Bronchopleural Fistulae

Air leak occurring between airways and the pleural space, and are divided into:

Alveolar/parenchymal-pleural
Bronchopleural
From the tracheobronchial tree.
- Typically presents with persistent pneumothorax or immediate large air leak

Epidemiology and Risk Factors

Pathophysiology

Physiological effects depend on:

Presence of ICC
- In absence of an ICC, the pleural pressure will equalise with atmospheric and the lung will collapse under its own elastic recoil
  - A tension pneumothorax may develop if the fistula behaves as a one-way valve
- An ICC will demonstrate continuous air leak, and the lung may only partially reinflate (if at all)
Size of fistulae
- Large fistulae lead to preferential flow via fistulae and reduction in:
  - Alveolar ventilation
  - FRC

Alteration in lung function:

Lung collapse and subsequent hypoxic pulmonary vasoconstriction tend to limit shunt, and hypoxia is not a common feature of uncomplicated fistula
Dead space leads to respiratory acidosis
↑ work of breathing due to requirement to generate a more negative intrapleural pressure m
Decrecruitment of unaffected lung due to failure to maintain auto-PEEP

Aetiology

Alveolar/parenchymal-pleural:

Pulmonary disease
- COAD
- Infections
- Tumour
Iatrogenic
- Volutrauma
  Note that alveolar do not tend to rupture through the pleural membrane, and instead air dissects along bronchovascular sheaths to the mediastinum. Pneumomediastinum then further dissects to create subcutaneous emphysema or pneumothorax.
- Radiotherapy

Bronchopleural:

Trauma
- Penetrating
- Blunt
  - Overpressure with a closed glottis
    Usually causes rupture within 2cm of carina.
  - Rapid A-P compression
  - Acceleration-deceleration injury
    Traction of lungs against a fixed carina.
Iatrogenic
Common post thoracic surgery.

Clinical Manifestations

Respiratory:

Acidosis
↑ work of breathing
- Air hunger
- Dyspnoea
- Tachypnoea

Diagnostic Approach and DDx

Investigations

Management

Medical

Surgical

Anaesthetic Considerations

B
- ICC placed and patent
  - Obstructed ICC will lead to tension pneumothorax with IPPV
  - Chest drain should be large enough to adequately ventilate pleural space
    32Fr ICC is large enough to drain up to 15L/min of fistula flow on 10cmH₂O of suction.
  - If drain has been on suction on the ward, continue suction during anaesthetic induction
- Effective size of fistulae
  Combination of physical size and effect on distribution of ventilation and fistulae gas flow.
  - Determines effect of positive pressure ventilation on fistulae flow
  - Compliant lungs and a small fistula favours pulmonary ventilation
  - Non-compliant lungs and a large fistula favours fistula flow
    This leads to inadequate alveolar ventilation.
  - ↑ size of fistula suggested by:
    - Respiratory distress
    - Volume of gas draining
      - Only with coughing Suggests small or trivial.
      - Expiration only
        Suggests moderate size.
      - Inspiration and expiration
        Suggests large.
    - Imaging
      - Complete ipsilateral lung collapse despite ICC and suction
- Induction strategies
  - Small fistulae are amenable to conventional induction
  - Large fistulae require maintenance of spontaneous ventilation until fistulae isolation
    - Reduction in FRC and difficulty effectively ventilating the patient can occur when initiating IPPV
    - Spontaneously ventilating induction required to maintain alveolar ventilation
      - Volatile or propofol infusion and DLT or SLT
        
        Consider a small dose of midazolam with induction
        
        Consider gentle pressure support
        
        Topicalise with 10-15ml 2% lignocaine to mouth and tracheobronchial tree
        
        Consider propofol (0.5mg/kg) or short-acting opioid (alfentanil 10-15μg/kg) prior to laryngoscopy
        Noting possibility for apnoea.
        
        Place airway device into proximal trachea
        
        Advance tube under bronchoscopic vision
      - Awake intubation with SLT and endobronchial intubation or blocker

Marginal and Ineffective Therapies

Complications

Death

Infection:

Empyema