One Lung Ventilation - Placement and Ventilation Basics

Key Points

• OLV produces an intentional intrapulmonary shunt and commonly reduces oxygenation.
• Double-lumen tubes and bronchial blockers are both effective lung-isolation devices.
• Confirm isolation-device position with flexible bronchoscopy after positioning.
• Use predicted body weight for tidal-volume selection.
• Lung-protective OLV generally uses approximately 4 to 6 mL/kg predicted body weight with individualized PEEP.
• Unexpected hypoxemia should first prompt a structured check for device malposition and reversible ventilation problems.
• CPAP to the operative lung can improve oxygenation when the surgical field allows it.
• Severe hypoxemia may require temporary return to two-lung ventilation.
• Communication with the surgeon is essential during rescue maneuvers.

Algorithm

1. Place and bronchoscopically confirm the lung-isolation device.
2. Reconfirm device position after lateral positioning.
3. Begin OLV with low tidal volume based on predicted body weight and individualized PEEP.
4. Monitor SpO2, capnography, airway pressure, compliance, and hemodynamics.
5. For hypoxemia, increase FiO2 and verify circuit, ventilation, and hemodynamics.
6. Use bronchoscopy to check device position and clear obstruction.
7. Recruit the dependent lung and optimize PEEP if appropriate.
8. If still hypoxemic, consider CPAP or oxygen to the operative lung after surgical discussion.
9. For severe refractory hypoxemia, temporarily resume two-lung ventilation while correcting the cause.
10. At completion, reinflate carefully and plan postoperative respiratory support and analgesia.

Clinical Synopsis & Reasoning

OLV creates a large obligatory right-to-left shunt because the nonventilated lung continues to receive some pulmonary blood flow. Hypoxic pulmonary vasoconstriction reduces that shunt over time, but oxygenation commonly falls after lung isolation. The anesthesiologist must balance adequate gas exchange with avoidance of ventilator-induced lung injury in the dependent ventilated lung.

Lung isolation is usually achieved with a double-lumen endotracheal tube or a bronchial blocker. A double-lumen tube allows rapid isolation, suction, and selective CPAP to the operative lung but is larger and requires specific positioning. A bronchial blocker can be placed through a standard endotracheal tube and is useful in difficult airways, tracheostomy, or anticipated postoperative ventilation. Either device can migrate with lateral positioning, surgical manipulation, or changes in head and neck position.

Flexible bronchoscopy is the standard method to confirm device position after placement and again after patient positioning. Unexpected hypoxemia should trigger immediate reconsideration of device position because malposition is a common reversible cause. Also assess the ventilated lung for endobronchial obstruction, secretions, atelectasis, pneumothorax, bronchospasm, and excessive airway pressure.

Use predicted body weight rather than actual body weight for tidal-volume selection. Contemporary thoracic anesthesia practice favors lung-protective OLV with approximately 4 to 6 mL/kg predicted body weight, limitation of airway pressures, appropriate respiratory rate, and individualized PEEP. Excessive tidal volume and high driving pressure can injure the dependent lung, while excessively low volume without adequate PEEP can promote atelectasis.

Treatment Strategy & Disposition

Before initiating OLV, confirm adequate oxygenation and hemodynamics during two-lung ventilation. Position the isolation device with bronchoscopy and reconfirm after lateral positioning. Start OLV with a low tidal volume based on predicted body weight, often approximately 4 to 6 mL/kg, and select PEEP according to oxygenation, compliance, and recruitment response. Adjust respiratory rate to manage carbon dioxide while avoiding unnecessary dynamic hyperinflation.

If hypoxemia develops, increase inspired oxygen promptly while troubleshooting. Confirm adequate ventilation and rule out circuit or airway problems. Perform bronchoscopy to verify the double-lumen tube or blocker and clear secretions. Recruit the dependent lung when appropriate and optimize PEEP. Correct hypotension and low cardiac output because reduced mixed venous oxygen content worsens arterial desaturation.

If oxygenation remains inadequate and the surgical field permits, apply low-level CPAP or oxygen insufflation to the nondependent operative lung. Intermittent reinflation or temporary return to two-lung ventilation is appropriate for severe hypoxemia. Communicate early with the surgeon, particularly before reinflating the operative lung. In selected cases, clamping the pulmonary artery during pneumonectomy or addressing a major shunt source can improve oxygenation, but those are procedure-specific decisions.

At the end of OLV, reinflate the operative lung under direct communication with the surgeon and avoid unnecessarily high airway pressures. Assess for air leak, bleeding, residual blockade, and postoperative ventilation needs. Patients at high risk for postoperative pulmonary complications benefit from multimodal analgesia, early mobilization, and strategies that permit effective cough and deep breathing.

Epidemiology / Risk Factors

• OLV is routine in thoracic anesthesia for lung resection, esophageal surgery, and selected minimally invasive procedures.
• Hypoxemia remains one of the most common intraoperative challenges during OLV.
• Modern practice has shifted away from large tidal volumes toward lung-protective ventilation.
• Postoperative pulmonary complications are influenced by both intraoperative ventilation and patient and surgical factors.

Investigations

Hypoxemia Steps

Pharmacology

Prognosis / Complications

• Most OLV-associated desaturation resolves after correcting device position, recruitment, PEEP, or shunt management.
• Persistent severe hypoxemia is uncommon but can require interruption of surgery.
• Excessive airway pressure and injurious ventilation increase postoperative pulmonary risk.
• Effective analgesia and early postoperative pulmonary care improve recovery after thoracic procedures.

Patient Education / Counseling

• Explain to patients that lung isolation is a standard part of many thoracic operations.
• Discuss the possibility of postoperative oxygen, chest tubes, or temporary ventilatory support based on the planned surgery.
• Encourage smoking cessation and preoperative pulmonary optimization when time allows.
• Describe the role of regional or multimodal analgesia in helping deep breathing and coughing after surgery.
• Patients with severe underlying lung disease should understand that postoperative respiratory support may be more likely.

Notes

The most dangerous response to OLV hypoxemia is escalating ventilator pressure without first confirming the lung-isolation device. A migrated double-lumen tube can obstruct a lobe or partially ventilate the wrong lung, and bronchoscopy often identifies a quickly reversible problem.

Ventilation targets should be individualized to the patient and operation. Low tidal volume is one component of lung protection; driving pressure, PEEP, recruitment, oxygen exposure, fluid balance, and surgical factors also matter.

References

1. BJA Education: Hypoxaemia During One Lung Ventilation — Link
2. BJA Education: Causes and Management of Impaired Gas Exchange in Thoracic Surgery — Link