Summary: Extracorporeal CO₂ Removal (ECCO₂R)

1. Background & Rationale

  • Hypercapnia has harmful effects: neurological, pulmonary hypertension, right heart failure, immunosuppression, and worsened inflammation.

  • 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):

  • Allows lung-protective or ultra-protective ventilation (lower tidal volumes, plateau pressures).

  • Reduces risk of ventilator-induced lung injury.

b. COPD Exacerbations:

  • Reduces respiratory rate and work of breathing.

  • Allows longer expiratory time → prevents dynamic hyperinflation.

  • Corrects acidosis and may reduce need for invasive ventilation.

3. Evidence & Trials

  • Meta-analyses & small RCTs: show improved CO₂ clearance and reduced dyspnea but mixed outcomes for mortality and length of stay.

  • VENT-AVOID trial: ECCO₂R did not significantly improve ventilator-free days; higher mortality noted in NIV + ECCO₂R group.

  • NOVA study: demonstrated feasibility of ultra-protective ventilation facilitated by ECCO₂R but with notable device-related complications.

  • 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

  • Arteriovenous (AV) systems:

    • No pump; rely on patient’s arterial–venous pressure gradient.

    • Require stable hemodynamics and carry risk of distal ischemia.

  • Venovenous (VV) systems:

    • Pump-driven; more flexible and suitable for unstable patients.

    • Safer (avoid arterial cannulation) and more commonly used.

  • Flow rates & efficiency:

    • Low-flow devices (250–1000 ml/min) remove 40–150 ml/min of CO₂.

    • Efficiency depends on blood flow, sweep gas flow, and membrane surface area.

    • Hemolung: portable, low-to-moderate flow (~500–700 ml/min).

    • ProLUNG, iLA, and dialysis-adapted systems: higher flows, larger membranes.

      Commercial systems:

5. Complications

  • Bleeding, thrombosis, hemolysis, brain hemorrhage, pneumothorax.

  • Circuit thrombosis risk higher at low flow rates → need higher anticoagulation targets (aPTT/ACT).

6. Management & Weaning

  • Careful anticoagulation is essential.

  • Weaning considered once:

    • pH > 7.3,

    • respiratory rate < 25/min,

    • tidal volume ~6 ml/kg PBW,

    • stable gas exchange (PaO₂/FiO₂ > 200).

  • Gradual reduction of sweep gas before device removal.

7. Conclusion

  • ECCO₂R may be helpful in:

    • Severe COPD exacerbations (reducing need for intubation).

    • Facilitating ultra-protective ventilation in ARDS.

  • Limitations:

    • Evidence does not yet show consistent survival benefit.

    • High complication rates (bleeding, thrombosis).

  • Future role: still debated, requires further large RCTs.

 

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