🔹 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:

  • PF <50 for >3 hrs

  • PF <80 for >6 hrs

  • pH <7.25 with PaCOâ‚‚ >60 for >6 hrs

  • 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:

  • <150 → Proning

  • <100 → Severe ARDS

  • <80 → Consider ECMO

    • NM Blockade: Use <48 hrs if PF <150

    • ECMO Decision: Murray Score >3, failing protective ventilation

 

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