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Mechanical Ventilation 1
Shari McKeown, RRTRespiratory Services - VGH
Objectives
Describe indications for mcventDescribe types of breaths and modes of ventilationDescribe compliance and resistance and how this affects ventilationDescribe ventilator troubleshooting
Indications for McVent
Oxygenation abnormalitiesRefractory hypoxemiaNeed for positive end expiratory pressure (PEEP)Excessive work of breathing
Indications for McVent –cont’d
Ventilation abnormalitiesRespiratory muscle dysfunction
• Respiratory muscle fatigue• Chest wall abnormalities• Neuromuscular disease
Decreased ventilatory driveIncreased airway resistance and/or obstruction
Modes of Ventilation
ASV, APRV, AV, AutoMode, Bilevel, BiPAP, EPAP, Fluid Logic, HFJV, HFOV, IPPV, IPAP, MMV, NEEP, PAV, PCV+, PCIRV, PCSIMV, PRVS, PRVC, PV, VCIRV, IRV, VS, etc, etc, etc!!!
Types of Ventilator Modes
Mandatory Operator sets RROperator sets start, stop, and everything in betweenPatient can trigger extra mandatory breaths
SpontaneousPatient sets RRPatient controls start, stopPatient triggers all breaths
Types of Ventilator BreathsMandatory
Volume Breath• Flow set• Volume cycled
Pressure Breath• Pressure set• Time cycled
SpontaneousPressure supported breath
• Pressure set• Patient insp flow cycled
Choosing a Mode
Consider trial of NPPVDetermine patient needsIdentify goals
Adequate ventilation and oxygenationDecreased work of breathingPatient comfort and synchronyRemove vent asap
Spontaneous Ventilation
Continuous Positive Airway Pressure (CPAP)
No machine breaths deliveredAllows spontaneous breathing at elevated baseline pressurePatient has complete control over RR and tidal volume
Pressure SupportRR triggered by patientPreset level of inspiratory support delivered Cycles to expiration when inspiratory flow slows to preset levelVT depends on compliance, resistance, pressure level, and patient effort
Pressure Support – cont’dAdvantages
Patient comfortDecreased work of breathingMay enhance patient-ventilator synchrony
DisadvantagesVariable volumesInappropriate supportRelies on apnea backupLeaks may interfere with cycling
Assist-Control (Volume)Set RR, set tidal volume, insp pressure variablePatient triggers extra breaths with full tidal volumeAdvantages: guarantees minute ventilationDisadvantages: hyperventilation, hemodynamic effects, ‘breath stacking’
Assist-Control (Pressure)Set RR, set insp pressure, tidal volume variablePatient triggers extra breaths with full pressureAdvantages: limits pressureDisadvantages: hyperventilation, hemodynamic effects, ‘breath stacking’
Synchronized Intermittent Mandatory Ventilation (SIMV)
Mandatory breaths – volume or pressure breathsSpontaneous breaths – pressure support
SIMV – cont’d
AdvantagesLess hemodynamic effectsLess inappropriate hyperventilationGuarantees some minute ventilation
Disadvantages:Not physiological
Measurements
ComplianceResistancePeak airway pressurePlateau pressure
Compliance
Measures compliance of the lung and thoraxTidal volume / Plateau-PEEPUnits = ml/cmH20
Resistance
Measures airway resistanceLengthViscosityFlowRadius4
Peak-plateau / FlowrateUnits = cmH20/Lps
Peak and Plateau Pressures
Peak airway pressure reflectsBaseline (PEEP)Pressure due to compliance (L+T)Pressure due to resistance
Plateau pressure (breath hold) reflectsBaseline (PEEP)Pressure due to compliance (L+T)(alveolar distending pressure)
Waveform
Troubleshooting
Mechanical Ventilation 2
Fundamentals of Critical Care Support
Objectives
Initiation of mcventMonitoringImproving oxygenationImproving ventilationObstructive Lung DisordersRestrictive Lung DisordersPediatric considerations
Initiation of McVentChoose your modeSet minute ventilation for pH
RRVT (8-10 ml/kg)I:E
Set oxygenation for SpO2 or SaO2PEEPFiO2
Trigger level
Set sedation, analgesia, NM blockadeMonitors
ECG, SpO2, Vitals, ObservationAlarms
Hi/Low pressureLow volumeApnea
Humidification
Initiation cont’d
Initiation cont’d
EvaluationCXRPeak/plateauExhaled VT and RR(TOT)Patient-Ventilator synchronyAutopeepSpO2, ABGHemodynamics
Improving Oxygenation
FiO2Mean Airway Pressure
PEEP• Recruit lung• Improve compliance• Redistribute lung water/blood
Insp pressureInspiratory time
Goal Sp02 >92%, FiO2 <0.50
Improving Ventilation
Tidal VolumeWatch Plateau
Respiratory RateWatch for Autopeep
Goal pH = normal
Obstructive Lung Disorders
Asthma/COPDInflammationBronchoconstrictionInc. mucous prod/Dec. clearanceDecreased expiratory flowrates
• Autopeep• Hemodynamic compromise• Barotrauma
Obstructive Lung Disorders -Ventilator Strategies
Decrease RRSedation to decrease drive
Permissive HypercapniapH >7.25Contraindications Heads, Hearts
Plateau <30cmH20
Restrictive Lung Disorders
Intrapulmonary ARDSCHFPneumoniaFibrosis
ExtrapulmonaryObesityPregnancyAscites
Restrictive Lung Disorders –Ventilatory Strategies
IntrapulmonaryRecruit collapsed lung
• High PEEP• Increase TI
Prevent overdistension• Plateau <30cmH20• VT 4-6 ml/kg
Goal FiO2 <0.50?Extrapulmonary
Same as above, with Plateau <40cmH20
Pediatric Considerations
Infants (<5 kg)Time-cycled, pressure limited modesStart Peak pressure 18-20 cmH20TI .5-.6 secVT to chest expansion or 8 ml/kgPEEP 2-4
Pediatric Considerations –cont’d
ChildrenSIMV modeVT 8-10 ml/kgTI
• Infants - .5-.6 sec• Toddlers - .6-.8 sec• Older - .8-1.0 sec
RR < 18-20 Peep 5
Mechanical Ventilation