Summary: Extracorporeal CO₂ Removal (ECCO₂R)
1. Background & Rationale
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Hypercapnia has harmful effects: neurological, pulmonary hypertension, right heart failure, immunosuppression, and worsened inflammation.
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CO₂ is mainly transported dissolved/bicarbonate → easier to remove with low-flow extracorporeal circuits compared to oxygen.
2. Clinical Indications
a. ARDS (Acute Respiratory Distress Syndrome):
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Allows lung-protective or ultra-protective ventilation (lower tidal volumes, plateau pressures).
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Reduces risk of ventilator-induced lung injury.
b. COPD Exacerbations:
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Reduces respiratory rate and work of breathing.
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Allows longer expiratory time → prevents dynamic hyperinflation.
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Corrects acidosis and may reduce need for invasive ventilation.
3. Evidence & Trials
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Meta-analyses & small RCTs: show improved CO₂ clearance and reduced dyspnea but mixed outcomes for mortality and length of stay.
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VENT-AVOID trial: ECCO₂R did not significantly improve ventilator-free days; higher mortality noted in NIV + ECCO₂R group.
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NOVA study: demonstrated feasibility of ultra-protective ventilation facilitated by ECCO₂R but with notable device-related complications.
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REST trial: no mortality benefit at 90 days; higher adverse events (bleeding, hemolysis).
➡️ Conclusion: ECCO₂R is feasible but benefits remain uncertain; risk of complications significant.
4. Devices & Techniques
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Arteriovenous (AV) systems:
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No pump; rely on patient’s arterial–venous pressure gradient.
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Require stable hemodynamics and carry risk of distal ischemia.
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Venovenous (VV) systems:
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Pump-driven; more flexible and suitable for unstable patients.
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Safer (avoid arterial cannulation) and more commonly used.
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Flow rates & efficiency:
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Low-flow devices (250–1000 ml/min) remove 40–150 ml/min of CO₂.
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Efficiency depends on blood flow, sweep gas flow, and membrane surface area.
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Hemolung: portable, low-to-moderate flow (~500–700 ml/min).
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ProLUNG, iLA, and dialysis-adapted systems: higher flows, larger membranes.
Commercial systems:
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5. Complications
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Bleeding, thrombosis, hemolysis, brain hemorrhage, pneumothorax.
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Circuit thrombosis risk higher at low flow rates → need higher anticoagulation targets (aPTT/ACT).
6. Management & Weaning
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Careful anticoagulation is essential.
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Weaning considered once:
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pH > 7.3,
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respiratory rate < 25/min,
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tidal volume ~6 ml/kg PBW,
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stable gas exchange (PaO₂/FiO₂ > 200).
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Gradual reduction of sweep gas before device removal.
7. Conclusion
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ECCO₂R may be helpful in:
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Severe COPD exacerbations (reducing need for intubation).
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Facilitating ultra-protective ventilation in ARDS.
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Limitations:
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Evidence does not yet show consistent survival benefit.
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High complication rates (bleeding, thrombosis).
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Future role: still debated, requires further large RCTs.