This document discusses various dual control modes of mechanical ventilation that switch between pressure control and volume control within or between breaths based on measured patient characteristics. It describes the advantages of volume control and pressure control modes individually. It then explains different types of dual control modes including dual control within a breath (e.g. Volume-assured Pressure Support), dual control breath-to-breath where the ventilator adjusts pressure to ensure tidal volume delivery, and combination modes. Key aspects of settings and operation are outlined for different dual control modes.

1. DUAL CONTROLLED MODES OFMECHANICAL VENTILATION
Dual control modeshave beendevelopedtoprovide the benefitsof bothvolume control and
pressure control ventilation:
Advantage of Volume control modes:
- Guarantee a presettidal volume andminuteventilation
Advantage of Pressure control modes:
- The abilitiytodetermineandmaintainpeakairwaypressureandinspiratorytime
- The variable anddeceleratinginspiratoryflow pattern
Dual control modesare closed-loopsystemsthatswitchbetweenpressure control andvolume
control in a single breathorbreathto breathon measuredpatientcharacteristics.Dual control
modeschange the output(pressure) basedonameasuredinput(volume). The dual-control modes
can be patient-triggeredortime-triggered,andflow-cycledortime-cycled.
I. Dual control withinabreath modes
Volume-assuredPS(VAPS): Bird8400 STi,TBird,Avea
Pressure Augmentation(PA):Bear1000
II.Dual control breathto breathmodes
Pressure limited,Flowcycled:
Volume support(VSV):Servo300
Variable PS:Venturi
Pressure limited,Timecycled:
Pressure RegulatedVolume Control (PRVC):Servo300
Autoflow:Evita4
Variable Pressure Control:Venturi
Volume Control Plus:PuritanBennett840
Adaptive PS:Gallileo
III.CombinationModes
Adaptive Supportventilation:Gallileo

2. Automode:Servo300
Dual control withinabreath
- Volume assuredpressure support(VAPS)
- Pressure augmentation(PA)
The ventilatorswitchesfromPCorPS to VCduringthe inspiratoryphase of individualbreathsbased
on the patient’sinspiratoryeffortandabilitytoachieve the clinicansetminimumtidal volume
Thistechnique combinesthe highinitial flowof pressure limitedbreathwithpossibilityof switching
to constantflow(volume limitedbreath).
The advantage of dual control withina breathis reducedworkof breathingwhile maintaininga
minimumguaranteedtidalvolumeandminute ventilation.
Once the breath triggered(patientortime) the ventilatorattemptstoreachthe pressure support
settingasquicklyaspossible.Thisportionof breathisthe pressure limitedportionandassociated
witha highvariable flow.
As the pressure support levelisreached,the ventilatormeasuresdeliveredflow andvolume and
starts a continuouscomparisonbetweenthe volumethathasbeendeliveredandthe desiredtidal
volume.
If the deliveredtidal volumeandsettidal volume are equal,the breathisapressure supportbreath
If the deliveredtidal volumeremainsgreaterthanthe setminimum, the ventilatoroperatesinthe
pressure supportmode andmakesnomaniplations.
If the micropressorfindsthatthe measuredflowisinadequte toachieve the settidal volume inthe
setinspiratorytime,inspirationcontinuesaccordingtothe peakflow settinguntil the set minimum
tidal volume hasbeendelivered;thatisthe breathchangesfrom pressure limitedtovolumelimited.
In thissituation,airwaypressurewillrise above the setpressuresupportlevel.If inspiratorytime
longerthan3 seconds,breathwill be automaticallytimecycled.
Because of the airwaypressure mayrise above the setpressure supportsettingduringthe volume
limitedportionof the breath,the highpressure alarmisimportant.
Choosingthe appropriate pressureandflow settingsiscritical
- If the pressure issettoohighand minimumtidal volume issetlow all breathswill be
pressure supportbreathsandminimumtidal volume guarantee will be providedwithoutany
feedbackoperation.
- If the peakflowissettoo low,the switchfrompressure tovolume willoccurlate and
inspiratorytime maybe prolonged.
- PS setting

3. - PSsettingat a level equivalanttothe plateaupressure obtainedduringavolume control
breathat a desiredtidal volume canbe used
- Peakflowsetting
- Peakflowshouldbe adjustedtoallow forthe appropriate inspiratorytime andinspiratory
to expiratoryratiorequiredbythe patient
Dual control breathto breathmodes
Pressure limited,Flowcycled:Volumesupport(VSV),Variable PS
These modesare closedloopcontrol of pressure support ventilation.Tidal volume isusedasa
feedbackcontrol forcontiniouslyadjustingthe pressure supportlevel.
The peak pressure isadjustedtoensure deliveryof the targettidal volume basedonthe compliance
measuredduringthe previousbreath.
Dual control breathto breathmodes;Pressure limited,Flowcycled
VSV
A test breathisdeliveredwith aninspiratorypressure of 10 cmH2Oabove PEEP and ventilator
measuresdeliveredtidal volume andcalculatesthe total systemcompliance.The followingthree
breathsare deliveredatapeakpressure of 75% of the pressure thatcalculatedtodeliverthe
minimumsettidal volume.
All breathsare patienttriggered,pressurelimitedandflow cycledpressuresupportbreaths
The maximumpressure change breathtobreathis≤3 cmH2O and can range from0 cmH2O above
PEEP to 5 cmH2O belowhighpressure alarmsetting.
Respiratoryfrequency,inspiratorytimeandflow are determinesbythe patient.
If inspiratorytime exceeds80%of the total cycle time a secondarycyclingmechanismisactivated.
Decrease inpatientrespiratoryfrequencycausesautomaticallyincrease inthe tidal volumetargetto
maintainthe minute volumeconstant
Settingalarmsforminute ventilation,highpressureandrespiratoryrate isimportantforsafelyusing
these modes
Increasesinpressure level tomaintainthe tidal volume mayincrease autoPEEPatthe patientswho
has airflowobstruction.
As the autoPEEPincreasesthe same pressure resultsinasmallertidal volume.Inthissituation,the
algorithymincreasesthe pressure limit,increasingthe pressure worsensairtrapping.

4. Thisviciouscircle of increasingpressure support,worseningairtrappingcausestoinabilitytotrigger
the ventilator.Decreasinginrespiratoryrate resultsinfurtherincrease intidal volume tomaintain
the same minute volume.
In casesof hyperpneaventialtordecreasespressuresupport.If the cause of hyperpneaisincrease in
metabolicdemand,decreasingthe pressure supportlevel isopposite response.
The inabilityof all dual modestodistinguishbetweenimprovedpulmonarycomplianceabdincreased
patienteffort(increasedmetabolicdemand)
These modesallowautomaticreductionof pressure supportaslungmechanicsimproveandpatient
effortincreases
These modescanbe usedasa weaningmode byclinicianreductionof the targettidal volume
If the cliniciansetsminimumtidal volume greaterthanthe patientdemand,the patientmayremain
at that level of supportandweaningmaybe delayed.
Dual control breathto breathmodes:Pressure limited,Time cycled
Pressure RegulatedVolume Control,Autoflow,Variable Pressure Control,Volume ControlPlus,
Adaptive PS
These modesare closedloopcontrol of pressure control ventilation.The pressurelimitisadjusted
usingthe cliniciansetdesiredtidal volumasthe negativefeedbackcontrol.
The primaryadvantage of these modesisreductioninpeakinspiratorypressureassociatedwitha
decleratingflow pattern,combinedwiththe guaranteeddeliveryof minutevolum.
These modesenable the ventilatortoadjustinspiratoryflowaccordingtopatientflow demand
combinedwithmaintenance of constanttidal volum.
All breathsinthese modesare time orpatienttriggered,pressure limitedandtime cycled.
These modesallowdual control breathtobreathbyusingeithercontinuousmandatoryventilation
or SIMV exceptPRVCthatallowscontinuousmandatoryventilation.
DuringSIMV the mandatorybreathsare the dual control breaths
PRVC
The pressure limit fluctuatesbetween0cmH2O above PEEPlevel to5 cmH2O below the upper
pressure alarmlimit.
Upper pressure alarmlimitiscritic.If the desiredtidal volumisnotdeliveredwiththe pressure of 5
cmH2O belowthe upperpressure alarmlimit,the ventilatorwillalarm.
Hipoventilationmayoccurif the desiredtidal volume andmaximumpressure alarmlimitsettingsare
incompatible

5. CombinationModes
Adaptive Supportventilation,Automode
Automode
Automode designedforautomatedweaningfrompressure control topressure supportandfor
automatedescalationof supportif patientefortdiminishesbelow aselectedthreshold.
It combinesvolumesupportventilationandPRVCintoa single mode;Thismode providesa
continuousweaningfrompressure control to pressure supportorfromvolume control tovolume
supportwithguaranteedtidal volum
Automode
The ventilatorprovidesPRVCbreathsif the patientisparalyzed.Allbreathsare mandatory,time
triggered,pressure limitedandtime cycled.The pressure limitincreasesordecreasestomaintainthe
desiredtidal volum.
If the patienttriggers2 consecutive breaths,the ventilatorswitchestovolume support.Inthiscase,
all breathsare patienttriggered,pressure limitedandflow cycled.
If the patientbecomesapneicfor12 seconds(8 secondsforpediatric,5secondsforneonatal
patient) the ventilatorswitchestoPRVC.
The switchesPRVCtoVSare accomplishedatequivalantpeakpressure.
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