🔹 Learning Objectives
• Classify four main types of respiratory failure
• Define updated Berlin definition of ARDS
• Identify common causes and triggers for ARDS
• Explain key pathophysiological changes in ARDS
• Outline evidence-based conventional ARDS management
• Recognize clinical criteria and timing for VV ECMO initiation
🔹 Case Summary
• 42M teacher, COVID-19+, severe hypoxemia unresponsive to NIV
• Progressed to severe ARDS by Day 2
• Intubated, lung-protective ventilation + NM blockade + proning
• Day 4: VV ECMO initiated due to refractory hypoxia
• Day 12: Successful decannulation
• Day 13: Extubated, transitioned to nasal cannula
🔹 Types of Respiratory Failure
• Type 1: Hypoxemic (PaO₂ <60, normal/low PaCO₂)
• Type 2: Hypercapnic (PaCO₂ >45, pH <7.35)
• Type 3: Post-op (due to low FRC)
• Type 4: Circulatory/metabolic (shock-related)
🔹 ARDS Definitions & Updates
• Berlin definition: Within 1 week, bilateral infiltrates, no cardiac cause, PF ratio-based severity
• Global update: Adds lung US, SpO₂/FiO₂ criteria, HFNC ≥30 L/min
• New categories: Non-intubated ARDS, ARDS in resource-limited settings
🔹 Common ARDS Etiologies
• Direct: Pneumonia, aspiration, trauma
• Indirect: Sepsis, pancreatitis, transfusion
🔹 Pathophysiology of ARDS
• Exudative Phase (0–7d): Inflammation, capillary leak, edema
• Proliferative Phase (7–21d): Alveolar healing, surfactant production
• Fibrotic Phase (>21d): Fibrosis, pulmonary hypertension, poor prognosis
🔹 Evidence-Based ARDS Management
• Lung-protective ventilation: TV 6 ml/kg, Pplat <30, Driving P <15
• Proning: ≥16 hrs/day if PF <150 (PROSEVA trial)
• Fluids: Conservative strategy improves outcomes (FACTT)
• Steroids: Mixed evidence; beneficial in COVID-19 ARDS
• NM Blockade: Consider if PF <150 with dyssynchrony (ACURASYS)
• Recruitment maneuvers & HFOV: Not recommended (OSCILLATE, OSCAR)
🔹 VV ECMO: Indications & Timing
• Indications:
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PF <50 for >3 hrs
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PF <80 for >6 hrs
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pH <7.25 with PaCOâ‚‚ >60 for >6 hrs
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Murray Score >3
• CESAR Trial: Improved outcomes when referred to ECMO center
• EOLIA Trial: Trend toward mortality reduction, confirmed ECMO safety
• COVID-19 Data: Comparable outcomes to non-COVID ARDS in high-volume centers
🔹 RESP Score
• Tool to predict ECMO outcome
• 12 variables; helps stratify patients into survival likelihood categories
• Class 1: >90% survival | Class 5: <20%
🔹 Practical Considerations for VV ECMO
• Favorable: <7d MV, no severe comorbidities, good lung compliance
• Caution: MV >14d, frailty, irreversible causes, multiorgan failure, bleeding risk
• Anticoagulation: ECMO can be run anticoag-free in selected trauma cases
🔹 Summary Recommendations
• Start lung-protective strategy early
• Use prone positioning if PF <150
• NM blockade if PF <150 and dyssynchrony
• Early ECMO if PF <80 or severe acidosis despite optimization
• Refer early to experienced ECMO center
• Avoid recruitment maneuvers & HFOV
• Tailor steroids and fluids based on patient profile
🔹 Golden Numbers in ARDS
• TV: 6–8 ml/kg
• Pplat: <30
• Driving Pressure: <15
• PF Thresholds:
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<150 → Proning
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<100 → Severe ARDS
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<80 → Consider ECMO
• NM Blockade: Use <48 hrs if PF <150
• ECMO Decision: Murray Score >3, failing protective ventilation
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