MECHANICAL VENTILATION
MECHANICALVENTILATIONAmirali Nader, MD FCCPCritical Care MedicineSuburban HospitalJohns Hopkins Medicine
Mechanical Ventilation: Schedule History, Concepts and Basic Physiology – NaderVolume Control Ventilation (CMV, ACV) – NaderIntermittent Mandatory Ventilation (SIMV) – NaderPressure Support Ventilation (PSV) – NaderPressure Control Ventilation (PCV) – JunkerPressure Regulated Volume Control (PRVC) – JunkerAirway Pressure Release Ventilation (APRV) – JunkerNeurally Adjusted Ventilatory Assist (NAVA) – Nader
1500 Fire BellowParacelsusConcept of ArtificialVentilation1750 Mouth--toMouthto--mouth1908"If you take a dead animal andblow air through its larynx,you will fill its bronchi andwatch its lungs attain thegreatest distention."GalenVesalius
The Drager Pulmotor1911“Artificial Breathing Device”
The Drager Pulmotor used by Fire andPolice Units
1900-1950Iron Lung1927Philip Drinker
Rancho Los Amigos Hospital, 1953
Era of Respiratory Intensive Care1950--19701950 Bird Mark 7Bennet PR2Hamilton StandardBear
ThenNow
Role of Mechanical Ventilation: Provide oxygenation andventilatory support duringrespiratory failureImprove gas exchangeUnload respiratory muscles“Buy time” for healing andrecovery
1950Controlled MVControl/AssistAssistCombinedSIMVPEEPPressure SupportVolume SupportAPRV, BiPAP,AutomodeComplex Algorithms2011NAVAPAVASVOther
Mechanical Ventilation:Positive PressureInvasiveCMV, ACSIMVPS / PCAPRV / BiBi-levelPAV, ASV, NAVANegative PressureNon--InvasiveNonThe Iron LungBiPAPCPAP
A Double-Edged Sword
Hypotension postinduction Hypertension due toagitation, pain,stimulation Hypercapnea cerebral vasodilation Hypoxemia,Acidosis, PEEPComplications of Endotracheal Intubation
Ideal TechnologyCNSPhrenic nerveVentilatorDiaphragm excitationDiaphragm contractionChest wall, lung and esophageal responseflow, pressure,volume changesCurrent Technology
Breath characteristicsTrigger: what initiates a breathTrigger: Timer (control) vs Effort (assist)Gas delivery target:target: what governs gas flow Set flow vs Set insp pressureCycle: what terminates the breathCycle: VolumeVolume,, TimeTime,, FlowFlow,, PressureMacIntyre, principles of mechanical ventilation, 2008
A ventilator breath that is patient triggered,triggered,pressure targeted,targeted, and time cycled is termed:A)B)C)D)Volume AssistPressure SupportPressure ControlPressure AssistMacIntyre, principles of mechanical ventilation, 2008
A ventilator breath that is patient triggered,pressure targeted, and time cycled is termed:A)B)C)D)Volume AssistPressure SupportPressure ControlPressure Assist
A ventilator breath that is patient triggered,pressure targeted, and time cycled is termed:A)B)C)D)Volume Assist (flow targeted, volume cycled)Pressure Support (flow Cycled)Pressure Control (machine triggered)Pressure Assist (Pressure “Assist” Control)
Breath characteristics SummaryTriggerTarget / LimitCycleVolume Control (VC)TimeFlowVolumeVolume Assist (VA)EffortFlowVolumePressure Control (PC)TimePressureTimePressure Assist (PA)EffortPressureTimePressure Support (PS)EffortPressureFlowPressure Release (PR)TimePressureTimeSpontaneous (SP)EffortPressureEffort
Trigger Level of effort needed to start aventilator breath Pressure trigger - effort producespressure drop in vent circuit Flow trigger - effort draws gas out of acontinuous flow through the vent circuitMacIntyre, principles of mechanical ventilation, 2008
Trigger - PressureFlowa) Effort- Short Delayb) Pressure dropsensed as effortP AW- Short Delayc) Flow initiation byventilatord) Target reachedPesMacIntyre, principles of mechanical ventilation, 2008
Pressure Trigger:Sensitivity determined by a setpressure drop Too sensitive. Interference by motion, externalstimulation, suctioning, air leaksin circuit or chest tubes, etc. Too high. Increased work of breathing Dyssynchrony, discomfort
Flow Trigger: When the difference between inspand exp flow equals the preset flowtrigger New Inspiration Less delay in Response TimeDecreased work of breathing Maquet Pocket Guide, Modes of Ventilation , Servo-I
Flow TriggeredMaquet Pocket Guide, Modes of Ventilation , Servo-I
Gas DeliveryPressure is “dependantvariable” – varies basedon lung mechanicsVolumePressureMacIntyre, principles of mechanical ventilation, 2008
Gas DeliveryFlow and Volume aredependant variablesVolumePressureMacIntyre, principles of mechanical ventilation, 2008
Cycle what terminates the breathCycling occurs in response to: Delivered Volume Elapsed Time Predetermined decrement in Flow RateAfter cycling occurs, exhalation valves open, inspirationends, and passive exhalation occursMacIntyre, principles of mechanical ventilation, 2008
Inspiratory rise time: Time taken to reachinspiratory flow orpressure at the start ofeach breath % of cycle time incontrolled modesTime (seconds(seconds)) inPS/CPAP, or VS Maquet Pocket Guide, Modes of Ventilation , Servo-I
Inspiratory cycle off: Point at whichinspirationchanges toexpiration(Spontaneous andSupported modes)Maquet Pocket Guide, Modes of Ventilation , Servo-I
Time Constant Valve ControllerMaquet Pocket Guide, Modes of Ventilation , Servo-I
PEEP: Positive End Expiratory Pressure0 – 50 cmH2O (usually 12)Pressure to prevent collapse of the alveoli, smallairways, and maintain FRCMaquet Pocket Guide, Modes of Ventilation , Servo-I
ALI / ARDS
Respiratory System MechanicsPAlveoliPcircuit (AW)PpleuraPtracheaInspMusclesNo Flow: PAW PAlveoliMacIntyre, principles of mechanical ventilation, 2008
Under “No Flow” conditions (static) Only distending pressure in Alveoli measuredEnd--Inspiratory Pressure PA PplateauEndEnd--Expiratory Pressure PA PEEPiEndDuring “Flow Conditions”, airway pressures are affectedby both distending pressures as well as flowflow--relatedpressures
Insp flow 1 L/secExp flow (peak) 2 L/secVT 1 LiterPpeak 40 cm H2OPplateau 30 cm H2OBase P (PEEP) 0 cm H2OPeak Pes 10 cm H2OBase Pes 0 cm H2OFLowVolumePressure0PesMacIntyre, principles of mechanical ventilation, 2008
Flow Pressures:Pressures:Ppeak - Pplateau Pressure for Flow40 - 30 10 cm H2OFLowDistending Pressures:Pressures:VolumePplateau - Pbase(PEEP) Pressureto distend resp system (lung cw)30 - 0 30Peak Pes – Base Pes Pressure todistend chest wall (PCW)10 - 0 10Pressure0PesP Resp system - P Chest wall Pressure to distend lungs 20MacIntyre, principles of mechanical ventilation, 2008
Compliance The inverse of lung elastance The pressure required toexpand the lung and changethe lung volumeC V/P Cstatic - no air movementCdynamic - during active inspiration
ComplianceFLowCrs VT / (Pplateau - PEEP) 1/(301/(30-0) .0333 L/cm H2OVolumeCcw VT / Peak Pes - Base PesPressure 1/(101/(10-0) .100 L/cm H2O0CL VT / Crs - CcwPesCL VT/(Pplateau - PEEP - Peak Pes-Base Pes) 1/(301/(30-0-1010--0) .05 L/cm H2O 50 ml/cm H2OMacIntyre, principles of mechanical ventilation, 2008
PMAXPEEP
Resistance and ComplianceTransairway Pressure (PTA)The pressure required toovercome RAW as gasflows through theairways.PTA flow rate x RAWAlveolar Pressure (PA):Pressure required todeliver a tidal volumeagainst the recoil force ofthe alveoliThe effect of increased airwaysresistance on the pressure waveformPA Pplateau PstaticPIP PTA Pplateau
Resistance and ComplianceAs lung compliancedecreases the static orplateau pressureincreases resulting inincreased peakpressureExample:VT 750 mLFlow 5 cm H2OCRS 50 mL/cm H2OPplateau 15 cm H2OPTA flow x RAWPIP PTA Pplateau
Marino, The ICUBook, 2007
Flow Pattern: Volume Control VentilationConstantMaquet Pocket Guide, Modes of Ventilation , Servo-I
Flow Pattern: Pressure Control VentilationConstantDeceleratingExamples: PC, PRVC, PS, VS, SIMV (PRVC, PC) PS
Effect of changingRespiratoryFrequency (f) onCycle Time (TC)(A) RR increased to 20, cycletime decreases to 3 secand expiratory timedecreases to 1.5 sec(B)RR decreased to 12, cycletime increases to 5 sec,sec,since the inspiratory timeremains unchanged,unchanged,expiratory time increasesto 3.5 sec
Effect of changingInspiratory FlowRate on Inspiratoryand Expiratorytimes(A) Increased Inspiratory Flow Decreases insp time Longer expiration time(B) Decreased Inspiratory Flow increases insp time decreases exp time
Modes of VentilationSelection of ventilatormode depends on: Clinical setting andpatient pathophysiology Institutional guidelinesand clinician preferences
Airway PressureFlowVolumeMaquet Pocket Guide, Modes of Ventilation , Servo-I
Volume ControlVariable PressureConstant FlowPreset Tidal Volume
Controlled Mechanical VentilationVolume TargetedPressure TargetedMinute ventilation iscompletelydependent upon therespiratory rate andtidal volume set
Volume Control: Assist Control
Volume Control:Flow Adapted
Volume Control: Assist Control Advantages:Advantages: Reduced work of breathing Guarantees delivery of set tidal volume and minuteventilation Disadvantages:Disadvantages: Potential adverse hemodynamic effects May lead to inappropriate hyperventilation andexcessive inspiratory pressures Cannot ventilate effectively and consistently unlessthe airway is well sealed
Volume or Pressure Volume Assist:Assist: TV guaranteed, less worry about CO2clearance Pressure Assist:Assist: Decelerating flow more comfortable Better synchrony and more physiological
SIMV:Synchronized Intermittent MandatoryVentilation (Volume Control)
SIMV:Synchronized Intermittent MandatoryVentilation (Pressure Control)
SIMV:Synchronized Intermittent MandatoryVentilation (PRVC)
SIMV:Breath Cycle TimeMaquet Pocket Guide, Modes of Ventilation , Servo-I
Inspiratory work per unit volume done during SIMV
SIMV Advantages:Advantages: Improved synchrony Preservation of respiratory muscle function Lower mean airway pressures Decreased tendency to develop autoauto-PEEP Disadvantages:Disadvantages: Increased work of breathing compared to ACV Not shown to be effective for weaning
Pressure Support Spontaneous breathing with a ventilator “boost“boost””Patient triggers all the breathsFlow--cycled:Flow once triggered, the set pressureis sustained until the inspiratory flow tapersVT and RR (minute volume) are a consequence of thepatient--related variables (ie. the underlying disease,patientsedation) plus ventilator settingsRespir Care Clin N Am. 2005 Jun;11(2):247-63
Pressure Support
Pressure Support Gas flows into lungs ata constant pressure Since pressure isconstant, the flow willdecrease untilInspiratory cycle off (1)(1) Pressure will either risequickly or slowly,depending on Insp risetime (2)Maquet Pocket Guide, Modes of Ventilation , Servo-I
Pressure SupportAdvantages::Advantages Comfortable: patient has greater control over ventilatorcycling and flow ratesWork of breathing is inversely proportional to the level ofpressure supportDisadvantages:Disadvantages: Close monitoring is required Neither tidal volume nor minute ventilation is guaranteedRespir Care Clin N Am. 2005 Jun;11(2):247-63
7:30 AMTrauma Department32 MaleMVC – LOC & TBIGCS: 7BP: 160/80 P: 70 R: 5(L) Pupil 5 mm(R) Pupil 3 mmBilateral Breath SoundsOther trauma exam (( -)
Ventilator SettingsMode:Tidal Volume (VT):Resp Frequency (f):Insp Flow Rate (V):Control750 mL15 b/min30 L/minAirway Resistance (RAW):10 cm H2O/L/secRespiratory System Compliance (CRS):0.05 L/cm H2O50 mL/cm H2ONeurosurgery resident:“ No sedation for Neuro Exam ”
20 min later.ALARM !BP: 80/40P: 120R: 40
Auto PEEP: High respiratory rate, short expiratory timeNot enough time to exhale Air TrappingInterpretation of waveforms, Waugh, Deshpande, 2007
Interpretation of waveforms, Waugh, Deshpande, 2007
Determinants of AutoPEEP Minute Ventilation (VT and RR)Expiratory Time constantLonger I:E ratio short expiratory timeHigh resistance, floppy lungClues to diagnosis. Increase PPeak and PPlateau (VC) Decreases in VT (PC) Problems with inspiratory trigger Dyssynchrony Hemodynamic abnormalities .
Treatment of AutoPEEP Decrease Minute Ventilation (RR, VT)Increase Inspiratory Flow / pattern Increase Expiratory TimeTreat underlying cause(Bronchodilators, suction)Apply extrinsic PEEPSedationDisconnect ventilator circuit
56 year old man with SAH, receiving MV using Volume AssistControl for last 36 h. Settings are:VT: 600 R: 24 FiO2: 0.4 PEEP: 5.5. You decide to switch him toPressure Support with 22cm Insp Pressure to obtain comparable VT.He becomes dyspneic and appears to be triggering the ventilatoronly 88-10 times/min. Next maneuver should be ?ACCP Board Review 2009
A.B.C.D.E.Provide sedation and continue current settingsSwitch from Pressure to Flow triggeringAdd 5 cmH2O additional PEEP and increase until better triggerSwitch to SIMV with back up rate of 8 along with PSReturn to volume assist Control with backup rate 6/min.ACCP Board Review 2009
A.B.C.D.E.Provide sedation and continue current settingsSwitch from Pressure to Flow triggeringAdd 5 cmH2O additional PEEP and increase until better triggerSwitch to SIMV with back up rate of 8 along with PSReturn to volume assist Control with backup rate 6/min.PEEPi-inducedtriggering loadACCP Board Review 2009
Modern Ventilators: Computer Based & SmartUse complex algorithms Airway Pressures (ARDs Net)Mode SwitchWaveform analysisSynchronyPatient ComfortWeaningOpen Lung Tool
Open Lung Tool (OLT)Pressure Control Ventilation *
NAVAAmirali Nader, M.D.Critical Care MedicineSuburban HospitalJohns Hopkins Medicine
Trigger DelayTobin. N Engl J Med 2001; 344:1986-1996 Data from Jubran et al and Parthasarathy et al
Cycle-off DelayTobin. N Engl J Med 2001; 344:1986-1996 Data from Jubran et al and Parthasarathy et al
AsynchronyTobin. N Engl J Med 2001; 344:1986-1996 Data from Jubran et al and Parthasarathy et al
Synchrony: Initiation, delivery andInitiation,termination of thepatient‟s and theventilator‟s breathscoincide with each otherSynchronyDyssynchrony
Dyssynchrony: 20-30% of patients on ventilators exhibit20dyssynchronyPatients with frequent ineffective triggering mayreceive excessive levels of ventilatory support
NormalMuscleWastedEffortsEccentric contractions
Rapid Disuse Atrophy of Diaphragm Fibersduring asynchronous ventilation:
Usual solution to PatientPatient-VentilatorAsynchrony: Adjust Ventilator SettingsIncrease SedationNeuromuscular blockersVIDD – Ventilator InducedDiaphragmatic DysfunctionDisuse Atrophy2:00 AM PAGE !Prolonged ICU stay
Neurally Adjusted VentilatoryAssist: (NAVA) New Spontaneous,Interactive mode ofmechanical ventilation Delivers ventilatory assist inProportion to and inSynchrony with thepatient‟s Edi signal
Edi Signal: Edi - Electrical Activity of diaphragm(measured 62.5 times per second) Edi Peak –The amount of impulseimpulse sent togenerate tidal volume breath by breath. Edi Min – The tonic contractility of thediaphragm at rest.rest. Physiologic reflection of dederecruitment.
Ideal TechnologyCentral nervous systemPhrenic nerveVentilatorDiaphragm excitationDiaphragm contractionChest wall, lung and esophageal responseflow, pressure changesCurrent Technology
Ideal TechnologyCentral nervous systemPhrenic nerveDiaphragm excitationNAVAVentilatorDiaphragm contractionChest wall, lung and esophageal responseflow, pressure changesCurrent Technology
Servo-i ventilator
Edi Catheter SizesSize 6 Fr / 49 cmNeonateSize 6 Fr / 50 cmNeonateSize 8 Fr / 100 cmPediatricSize 12 Fr / 125 cmPediatricSize 8 Fr / 125 cmAdultSize 16 Fr / 125 cmAdult
Instructions for catheter:1. Dip the Edi Catheter in water for a few seconds to activate itslubrication prior to insertion, avoiding wetting connectors.2. Insert Catheter and advance it down the esophagus3. Confirm placement
Edi Catheter Anatomy:
Insertion Depth:Coefficient for nasal insertion 0.9Coefficient for oral insertion 0.8Insertion distance Y for oral insertionFr/cmCalculation of Y16 FrNEX cm · 0.8 18 Y cm12 FrNEX cm · 0.8 15 Y cm8 Fr 125 cmNEX cm · 0.8 18 Y cm8 Fr 100 cmNEX cm · 0.8 8 Y cm6 Fr 50 cmNEX cm · 0.8 3.5 Y cm6 Fr 49 cmNEX cm · 0.8 2.5 Y cmD. Rowley, Univ of Virginia, Resp Therapy Dept.
Catheter Insertion:
Edi Catheter Insertion:Check position of EdiCatheter like afeeding tubeaccording to hospitalguidelines(i.e. portable CXR)D. Rowley, Univ of Virginia, Resp Therapy Dept.
Catheter Insertion:IIIIIIIVEdiD. Rowley, Univ of Virginia, Resp Therapy Dept.
Good position:P-wave / QRSProgressionD. Rowley, Univ of Virginia, Resp Therapy Dept.
Too Deep (pull catheter back)
Too Shallow. (advance catheter)
Factors affecting Edi signal: Muscle relaxants / paralyticsCNS depressant drugs, sedationHyperventilationHigh PEEP , High supportpressure
Volume Control with Edi:PressureFlowVolumeEdi Catheter
NAVA PrePre-view: unmasking asynchrony
Same patient on NAVA:Breath to Breath SynchronyDecreased Airway Pressure
Asynchrony during VC:D. Rowley, Univ of Virginia, Resp Therapy Dept.
Same Patient on NAVA:D. Rowley, Univ of Virginia, Resp Therapy Dept.
0.1-2.0 microvoltsApneaBackup
Starting NAVA: Preview ScreenD. Rowley, Univ of Virginia, Resp Therapy Dept.
Increase NAVA level until Pest peak current PAPPestEstimated Ppeak (Pest) in NAVA NAVA Level x (Edi peak – Edi min) PEEP
Activate NAVA modeMonitor:- VT- Edi peak- PAP- VS andWOBIncreasing NAVA will result in:Decrease in Edi Peak, stableVt, and stabilization of PAPD. Rowley, Univ of Virginia, Resp Therapy Dept.
NAVA Inspiration: Triggering of a breath iseither EdiEdi,, flow orpressure trigger Even if the breath istriggered on flow orpressure, the breathdelivered to the patientremains proportional tothe patient’s Edi signal 1st come 1st serve basis1: Edi Triggered Breath2: Flow Triggered Breath
NAVA Inspiratory Trigger: NAVA is triggered by an increase in Edi from the Ediminimum and not at any absolute level of EdiSet high enough toavoid noiseinterferenceHere, vent willprovide supportwhen Edi above 0.7Neth J Crit Care 2007:11(5):243-252
NAVA Expiration: If the pressure increases 3cmH2O above the inspiratorytarget pressure When the Edi signal decreasesbelow 70% of the peak valueduring the ongoing inspiration Also, If the upper pressure/timelimit is exceeded(time for adults 2.5 sec)
The NAVA signal – what it means NAVA level is the factor bywhich the Edi signal ismultiplied to adjust theamount of assist deliveredto the patient NAVA level varies fordifferent patients becausethey will require differentassist levels. Typically 1.0 - 4.0 cmH20/μVAm J Respir Crit Care Med 2001Nat Med 1999; 5(12): 1433-1436
The pressure delivered by the ventilator is derived from thefollowing formula:NAVA level x (Edi signal – Edi min) PEEPAm J Respir Crit Care Med 2001Nat Med 1999; 5(12): 1433-1436
NAVA: Physiologic Principles Neural signal is increased as respiratorymuscles weaken relative to loadSynchrony in assist delivery is inherentUnloading can be done objectivelyProportional assist gives freedom forvariable breathingPatient „Oscillator‟ controls breath timingand tidal volume
What we know so far NAVA Improves patient ventilatorsynchrony(potentially less sedation) Allows real time monitoring ofrespiratory drive Adapts to patient‟s alteredrespiratory drive and reflexes Less damage to muscles, lessdisuse atrophyNeth J Crit Care 2007:11(5):243-252Chest 2007; 131(3): 711-717
Applications Good tool for weaning. Can watch Edi signaldecrease as respiratoryfunction improvesProportional assist givesfreedom for variable breathingThe patient will control TidalVolume & Respiratory Rate
Applications: Spinal Cord InjuryCardiothoracic surgeryEdi signal as a tool todetect overover-sedationand neuromuscularrecover (ie. GuillanBare)
Limitations: Lack of large randomizedclinical trialsUncertainty whethersynchrony leads to betteroutcomeReliability of equipment –NAVA Catheter integrityafter prolonged ventilationCost of equipment andresources
Mechanical Ventilation: Schedule History, Concepts and Basic Physiology – Nader Volume Control Ventilation (CMV, ACV) – Nader Intermittent Mandatory Ventilation (SIMV) – Nader Pressure Support Ventilation (PSV) – Nader Pressure Control Ventilation (PCV) –
Mechanical Ventilation: Schedule History, Concepts and Basic Physiology - Nader Volume Control Ventilation (CMV, ACV) - Nader Intermittent Mandatory Ventilation (SIMV) - Nader Pressure Support Ventilation (PSV) - Nader Pressure Control Ventilation (PCV) - Junker Pressure Regulated Volume Control (PRVC) - Junker
(10) A mode of ventilation is classified according to its control variable, breath sequence, and targeting schemes. CMV continuous mandatory ventilation IMV intermittent mandatory ventilation CSV continuous spontaneous ventilation VC volume control PC pressure control TAXONOMY FOR MECHANICAL
ventilation à haute fréquence aboutirent à la mise au point de deux types très différents d'appareils : ceux délivrant la ventilation par percussions à haute fréquence ou high frequency percussive ventilation (HFPV) et ceux délivrant la ventilation à percussions intrapulmonaires ou intra-pulmonary percussive ventilation (IPV).
Mechanical Ventilation is indicated in pandemic flu for acute respiratory failure, defined as insufficient oxygenation, insufficient alveolar ventilation, or both. The principal benefits of mechanical ventilation are improved gas exchange and decreased work of breathing. Mechanical ventilation can be volume, pressure, flow or time-limited.
With “Basic Assessment and Support in Intensive Care” by Gomersall et all as a foundation, I built using the humongous ndand canonical “Principles and Practice of Mechanical Ventilation” by Tobins et al – the 1442 page 2 edition CMV: Continuous Mandatory Ventilation VOLUME CONTROLLED CMVFile Size: 309KBPage Count: 9Explore furtherContinuous Mandatory Ventilation - an overview .www.sciencedirect.comSynchronized Intermittent Mandatory Ventilationpubmed.ncbi.nlm.nih.govContinuous mandatory ventilation - Wikipediaen.wikipedia.orgRecommended to you b
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