Newer modes ofNewer modes ofMechanical Mechanical VentilationVentilation

Dr. T.R. ChandrashekarDr. T.R. ChandrashekarDirector Critical Care Director Critical Care

K.R.HospitalK.R.HospitalBangaloreBangalore

Outline of the talkOutline of the talk Which modes qualify as newer modes?Which modes qualify as newer modes? Why newer modes were introduced ?Why newer modes were introduced ?

Let us conceptualise the newer Let us conceptualise the newer modes modes

My classification of newer modesMy classification of newer modes Do we require them? Evidence base Do we require them? Evidence base A few important modes- I will discussA few important modes- I will discuss VAPS, PAV+, APRV/BIPAP, SmartcareVAPS, PAV+, APRV/BIPAP, Smartcare

SIMV

PCV

ACV

CMV

Basic Modes?

PS

Newer [Alternative] Modes?

Volume support (VS)Volume Assured Pressure Support (VAPS)

Pressure regulated volume control ventilation (PRVC)Mandatory minute ventilation (MMV)

PROPORTIONAL ASSIST VENTILATION(PAV)ADAPTIVE SUPPORT VENTILATION(ASV)Smartcare/Automatic tube Compensation

BIPAP/DUOPAPAirway pressure release ventilation (APRV )

High Frequency Ventilation/oscillationPartial Liquid Ventilation (Perflurocarbon)

Neurally Adjusted Ventilatory Assist (NAVA) Fractal ventilation

What are Physicians Doing?

1,638 patients in 412 ICUs

47% Assist-Control Ventilation

46% Pressure Support and/or SIMV

7% Other

Variability in modes across nations

No variability in settings

Esteban et al, AJRCCM 2000; 161:1450-8

0

5

10

15

20

25

30

35

40

Modes of Ventilation during Weaning

Esteban et al, AJRCCM 2000;161:1450

PSSIM

V +PS

Intermittent

SB trials

OthersSIM

VDaily SB

trials

Num

ber

of v

entil

ated

pat

ient

s, (

%)

Why New Modes?

Address important clinical issues: Poor trigger Proportional assist to match patients

effort Improve patient - ventilator synchrony! More rapid weaning! Less likelihood of VILI Less hemodynamic compromise More effectively ventilate/oxygenate!

Satisfies our craving for adventure -(engineers and clinicians) We like better numbers - (seduction by pulse oximetry)

Why newer modes were introduced ?Why newer modes were introduced ?

Let us conceptualise the newer Let us conceptualise the newer modesmodes

Nearly 50% time is spend on weaning

Striving for better outcomes:

The three

• Spontaneous breathing (Girard 2008; MacIntyre 2000, Levine 2008)

• Synchrony (Chao 1997;Thille 2006; De Wit 2009)

• Sedation management (Kress 2000, Girard 2008, De Wit 2009)

All reduce time on mechanical ventilation

Phases of ventilatory Phases of ventilatory cyclecycle

Delay, Missed breaths Fatigue/VIDD/runaway

Old modes trigger delayOld modes trigger delay

Trigger in conventional Trigger in conventional modesmodes

We are targeting the last part of the cycle and Also add the delay from the Y piece or

the machine endTrigger delay is inbuilt in the old modes

We are targeting the last part of the cycle and Also add the delay from the Y piece or

the machine endTrigger delay is inbuilt in the old modes

12

Esophagus

NAVANAVA

Sinderby et al, Nature Med 1999;5:1433

Time (s)0 1 432 0 1 432

Airway Pressure Trigger

Onset of diaphragmatic electrical activityOnset of ventilator flow

Neural Trigger

0

20

-5.0

0.0

0.0

0.5

-1

0

1

Flo

w(l/

s)V

olu

me

(l)P

es

(cm

H2O

)

Pa

w

(cm

H2O

)

Missed breaths

PAV+ vs. PCV /PSV example

PCV

15 cmH2O

PAV+

at 75%

P

T

P

T

P

T

P

T

P

T

P

T

Compared to PCV, the PAV+ mode better matches patient’s effort to ventilator output.

PAV+

Proportional support has synchronised inspiration to expiration cycling

Increase support Sedate

These can lead to disuse atrophy of the respiratory muscles (VIDD) or lowering of the CO2 set point.

Either case can delay weaning and result in more ventilator days!

or

M Younes. Proportional Assist Ventilation, A New Approach to Ventilatory Support. Theory. Am Rev Respir Dis 1992;145:114-120.

The practitioner’s typical The practitioner’s typical response to an increase in response to an increase in

demand is what?demand is what?

we need to select a level of pressure support that is “not too low, not too high, but just right”.Proportional support to patients effort

which can change from breath to breath is ideal

Proportional support is Proportional support is vitalvital

No Diaphragm activity

Missed breaths

Possibly to much pressure support which had suppressed the diaphragmatic activity

Increase the PSIncrease the PS

Automated mechanical ventilation is the future

A growing number of medical errors in the literature related to Workload Due to the shortage of personnel High frequency of severe ‘burnout

syndrome’ among physicians and nurses working in ICUs.

High frequency of staff turnover

Automated mechanical ventilation is the future

In the study by Donchin et al, Average number of activities per patient per day was 178 Activities related to breathing were the most frequent (26% of all activities) An estimated mean number of errors per patient per day

was 1.7 Errors related to breathing were the second most frequent (23% of all errors), after errors related to data entry

The Future of Mechanical The Future of Mechanical VentilationVentilation

What is a Closed Loop VentilationWhat is a Closed Loop Ventilation ??

Automated mechanical ventilation is the future

Advanced closed-loop systems -Reduce the staff workload and to reduce the duration of MV

Closed Loop VentilationClosed Loop Ventilation

Ventilator

Patient

Clinician

Open Loop Open Loop VentilationVentilation

Basic modes-PS/SIMV/CMVSet volume/presuure/flowPatient has to adapt to the ventilator

Gets feedback on lung resistance/compliance

Adapts to the patient- ASV/PAV+/NAVA

Smartcare Intensivists

brain

My classification of new My classification of new MODESMODES

Dual modesDual modes Which combine Volume mode + Pressure Which combine Volume mode + Pressure

modes-modes- VS, MMV, VAPS, PRVC etc…VS, MMV, VAPS, PRVC etc… Modes which adapt to lung characteristicsModes which adapt to lung characteristics ( Resistance & Compliance) PAV+, ASV( Resistance & Compliance) PAV+, ASV Spontaneous breathing + higher FRC-Spontaneous breathing + higher FRC- APRV/ APRV/

BIPAPBIPAP Knowledge based Weaning modes-Knowledge based Weaning modes-

Smartcare, ATC, PAV, ASV, NAVASmartcare, ATC, PAV, ASV, NAVA Better trigger mechanism-Better trigger mechanism- NAVA NAVA

Arguments Against New Arguments Against New ModesModes

Lack high-level evidence for better patient Lack high-level evidence for better patient outcomesoutcomes

If we try a new mode and the patient has a good If we try a new mode and the patient has a good outcome, we say it was due to the new mode.outcome, we say it was due to the new mode.

But if try a new mode and there is a bad But if try a new mode and there is a bad outcome, we say the patient was going to die outcome, we say the patient was going to die anyway.anyway.

Potential for harm Potential for harm (these are often not reported)(these are often not reported) Improved gas exchange does not necessarily Improved gas exchange does not necessarily

improveimprove

outcomes: high tidal volume, iNO, proneoutcomes: high tidal volume, iNO, prone New is New is not not necessarily betternecessarily better Solution to a problem or Solution to a problem or in search of a problem?in search of a problem?

Better oxygenation, faster Better oxygenation, faster weaning, lesser sedation, weaning, lesser sedation, less Asynchrony YES- BUT less Asynchrony YES- BUT

mortality benefit not provedmortality benefit not proved Dual modesDual modes most popular but no great evidence most popular but no great evidence BIPAPBIPAP no great evidence no great evidence NAVANAVA-emerging evidence even in children and -emerging evidence even in children and

NIVNIV ASV- ASV- physiological mode –accumulating physiological mode –accumulating

evidence (ARDS/COPD)evidence (ARDS/COPD) PAVPAV+-better than PAV, physiological mode –+-better than PAV, physiological mode –

accumulating evidence, NIV good evidenceaccumulating evidence, NIV good evidence SmartcarSmartcare-unique mode can say ventilator has e-unique mode can say ventilator has

intensivist’s brain-good evidence for weaningintensivist’s brain-good evidence for weaning

I will discuss these I will discuss these modesmodes

Dual modes-Dual modes-VAPSVAPS – – PAV+,PAV+, BIPAPBIPAP SmartcareSmartcare

VS/PRVC/MMR/MMV etc..VS/PRVC/MMR/MMV etc..

ASVASV

/APRV/APRV

/ ATC/NAVA/ ATC/NAVA

DUAL MODESDUAL MODES

Lung Compliance Changes Lung Compliance Changes and the P-V Loopand the P-V Loop

Lung Compliance Changes Lung Compliance Changes and the P-V Loopand the P-V Loop

Volume (mL)Volume (mL)

PIP levels

Preset VT

PPawaw (cm H (cm H22O)O)

Volume Targeted Ventilation

COMPLIANCEIncreasedNormalDecreased

COMPLIANCEIncreasedNormalDecreased

Volume Control : good and bad

Guaranteed tidal volume- even with variable compliance and resistance.

Less atelectasis compared to pressure control.

Can cause excessive airway pressure-VILI The limited flow available may not meet

the patient’s desired inspiratory flow rate-asynchrony

Leaks = Volume lossLeaks = Volume loss

Lung Compliance Changes Lung Compliance Changes and the P-V Loopand the P-V Loop

Lung Compliance Changes Lung Compliance Changes and the P-V Loopand the P-V Loop

Volume (mL)Volume (mL)

Preset PIP

VT

levels

PPawaw (cm H (cm H22O)O)

COMPLIANCEIncreasedNormalDecreased

COMPLIANCEIncreasedNormalDecreased

Pre

ssu

re T

arg

ete

d

Ven

tilatio

n

Pressure Control :good and bad

• Limits excessive airway pressure• Improves gas distribution

• Less VT as pulmonary mechanics change-atelectasis

• Potentially excessive VT as compliance improves

1.Set Tidal Volume

With

2. Safer Pressure Limit

TargetTarget

PPawaw

cmHcmH2200

6060

-20-20

6060

FlowFlowL/minL/min

VolumeVolume

Set tidal volume cycle threshold

Set pressure limit

Tidal volume met

Tidal volume not met

Switch from Pressure control toVolume control

Flow cycle

LL

0

0.6

4040

VAPS-Volume assured Pressure SupportNormal PS

If Compliance decreases

Dual ModesDual Modes

Volume target achieved-can target a Volume target achieved-can target a pressure limitpressure limit

Issues not addressedIssues not addressed Trigger delayTrigger delay Proportional support-VIDD/fatigueProportional support-VIDD/fatigue Not taking into account lung Not taking into account lung

mechanic’s resistance/compliancemechanic’s resistance/compliance Not physiological -asynchronyNot physiological -asynchrony

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 effort

PAV+ uses the compliance and resistance information collected every 4-10 breaths to know what it’s fighting against.

PAV+ uses the flow and volume information collected every 5 milliseconds to know what the patient wants.

PAV+ combines this data with the %Supp information input by the clinician to determine how much pressure to supply to the system.

PAV+

V.

The clinician will NOT set a rate, tidal volume, flow or target pressure. Instead, the clinician will simply set the percentage of work that the ventilator should do.

f Vt Pi %Suppx x xx

PAV+

PAV+

Start patients at 70% and wean back to stabilize

When disease process has sufficiently reversed, decrease %Support over 2 hr intervals

PAV+ Potential Benefits1. Comfort.

2. Lower peak airway pressure.

3. Less need for paralysis and/or sedation.

4. Less likelihood for over ventilation.

5. Preservation and enhancement of patient’s own control mechanisms such as metabolic ABG control and Hering-Breuer reflex.

Some patients have a high rate normally, so a high rate on PAV+ may or may not reflect distress; check other signs; Try increasing assist to see if rate goes downDon’t be surprised if RR climbs when switching from other modes

1.Circuit MUST be free of large leaks (small leaks are okay).

2.No external nebulizers which add flow.

PAV+ Limitations

PAV+ is NOT recommended for…

1.Low Respiratory drive

2.Abnormal breathing pattern

3.Extreme air trapping

4.Large mechanical leaks.

APRV/BIPAPAPRV/BIPAP Maintain high FRC-better oxygenationMaintain high FRC-better oxygenation Lung in safe zone-less de-recruitment /VILILung in safe zone-less de-recruitment /VILI Spontaneous breaths- diaphragm is active Spontaneous breaths- diaphragm is active

hence less VIDD/better Hemodynamicshence less VIDD/better Hemodynamics Less sedation and analgesia? Conflicting Less sedation and analgesia? Conflicting

resultsresults APRV is IRV hence more impetus on APRV is IRV hence more impetus on

Oxygenation/ synchrony problems persistOxygenation/ synchrony problems persist BIPAP- less synchrony problemsBIPAP- less synchrony problems

Keeps the lung in lung protective zone

APRV settingsAPRV settings

Paw

Thigh (4-5) SecTlow

Phigh

Plow( 1 sec)

Time-triggered, Time-cycled,Pressure-limited,Spontaneous breathing is allowed at any point during the ventilatory cycle

FLOW

Phigh -This parameter is set with the goal of improving oxygenation.Plow -The setting of this parameter has the goal of facilitating ventilation or CO2 clearance.It is this inverse inspiratory:expiratory (I:E) ratio that distinguishes APRV from bi-level positive airway pressure (BiPAP=1:1)

P

T

Synchronized Transitions

PEEPHIGH

PEEPLOW

TLOW

THIGH

Synchronized Transitions

BiLevel Ventilation:BiLevel Ventilation: Uses 2 pressure levels for 2 time periodsUses 2 pressure levels for 2 time periods PEEPPEEPlowlow & PEEP & PEEPhighhigh, T, Thighhigh and T and Tlow low

Patient triggering & cyclingPatient triggering & cycling can change phases can change phases If PS is set higher than PEEPIf PS is set higher than PEEPHH, the PS pressure , the PS pressure

is applied to a spontaneous effort at upper is applied to a spontaneous effort at upper pressurepressure

PEEPHigh + PS

P

PEEPL

PEEPH

Pressure Support

Spontaneous Breaths

P Pressure Support

T

If set PS < than Phigh then only applied in the lower pressure level

If PS> than P-High,Then spontaneous breaths at both levels will be supported

by PS

Smartcare/NeoGaneshSmartcare/NeoGanesh

Complete Closed LoopComplete Closed Loop

The “Zone of Respiratory The “Zone of Respiratory Comfort” or “ZoRC”Comfort” or “ZoRC”

The 3 monitored parameters:

• spontaneous breath rate, fspn• spontaneous tidal volume, VT• etCO2 “ZoRC”-Goals:

1.Regulate Pressure Support to stabilize the

patient within their ZoRC

2) Reduce PS stepwise (in steps of 2 to 4 cmsH2oin steps of 2 to 4 cmsH2o))

to no support, keeping the patient within their

ZoRC.

3) Conduct a Spontaneous Breathing Trial with

no support; if patient remains within ZoRC,

recommend separation from ventilator.

SmartcareSmartcare

These therapeutic measures are These therapeutic measures are based on a clinical protocol based on a clinical protocol that has that has been tested and verified during been tested and verified during several years of developmentseveral years of development....

SmartCare/PS the clinical SmartCare/PS the clinical evidenceevidence

In February 2008, the FDA gave In February 2008, the FDA gave clearance for additional claims of clearance for additional claims of efficacy SmartCare can efficacy SmartCare can

Reduce overall ventilation time by 33%Reduce overall ventilation time by 33% Decrease ICU length of stay by up to Decrease ICU length of stay by up to

20%20% Reduce weaning duration by up to 40%Reduce weaning duration by up to 40%

New Modes of New Modes of Mechanical Ventilation: Mechanical Ventilation:

SummarySummary Older modes & ventilators:Older modes & ventilators:

passive, operator-dependant toolspassive, operator-dependant tools New modes on new generation New modes on new generation

ventilators:ventilators: adaptively interactive to patientadaptively interactive to patient goal orientedgoal oriented Low operator activityLow operator activity

Adapted from John J. Marini, MD; AARC congress, 11/98Adapted from John J. Marini, MD; AARC congress, 11/98

The Evidence for New VentilatorModes …

It’s not the ventilator mode that makes a difference …

… It’s the skills of the clinician that makes the difference.

Any ventilator mode has the potential to do harm! High level evidence is lacking that any new

ventilator mode improves patient outcomes compared to

existing lung-protective ventilation strategies.

Dean Hess

Thank youThank you

Innovation and Automation is the future

PAV+ 80% with varying DemandPAV+ 80% with varying Demand

Patient WorkMachine Work

Amplification of Patient EffortAmplification of Patient Effort

• • Small at low levels and high at high levelsSmall at low levels and high at high levels

• • 20% Support-1.25:120% Support-1.25:1

• • 50% Support -2:1ratio 50% Support -2:1ratio

• • 95% Support 20:195% Support 20:1

Equation of Motion Equation of Motion for the respiratory systemfor the respiratory system

Paw + Pmus = V’ x R + Paw + Pmus = V’ x R + V x EV x E

Ventilator output :Triggering, Cycling

Control of flow, rise time and pressure

MechanicalPatient response Chemical

ReflexBehavioral

Goal 2: Three-knob ventilationGoal 2: Three-knob ventilationWhat is ASV?What is ASV?

Tp

Rate

Psup

PinspTi

Te @

FiO2

PEEP

Vt

CMVSIMVPCV

PSV

ConventionalConventional ASVASV

How do I apply How do I apply ASV?ASV?

Ideal Body WeightIdeal Body WeightYouYou

% Minute Volume% Minute Volume

Ideal Body WeightIdeal Body Weight

How do I apply How do I apply ASV?ASV?

Test breathsTest breathsYouYou

% Minute Volume% Minute Volume

Ideal Body WeightIdeal Body Weight

Automatically applies 3 test Automatically applies 3 test breaths to determine lung breaths to determine lung characteristicscharacteristics

ASVASV