One-Lung Ventilation (OLV) for thoracic surgery or unilateral chest trauma requires isolating the non-ventilated operative lung while providing protective ventilation to the dependent lung.
Key Physiological Equations & Formulas
- Hypoxic Pulmonary Vasoconstriction (HPV): $$\text{Diverts } 40-50\% \text{ of non-ventilated lung blood flow to the ventilated lung}$$ Improves V/Q matching during OLV; blunted by volatile anesthetics, vasodilators, and hypercapnia.
Practical Clinical Pearls & Bedside Rules
- Lung Isolation Devices: Double-Lumen Tubes (Left DLT preferred in most cases) or bronchial blockers. Verify position with pediatric fiberoptic bronchoscope.
- Protective OLV Strategy: Ventilate the single dependent lung with low tidal volumes (4-5 mL/kg PBW), moderate PEEP (5-8 cmH2O), and driving pressure < 15 cmH2O.
Initial Settings & Clinical Titration Protocol
| Parameter | Recommended Initial Setting | Titration Goal / Safety Threshold |
|---|---|---|
| Tidal Volume in OLV | 4 - 5 mL/kg PBW (single lung) | Prevents volutrauma in single ventilated lung. |
| CPAP to Non-Ventilated Lung | 1 - 5 cmH2O CPAP with 100% O2 to operative lung | Dramatic rescue for refractory hypoxemia during OLV. |
Bedside Troubleshooting & Red Flags
Warning
DLT Malposition: Sudden high peak pressures and desaturation during OLV are most often due to tube displacement. Re-examine with bronchoscope.
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.