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A&E(VINAYAKA) MECHANICAL VENTILATION IN ARDS / ALI Dr. V.P.Chandrasekaran,
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MECHANICAL VENTILATIONIN
ARDS / ALI
Dr. V.P.Chandrasekaran,
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ARDS
Clinical syndrome ofSevere dyspnea of rapid onsetHypoxemia Diffuse pulmonary infiltrates
leading to respiratory failure.
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ALI
A less severe disorder but has the potential to evolve into ARDS
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DIAGNOSING CRITERIA
Acute onsetChest X Ray - Acute Bilateral alveolar or interstitial infiltrates PaO2/FIO2 < 300 mmHg - ALI
PaO2/FIO2 < 200 mmHg - ARDS
PCWP < 18 mmHg or CVP < 12 mmH2O
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ARDS:Pathogenesis
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CLINICAL COURSE
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NEEDS AGGRESSIVE MANAGEMENT
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VENTILATOR STRATEGIES
Non Invasive VentilationInvasive ventilation
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Goals of ventilation
To improve O2 & CO2 gas exchange
Alveolar recruitment
To assist respiratory muscles
To improve the lung compliance
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SCENARIO - 1
Mr . X , 30 year maleFever x 5 daysCough with expectoration x 5 daysBreathlessness Grade IV x 2 hours
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Chest X Ray
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ABG @ FiO2 0.4Measured Data
Ph -7.513pCO2 -25.4pO2-66.5Na+ -136K+ -3.54Cl- -101
Calculated DataHCO3 (act)-19.9HCO3 (std)-23.4BE (ect) -3.1BE (B) -1.3ctCO2 -20.7AnionGap -18.8O2 Sat -98%
ACUTE RESPIRATORY ALKALOSIS
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PaO2 / FiO2
= 66.5 / 0.4
=166.25
CVP 8 cm Hep Saline
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ARDS:Treatment
Recent decrease of mortality Treatment of underlying causeBetter supportive ICU Care
Prevention of infectionsAppropriate nutritionGI prophylaxisThromboembolism prophylaxis
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BiPAP
Pressure Support
– 15
PEEP – 8
FiO2 – 0.4
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Contraindications to BiPAP
Apnoea
Active ischemic cardiac disease
Unable to handle secretion
Homodynamic instability
Facial trauma
No respiratory drive
Claustrophobia
Poor cooperation
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ADMISSION DISCHARGE
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SCENARIO - 240 year maleCellulitis of Left legBreathlessness grade IV since morning
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Chest X Ray
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Not co operative for Bi-PaP
PaO2 / FiO2
= 60.0 / 0.4
=150
CVP 7 cm Hep Saline
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Requires Mechanical ventilation
Goals?To improve oxygenation
Alveolar recruitment
To assist respiratory muscles
To improve the lung compliance
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To improve Oxygenation
More inspiratory timeOptimum PEEPHigher FiO2 - initially
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Alveolar recruitment
Optimum PEEPMore inspiratory timeLow rate
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Protective ventilation
Smaller tidal volumes Avoid overdistentionTolerate “permissive hypercarbia”
“Open lung” ventilation with PEEP
Avoid alveolar collapse and reopening
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Collapse/ atelectosis/ ARDS
Increases Surface area for gas exchangeOpens the collapsed lung
Collapsed alveoli
After PEEP
PEEP
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To assist respiratory muscles
Ventilator supportIf needed to rest respiratory muscles with paralysis
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To improve the lung compliance
To keep the PEEP above the lower inflection pointParalysisPressure control mode
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Optimal “PEEP”
Positive end-expiratory pressure should be high enough to shift the end-expiratory pressure above the lower inflection point by 2-3 cm H2O (usually 12-15 cm H2O)Allows maximal alveolar
recruitmentDecreases injury by repeated
opening and closing of small airways
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Settings
Pressure control – to reach Vt 400ml
( 65 x 6 = 390 ml )
Rate : 10-12/minI:E : 1:1PEEP: 10-15CMH2O
FiO2 : 100% -40%
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Will it result in Respiratory acidosis?Yes. But still needed…!
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ARDS:Permissive Hypercapnoea
Permissive hypercapniapH >7.2PCo2 <80mmHg
ContraindicationHypotensionBrain injuryBarotrauma
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Watch for
Barotrauma / pneumothoraxHypercapnoeaRespiratory acidosis
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What to do if PCo2 raises above 80 mmHg
or pH <7.2Increase VtDecrease PEEPIncrease rateDecrease inspiratory time
And reassess
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If signs of pneumothorax appearsICDIf tension pneumothorax – needle decompression - ICD
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What to do if saturation does not improve?
Increase PEEPIncrease Inspiratory time (Inverse)Increase FiO2Increase Vt
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Why should I aim for low FiO2 <60
High FiO2 can result in oxygen toxicity and free radical injury and further precipitate ARDS and MOF
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Treat the cause
Avoid frequent suctioning
Frequent ABG assesment
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Adjuncts
Paralyze & SedateCVP guided fluidsVasopressersDVT prophylaxisStress ulcer/Bed sore prophylaxisNutrition
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ARDS Treatment
Prone positioningSteroidsAnti oxidantNitric oxideSurfactantAnti-inflammatory StrategiesProstaglandin agonist/inhibitorsLisofylline and pentoxifyllineAnti IL-8
?
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THANK YOU
