumeVolume
Set flow limit
Set tidal volume cycle threshold
Set pressure limit
Tidal volume met
Tidal volume not met
Switch from Pressure control toVolume/flow control
Inspiratory flowgreater than set flow
Flow cycleInspiratory flowequals set flow
Pressure limitoverridden
LL
0
0.6
4040
Pressure at Pressure support
delivered VT
≥ set VT
flow= 25% peak
Cycle offinspiration
Insp flow> Set flow
PAW <PSVsetting
delivered VT
= set VT
Switch to flow controlat peak flow setting
trigger
yes
no
no
no
no
no
yes
yes
yes
Control logic for volume-assured pressure-support mode
yes
Dual Control within a Dual Control within a BreathBreath
volume-assured pressure supportvolume-assured pressure support• If pressure too high, all breaths are pressure-
limited.• If the peak flow setting is too high , all
breaths will be volume-controlled• If the pressure is set too high or the minimum
tidal volume is set too low; the volume guarantee is negated
• If peak flow set too low, the switch from pressure to volume is late in the breath, inspiratory time is too long.
Dual Control within a Dual Control within a BreathBreath
volume-assured pressure supportvolume-assured pressure support• Amato et al Chest 1992;102: 1225-
1234• Compared VAPS to simple AC
volume– Lower WOB– Lower Raw– Less PEEPi
Dual Control Breath-to-Dual Control Breath-to-BreathBreath
pressure-limited flow-cycled pressure-limited flow-cycled ventilationventilation
Volume SupportVolume Support• Tidal volume is used as feedback Tidal volume is used as feedback control to adjust the pressure support control to adjust the pressure support levellevel
• All breaths are patient triggered, All breaths are patient triggered, pressure limited, and flow-cycled.pressure limited, and flow-cycled.
• Automatic weaning of pressure support as long as tidal volume matches minimum required VT (VT set in a feedback loop to adjust pressure).
Dual Control Breath-to-Dual Control Breath-to-BreathBreath
pressure-limited flow-cycled pressure-limited flow-cycled ventilationventilation
Volume SupportVolume Support
Servo 300 Maquet Servo-i
VS vs VAPSVS vs VAPS
• How does volume support differ from VAPS ?– In volume support, we are trying to
adjust pressure so that, within a few breaths, desired VT is reached.
– In VAPS, we are aiming for desired VT tacked on to the end of a breath if a pressure-limited breath is going to fail to achieve VT
VS (Volume Support)VS (Volume Support)• Entirely a spontaneous modeEntirely a spontaneous mode• Delivers a patient triggered (pressure or flow), pressure Delivers a patient triggered (pressure or flow), pressure
targeted, flow cycled breath targeted, flow cycled breath – Can also be timed cycled (if TI is extended for some reason) or Can also be timed cycled (if TI is extended for some reason) or
pressure cycled (if pressure rises too high).pressure cycled (if pressure rises too high).
• Similar to pressure support except VS also targets set VSimilar to pressure support except VS also targets set VT. T.
It adjusts pressure (up or down) to achieve the set It adjusts pressure (up or down) to achieve the set volume (the maximum pressure change is < 3 cm Hvolume (the maximum pressure change is < 3 cm H22O O and ranges from 0 cm Hand ranges from 0 cm H22O to 5 cm HO to 5 cm H22O below the high O below the high pressure alarm settingpressure alarm setting
• Used for patients ready to be “weaned” from the Used for patients ready to be “weaned” from the ventilator and for patients who cannot do all the WOB but ventilator and for patients who cannot do all the WOB but who are breathing spontaneouslywho are breathing spontaneously
VS (Volume Support)VS (Volume Support)
(1), VS test breath (5 cm H2O); (2), pressure is increased slowly until target volume is achieved; (3), maximum available pressure is 5 cm H2O below upper pressure limit; (4), VT higher than set VT delivered results in lower pressure; (5), patient can trigger breath; (6) if
apnea alarm is detected, ventilator switches to PRVC
Volume fromVentilator=
Set tidal volume
Flow= 5% ofPeak flow
Pressure limitBased on VT/Ctrigger cycle off
calculatecompliance
Calculate newPressure limit
no
yes
yes
no
Control logic for volume support mode of the servo 300
Dual Control Breath-to-Dual Control Breath-to-BreathBreath
pressure-limited flow-cycled pressure-limited flow-cycled ventilationventilation
Volume SupportVolume Support• Little data to show it actually works.• If pressure support level increases to
maintain TV in pt with increased airways resistance, PEEPi may increase.
• If minimum TV set too high, weaning may be delayed.
VS (Volume Support)VS (Volume Support)
• IndicationsIndications• Spontaneous breathing patient Spontaneous breathing patient
who require minimum who require minimum EE• Patients who have inspiratory Patients who have inspiratory
effort who need adaptive supporteffort who need adaptive support• Patients who are asynchronous Patients who are asynchronous
with the ventilatorwith the ventilator• Used for patient who are ready to Used for patient who are ready to
weanwean
VS (Volume Support)VS (Volume Support)
• AdvantagesAdvantages• Guaranteed VGuaranteed VTT and and EE• Pressure supported breaths using the Pressure supported breaths using the
lowest required pressurelowest required pressure• Decreases the patient’s spontaneous Decreases the patient’s spontaneous
respiratory raterespiratory rate• Decreases patient WOBDecreases patient WOB• Allows patient control of I:E timeAllows patient control of I:E time• Breath by breath analysisBreath by breath analysis• Variable Variable II to meet the patient’s demand to meet the patient’s demand
VS (Volume Support)VS (Volume Support)
• DisadvantagesDisadvantages• Spontaneous ventilation requiredSpontaneous ventilation required• VVTT selected may be too large or small selected may be too large or small
for patientfor patient• Varying mean airway pressureVarying mean airway pressure• Auto-PEEP may affect proper Auto-PEEP may affect proper
functioningfunctioning• A sudden increase in respiratory rate A sudden increase in respiratory rate
and demand may result in a decrease and demand may result in a decrease in ventilator supportin ventilator support
Dual Control Breath-to-Dual Control Breath-to-BreathBreath
pressure-limited time-cycled pressure-limited time-cycled ventilationventilation
Pressure Regulated Volume ControlPressure Regulated Volume Control
Servo 300 Maquet Servo-i
Dual Control Breath-to-Dual Control Breath-to-BreathBreath
pressure-limited time-cycled pressure-limited time-cycled ventilationventilation
Pressure Regulated Volume ControlPressure Regulated Volume Control• Delivers patient or timed triggered, Delivers patient or timed triggered,
pressure-targeted (controlled) and time-pressure-targeted (controlled) and time-cycled breathscycled breaths
• Ventilator measures VVentilator measures VTT delivered with delivered with VVT T set on the controls. If delivered Vset on the controls. If delivered VTT is is less or more, ventilator increases or less or more, ventilator increases or decreases pressure delivered until set decreases pressure delivered until set VVTT and delivered V and delivered VT T are equalare equal
Dual Control Breath-to-Dual Control Breath-to-BreathBreath
pressure-limited time-cycled pressure-limited time-cycled ventilationventilation
Pressure Regulated Volume ControlPressure Regulated Volume Control• The ventilator will not allow delivered The ventilator will not allow delivered
pressure to rise higher than 5 cm pressure to rise higher than 5 cm H2O below set upper pressure limitH2O below set upper pressure limit
• Example:Example: If upper pressure limit is set to 35 cm If upper pressure limit is set to 35 cm H2O and the ventilator requires more than 30 cm H2O and the ventilator requires more than 30 cm H2O to deliver a targeted VH2O to deliver a targeted VTT of 500 mL, an alarm of 500 mL, an alarm will sound alerting the clinician that too much will sound alerting the clinician that too much pressure is being required to deliver set volume pressure is being required to deliver set volume (may be due to bronchospasm, secretions, changes (may be due to bronchospasm, secretions, changes in CL, etc.)in CL, etc.)
PRVC (Pressure PRVC (Pressure Regulated Volume Regulated Volume
Control)Control)
PRVC. (1), Test breath (5 cm H2O); (2) pressure is increased to deliver set volume; (3), maximum
available pressure; (4), breath delivered at preset E, at preset f, and during preset TI; (5), when VT
corresponds to set value, pressure remains constant; (6), if preset volume increases, pressure decreases; the ventilator continually monitors and adapts to the patient’s needs
Volume fromVentilator=
Set tidal volume
time= setInspiratory time
Pressure limitBased on VT/Ctrigger cycle off
calculatecompliance
Calculate newPressure limit
no
yes
yes
no
Control logic for pressure-regulated volume control and autoflow
PRVC (Pressure Regulated PRVC (Pressure Regulated Volume Control)Volume Control)
• Disadvantages and RisksDisadvantages and Risks• Varying mean airway pressureVarying mean airway pressure• May cause or worsen auto-PEEPMay cause or worsen auto-PEEP• When patient demand is increased, When patient demand is increased,
pressure level may diminish when pressure level may diminish when support is neededsupport is needed
• May be tolerated poorly in awake non-May be tolerated poorly in awake non-sedated patientssedated patients
• A sudden increase in respiratory rate A sudden increase in respiratory rate and demand may result in a decrease in and demand may result in a decrease in ventilator supportventilator support
PRVC (Pressure Regulated PRVC (Pressure Regulated Volume Control)Volume Control)
• IndicationsIndications• Patient who require the lowest Patient who require the lowest
possible pressure and a possible pressure and a guaranteed consistent VTguaranteed consistent VT
• ALI/ARDSALI/ARDS• Patients requiring high and/or Patients requiring high and/or
variable variable II• Patient with the possibility of CPatient with the possibility of CL L
or Raw changesor Raw changes
PRVC (Pressure Regulated PRVC (Pressure Regulated Volume Control)Volume Control)
• AdvantagesAdvantages• Maintains a minimum PIPMaintains a minimum PIP• Guaranteed VGuaranteed VTT and and EE
• Patient has very little WOB requirementPatient has very little WOB requirement• Allows patient control of respiratory Allows patient control of respiratory
rate and rate and EE• Variable Variable E E to meet patient demandto meet patient demand• Decelerating flow waveform for Decelerating flow waveform for
improved gas distributionimproved gas distribution• Breath by breath analysisBreath by breath analysis
Many Dual Modes start out looking like PCV
A New Twist…A New Twist…Volume TargetedVolume Targeted
1 2 3 4 5 6
SEC
1 2 3 4 5 6
Paw
cmH20
60
-20
120
120
SEC
INSP
EXH
FlowL/min
Volume TargetedVolume Targeted(Pressure Controlled)(Pressure Controlled)
As compliance changes - flow and volumes change
1 2 3 4 5 6
SEC
1 2 3 4 5 6
Paw
cmH20
60
-20
120
120
SEC
INSP
EXH
FlowL/min
Pressure then raises to assure that the set tidal volume is delivered
New Volume Targeted Breath New Volume Targeted Breath Pressure Variability is ControlledPressure Variability is Controlled
1 2 3 4 5 6
SEC
1 2 3 4 5 6
Paw
cmH20
60
-20
120
120
SEC
INSP
EXH
FlowL/min
Dual Control Breath-to-Dual Control Breath-to-BreathBreath
adaptive support ventilationadaptive support ventilation
ASV (Adaptive Support ASV (Adaptive Support Ventilation)Ventilation)
• A dual control mode that uses A dual control mode that uses pressure ventilation (both PC and PSV) pressure ventilation (both PC and PSV) to maintain a set minimum to maintain a set minimum E E (volume (volume target) using the least required target) using the least required settings for minimal WOB depending settings for minimal WOB depending on the patient’s condition and efforton the patient’s condition and effort– It automatically adapts to patient demand It automatically adapts to patient demand
by increasing or decreasing support, by increasing or decreasing support, depending on the patient’s elastic and depending on the patient’s elastic and resistive loadsresistive loads
ASV (Adaptive Support ASV (Adaptive Support Ventilation)Ventilation)
• The clinician enters the patient’s IBW, which allows the The clinician enters the patient’s IBW, which allows the ventilator’s algorithm to choose a requiredventilator’s algorithm to choose a required E. E. The The ventilator then delivers 100 mL/min/kg.ventilator then delivers 100 mL/min/kg.
• A series of test breaths measures the system C, A series of test breaths measures the system C, resistance and auto-PEEPresistance and auto-PEEP
• If no spontaneous effort occurs, the ventilator If no spontaneous effort occurs, the ventilator determines the appropriate respiratory rate,determines the appropriate respiratory rate, V VTT, , and and pressure limit delivered for the mandatory breathspressure limit delivered for the mandatory breaths
• I:E ratio andI:E ratio and T TII of the mandatory breaths are of the mandatory breaths are continually being “optimized” by the ventilator to continually being “optimized” by the ventilator to prevent auto-PEEPprevent auto-PEEP
• If the patient begins having spontaneous breaths, the If the patient begins having spontaneous breaths, the number of mandatory breaths decrease and the number of mandatory breaths decrease and the ventilator switches to PS at the same pressure levelventilator switches to PS at the same pressure level
• Pressure limits for both mandatory and spontaneous Pressure limits for both mandatory and spontaneous breaths are always being automatically adjusted to breaths are always being automatically adjusted to meet the meet the E E targettarget
ASV (Adaptive Support ASV (Adaptive Support Ventilation)Ventilation)
• IndicationsIndications• Full or partial ventilatory supportFull or partial ventilatory support• Patients requiring a lowest possible PIP and a Patients requiring a lowest possible PIP and a
guaranteed Vguaranteed VTT
• ALI/ARDSALI/ARDS• Patient requiring high and/or variable Patient requiring high and/or variable • Patients not breathing spontaneously and not Patients not breathing spontaneously and not
triggering the ventilatortriggering the ventilator• Patient with the possibility of work land Patient with the possibility of work land
changes (Cchanges (CL L and Raw)and Raw)• Facilitates weaningFacilitates weaning
ASV (Adaptive Support ASV (Adaptive Support Ventilation)Ventilation)
• AdvantagesAdvantages– Guaranteed VGuaranteed VTT and and E E
– Minimal patient WOBMinimal patient WOB– Ventilator adapts to the patientVentilator adapts to the patient– Weaning is done automatically and Weaning is done automatically and
continuouslycontinuously– Variable to meet patient demandVariable to meet patient demand– Decelerating flow waveform for improved Decelerating flow waveform for improved
gas distributiongas distribution– Breath by breath analysisBreath by breath analysis
ASV (Adaptive Support ASV (Adaptive Support Ventilation)Ventilation)
• Disadvantages and RisksDisadvantages and Risks• Inability to recognize and adjust to changes in Inability to recognize and adjust to changes in
alveolar Valveolar VDD
• Possible respiratory muscle atrophyPossible respiratory muscle atrophy• Varying mean airway pressureVarying mean airway pressure• In patients with COPD, a longer TIn patients with COPD, a longer TE E may be may be
required required • A sudden increase in respiratory rate and A sudden increase in respiratory rate and
demand may result in a decrease in ventilator demand may result in a decrease in ventilator supportsupport
AutomodeAutomode• The ventilator switch between mandatory and The ventilator switch between mandatory and
spontaneous breathing modesspontaneous breathing modes• Combines volume support (VS) and pressure-Combines volume support (VS) and pressure-
regulated volume control (PRVC)regulated volume control (PRVC)• If patient is paralyzed; the ventilator will provide If patient is paralyzed; the ventilator will provide
PRVC. All breaths are mandatory that are PRVC. All breaths are mandatory that are ventilator triggered, pressure controlled and time ventilator triggered, pressure controlled and time cycled; the pressure is adjusted to maintain the set cycled; the pressure is adjusted to maintain the set tidal volume.tidal volume.
• If the patient breathes spontaneously for two If the patient breathes spontaneously for two consecutive breaths, the ventilator switches to VS. consecutive breaths, the ventilator switches to VS. All breaths are patient triggered, pressure limited, All breaths are patient triggered, pressure limited, and flow cycled.and flow cycled.
• If the patient becomes apneic for 12 seconds; the If the patient becomes apneic for 12 seconds; the ventilator switches back to PRVCventilator switches back to PRVC
MMV (Mandatory MMV (Mandatory Minute Ventilation)Minute Ventilation)• AKA: Minimum Minute Ventilation or AKA: Minimum Minute Ventilation or
Augmented minute ventilationAugmented minute ventilation• Operator sets a minimum Operator sets a minimum E E which usually is which usually is
70% - 90% of patient’s current 70% - 90% of patient’s current E. E. The The ventilator provides whatever part of the ventilator provides whatever part of the E E
that the patient is unable to accomplish. that the patient is unable to accomplish. This accomplished by increasing the breath This accomplished by increasing the breath rate or the preset pressure.rate or the preset pressure.
• It is a form of PSV where the PS level is not It is a form of PSV where the PS level is not set, but rather variable according to the set, but rather variable according to the patient’s needpatient’s need
MMV (Mandatory Minute MMV (Mandatory Minute Ventilation)Ventilation)
• IndicationsIndications– Any patient who is spontaneously and Any patient who is spontaneously and
is deemed ready to weanis deemed ready to wean– Patients with unstable ventilatory drivePatients with unstable ventilatory drive
• AdvantagesAdvantages– Full to partial ventilatory supportFull to partial ventilatory support– Allows spontaneous ventilation with Allows spontaneous ventilation with
safety netsafety net– Patient’s Patient’s E E remains stableremains stable– Prevents hypoventilationPrevents hypoventilation
MMV (Mandatory Minute MMV (Mandatory Minute Ventilation)Ventilation)
• DisadvantagesDisadvantages• An adequate An adequate E E may not equal sufficient may not equal sufficient AA
(e.g., rapid shallow breathing)(e.g., rapid shallow breathing)• The high rate alarm must be set low enough The high rate alarm must be set low enough
to alert clinician of rapid shallow breathingto alert clinician of rapid shallow breathing• Variable mean airway pressureVariable mean airway pressure• An inadequate set An inadequate set EE (>spontaneous (>spontaneous EE) )
can lead to inadequate support and patient can lead to inadequate support and patient fatiguefatigue
• An excessive set An excessive set E E (>spontaneous (>spontaneous EE) with ) with no spontaneous breathing can lead to total no spontaneous breathing can lead to total supportsupport
PAV (Proportional Assist PAV (Proportional Assist Ventilation)Ventilation)
• Provides pressure, flow assist, and Provides pressure, flow assist, and volume assist in proportion to the volume assist in proportion to the patient’s spontaneous effort, the patient’s spontaneous effort, the greater the patient’s effort, the greater the patient’s effort, the higher the flow, volume, and higher the flow, volume, and pressurepressure
• The operator sets the ventilator’s volume The operator sets the ventilator’s volume and flow assist at approximately 80% of and flow assist at approximately 80% of patient’s elastance and resistance. The patient’s elastance and resistance. The ventilator then generates proportional ventilator then generates proportional flow and volume assist to augment the flow and volume assist to augment the patient’s own effortpatient’s own effortDrager Evita
4
PAV (Proportional Assist PAV (Proportional Assist Ventilation)Ventilation)
• IndicationsIndications• Patients who have WOB Patients who have WOB
problems associated with problems associated with worsening lung characteristicsworsening lung characteristics
• Asynchronous patients who are Asynchronous patients who are stable and have an inspiratory stable and have an inspiratory efforteffort
• Ventilator-dependent patients Ventilator-dependent patients with COPDwith COPDDrager Evita 4
PAV (Proportional Assist PAV (Proportional Assist Ventilation)Ventilation)
• AdvantagesAdvantages– The patient controls the ventilatory The patient controls the ventilatory
variables ( variables ( II, PIP, T, PIP, TII, T, TEE, V, VTT))– Trends the changes of ventilatory effort Trends the changes of ventilatory effort
over timeover time– When used with CPAP, inspiratory When used with CPAP, inspiratory
muscle work is near that of a normal muscle work is near that of a normal subject and may decrease or prevent subject and may decrease or prevent muscle atrophymuscle atrophy
– Lowers airway pressureLowers airway pressureDrager Evita 4
PAV (Proportional Assist PAV (Proportional Assist Ventilation)Ventilation)
• DisadvantagesDisadvantages– Patient must have an adequate spontaneous respiratory Patient must have an adequate spontaneous respiratory
drive drive – Variable VVariable VTT and/or PIP and/or PIP– Correct determination of CCorrect determination of CLL and Raw is essential and Raw is essential
(difficult). Both under and over estimates of C(difficult). Both under and over estimates of CLL and Raw and Raw during ventilator setup may significantly impair proper during ventilator setup may significantly impair proper patient-ventilator interaction, which may cause excessive patient-ventilator interaction, which may cause excessive assist (“Runaway”) – the pressure output from the assist (“Runaway”) – the pressure output from the ventilator can exceed the pressure needed to overcome ventilator can exceed the pressure needed to overcome the system impedance (Cthe system impedance (CLL and Raw) and Raw)
– Air leak could cause excessive assist or automatic cyclingAir leak could cause excessive assist or automatic cycling– Trigger effort may increase with auto-PEEPTrigger effort may increase with auto-PEEP
What is BiLevel What is BiLevel Ventilation?Ventilation?
• Is a spontaneous breathing mode in which two levels Is a spontaneous breathing mode in which two levels of pressure and hi/low are setof pressure and hi/low are set
• Enabled utilizing an active exhalation valveEnabled utilizing an active exhalation valve• Substantial improvements for spontaneous breathingSubstantial improvements for spontaneous breathing
– better synchronization, more options for supporting better synchronization, more options for supporting spontaneous breathing, and potential for improved spontaneous breathing, and potential for improved monitoringmonitoring
BiLevel VentilationBiLevel Ventilation
Synchronized TransitionsSpontaneous Breaths
Spontaneous Breaths
PPawaw
cmHcmH2200
6060
-20-201 2 3 4 5 6 7
What is BiLevel What is BiLevel Ventilation?Ventilation?
• At either pressure level the patient can At either pressure level the patient can breathe spontaneouslybreathe spontaneously– spontaneous breaths may be supported by PS spontaneous breaths may be supported by PS
– if PS is set higher than PEEPif PS is set higher than PEEPHH, PS supports , PS supports spontaneous breath at upper pressure spontaneous breath at upper pressure
BiLevel VentilationBiLevel Ventilation
PEEPPEEPHH
PEEPPEEPLL
Pressure SupportPressure SupportPEEPPEEPHigh High + PS + PS
PPawaw
cmHcmH2200
6060
-20-201 2 3 4 5 6 7
Then What Is APRV?Then What Is APRV?
• Is a Bi-level form of ventilation with sudden short releases in Is a Bi-level form of ventilation with sudden short releases in pressure to rapidly reduce FRC and allow for ventilationpressure to rapidly reduce FRC and allow for ventilation
• Can work in spontaneous or apneic patients Can work in spontaneous or apneic patients • APRV is similar but utilizes a very short expiratory time for APRV is similar but utilizes a very short expiratory time for
PRESSURE RELEASEPRESSURE RELEASE– this short time at low pressure allows for ventilationthis short time at low pressure allows for ventilation
• APRV always implies an inverse I:E ratioAPRV always implies an inverse I:E ratio
• All spontaneous breathing is done at upper pressure levelAll spontaneous breathing is done at upper pressure level
APRV (Airway Pressure APRV (Airway Pressure Release Ventilation)Release Ventilation)
• Provides two levels of CPAP and allows Provides two levels of CPAP and allows spontaneous breathing at both levels when spontaneous breathing at both levels when spontaneous effort is presentspontaneous effort is present
• Both pressure levels are time triggered and Both pressure levels are time triggered and time cycledtime cycled
APRV (Airway Pressure APRV (Airway Pressure Release Ventilation)Release Ventilation)
• Allows spontaneously breathing patients to Allows spontaneously breathing patients to breathe at a high CPAP level, but drops breathe at a high CPAP level, but drops briefly (approximately 1 second) and briefly (approximately 1 second) and periodically to allow CPAP level for extra periodically to allow CPAP level for extra CO2 elimination (airway pressure release)CO2 elimination (airway pressure release)
• Mandatory breaths occur when the pressure Mandatory breaths occur when the pressure limit rises from the lower CPAP to the limit rises from the lower CPAP to the higher CPAP levelhigher CPAP level
APRV (Airway Pressure APRV (Airway Pressure Release Ventilation)Release Ventilation)
• IndicationsIndications• Partial to full ventilatory supportPartial to full ventilatory support• Patients with ALI/ARDSPatients with ALI/ARDS• Patients with refractory Patients with refractory
hypoxemia due to collapsed hypoxemia due to collapsed alveolialveoli
• Patients with massive atelectasisPatients with massive atelectasis• May use with mild or no lung May use with mild or no lung
diseasedisease
APRV (Airway Pressure APRV (Airway Pressure Release Ventilation)Release Ventilation)
• AdvantagesAdvantages• Allows inverse ratio ventilation (IRV) with or without Allows inverse ratio ventilation (IRV) with or without
spontaneous breathing (less need for sedation or spontaneous breathing (less need for sedation or paralysis)paralysis)
• Improves patient-ventilator synchrony if spontaneous Improves patient-ventilator synchrony if spontaneous breathing is presentbreathing is present
• Improves mean airway pressureImproves mean airway pressure• Improves oxygenation by stabilizing collapsed alveoliImproves oxygenation by stabilizing collapsed alveoli• Allows patients to breath spontaneously while Allows patients to breath spontaneously while
continuing lung recruitmentcontinuing lung recruitment• Lowers PIPLowers PIP• May decrease physiologic deadspaceMay decrease physiologic deadspace
APRV (Airway Pressure APRV (Airway Pressure Release Ventilation)Release Ventilation)
• Disadvantages and RisksDisadvantages and Risks• Variable VTVariable VT• Could be harmful to patients with high Could be harmful to patients with high
expiratory resistance (i.e., COPD or asthma)expiratory resistance (i.e., COPD or asthma)• Auto-PEEP is usually presentAuto-PEEP is usually present• Caution should be used with Caution should be used with
hemodynamically unstable patientshemodynamically unstable patients• Asynchrony can occur is spontaneous Asynchrony can occur is spontaneous
breaths are out of sync with release timebreaths are out of sync with release time• Requires the presence of an “active Requires the presence of an “active
exhalation valve”exhalation valve”
Airway Pressure Release Airway Pressure Release VentilationVentilation
PPawaw
cmHcmH2200
6060
-20-201 2 3 4 5 6 7 8
Spontaneous Breaths
Releases