Veno-Venous Extracorporeal Membrane Oxygenation (VV-ECMO) takes over systemic oxygenation and CO2 removal, allowing the mechanical ventilator to deliver ultra-protective 'rest' ventilation.
Key Physiological Equations & Formulas
- Rest Lung Mechanical Targets: $$V_T = 2-4\text{ mL/kg PBW}, \quad P_{plat} \le 20-25\text{ cmH}_2\text{O}, \quad \Delta P \le 10\text{ cmH}_2\text{O}, \quad RR = 4-10\text{ bpm}$$ Virtually abolishes mechanical power and ventilator-induced lung injury.
Practical Clinical Pearls & Bedside Rules
- ECMO Membrane Sweep Gas: Titrate sweep gas flow (L/min) to control arterial PaCO2 and pH. Titrate ECMO pump blood flow ($Q_{b} \approx 3-5\text{ L/min}$) to maintain $SaO_2 > 85-90\%$.
- Maintaining PEEP during ECMO: Do NOT discontinue PEEP; maintain moderate PEEP (10-15 cmH2O) to prevent complete dependent alveolar consolidation during rest ventilation.
Initial Settings & Clinical Titration Protocol
| Parameter | Recommended Initial Setting | Titration Goal / Safety Threshold |
|---|---|---|
| Ventilator Mode | Pressure Control (PC-CMV) with long Ti (1.5-2.0 s) | Gentle, non-injurious pressure delivery. |
| FiO2 on Ventilator | 0.30 - 0.40 | Rest lungs from toxic hyperoxia while ECMO oxygenates blood. |
Bedside Troubleshooting & Red Flags
Warning
Acute Recirculation in VV-ECMO: Occurs when oxygenated blood from return cannula is drawn directly into drainage cannula. Check cannula spacing on CXR/echocardiogram.
Key Takeaways & Summary
- Always evaluate patient synchrony and physiological response before changing ventilator parameters.
- Maintain lung-protective strategies to minimize driving pressure ($\Delta P$) and mechanical power.
- Continuously reassess liberation and extubation readiness on daily morning rounds.