What ventilator settings should be used for a patient with a bronchopleural fistula who requires mechanical ventilation?

Mechanical Ventilation Settings for Bronchopleural Fistula

Use lung-protective ventilation with the lowest possible peak inspiratory pressures (PIP), minimize or avoid PEEP (keep ≤5 cm H₂O), reduce tidal volumes to 4-6 mL/kg predicted body weight, shorten inspiratory time, and decrease respiratory rate to minimize air leak through the fistula. 1

Understanding the Physiology

The fundamental principle driving ventilator management in bronchopleural fistula (BPF) is that air follows the path of least resistance—preferentially escaping through the fistula rather than ventilating functional lung tissue. 1 The driving pressure across the BPF (the difference between airway pressure and pleural pressure) determines the magnitude of air leak. 1, 2

PEEP has a dramatically greater impact on fistula flow than peak inspiratory pressure. Animal studies demonstrate that PEEP increases air leak by over sixfold compared to equivalent increases in PIP. 3 Specifically, any PEEP >6 cm H₂O causes more air loss than any level of PIP tested. 3

Initial Ventilator Settings

Start with volume-cycled assist-control (AC) ventilation as your initial mode: 4

• Tidal volume: 4-6 mL/kg predicted body weight (calculate using: Men = 50 + 2.3 × [height in inches - 60]; Women = 45.5 + 2.3 × [height in inches - 60]) 4, 1
• PEEP: 0-5 cm H₂O maximum 1, 3
• Peak inspiratory pressure: Keep as low as possible while maintaining adequate ventilation 1
• Respiratory rate: Minimize to reduce minute ventilation through the fistula 1
• Inspiratory time: Shorten to decrease the duration of positive pressure exposure 1
• Plateau pressure: Target <30 cm H₂O 4

Chest Tube Management

The pleural drainage system must be optimized to minimize negative intrapleural pressure, which increases the transpulmonary pressure gradient and worsens air leak: 1

• Use water seal without suction initially 5, 1
• If suction is absolutely necessary, use the lowest level possible 1
• Consider adding controlled positive pressure to the pleural space (via the chest tube system) to decrease the expiratory transpulmonary pressure difference and reduce fistula flow 2
• Monitor for tension pneumothorax if reducing suction 1

Permissive Hypercapnia Strategy

Accept higher PaCO₂ levels (permissive hypercapnia) rather than increasing minute ventilation, which would worsen air leak: 1

• Tolerate PaCO₂ up to 60-70 mmHg if pH remains >7.20 1
• Prioritize oxygenation (SpO₂ ≥88-90%) over normocapnia 1
• Avoid aggressive ventilation that increases PIP or respiratory rate 1

Alternative Ventilator Modes

If conventional ventilation fails, consider these options in sequence:

High-Frequency Oscillatory Ventilation (HFOV)

HFOV can be effective when conventional positive pressure ventilation fails with high-output BPF. 6 HFOV uses very low tidal volumes (1-2 mL/kg) at high frequencies (3-15 Hz), which may reduce air leak while maintaining gas exchange. 6 However, animal studies show HFOV does not consistently reduce fistula flow compared to conventional ventilation when PEEP is increased. 7

Airway Pressure Release Ventilation (APRV)

APRV may be considered for refractory hypoxemia, though it typically uses higher mean airway pressures which could theoretically worsen BPF leak. 8 Use cautiously and monitor air leak closely. 8

Independent Lung Ventilation

For large, persistent BPF, consider lung isolation with a double-lumen endotracheal tube or bronchial blocker: 1

• Allows separate ventilation of each lung 1
• Apply minimal or no PEEP to the affected side 1
• Use conventional lung-protective ventilation on the unaffected side 1
• Requires expertise in placement and management 1

Rescue Therapies for Refractory Cases

When ventilator adjustments fail to maintain adequate gas exchange:

Extracorporeal Membrane Oxygenation (ECMO)

Consider ECMO when PaO₂/FiO₂ <100 mmHg despite optimized settings, or when pH <7.15 with excessive respiratory acidosis, or when plateau pressure >30 cm H₂O cannot be avoided. 9, 1 ECMO allows near-apneic ventilation, dramatically reducing air leak and allowing fistula healing. 1

Bronchoscopic Interventions

Endobronchial placement of one-way valves or occlusion devices can reduce or eliminate air leak while maintaining ventilation of unaffected segments. 1 This requires interventional pulmonology expertise. 1

Critical Pitfalls to Avoid

• Never use high PEEP (>5 cm H₂O) in BPF—this is the single most important factor increasing air leak 3
• Do not apply suction to chest tubes unless absolutely necessary—negative pleural pressure worsens the transpulmonary gradient 1, 2
• Avoid high respiratory rates and prolonged inspiratory times—these increase cumulative positive pressure exposure 1
• Do not target normocapnia aggressively—accept permissive hypercapnia to minimize ventilation 1
• Monitor for tension pneumothorax when reducing chest tube suction—ensure adequate pleural drainage 1

Monitoring Parameters

Track these variables to assess response and guide adjustments:

• Fistula flow volume (measured at chest tube): Goal is progressive reduction 1
• Peak and plateau airway pressures: Keep as low as possible 1
• Arterial blood gases: Accept PaCO₂ 50-70 mmHg if pH >7.20 1
• Chest radiograph: Monitor for pneumothorax expansion or lung re-expansion 1
• Hemodynamics: Watch for cardiovascular compromise from altered intrathoracic pressures 1