New Modes of Mechanical Ventilation Mazen Kherallah, MD, FCCP Consultant Intensivist King Faisal Specialist Hospital

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

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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


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


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


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


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.


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).



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



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.


• 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


• 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


• 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


pressure-limited time-cycled pressure-limited time-cycled ventilationventilation

Pressure Regulated Volume ControlPressure Regulated Volume Control

Servo 300 Maquet Servo-i



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



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


• 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


• 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


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


• 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


• 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


• 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


• 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


• 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


• 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


• 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

BiLevelsBiLevels

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

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6060

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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

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6060

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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


• 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


• 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


• 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


• 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

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Spontaneous Breaths

Releases

Modes of VentilationModes of Ventilation

• Questions?Questions?

Documents

New Modes of Mechanical Ventilation Mazen Kherallah, MD, FCCP Consultant Intensivist King Faisal Specialist Hospital