What is the role of high flow nasal canula (HFNC) in managing patients with hydropneumothorax?

High Flow Nasal Cannula in Hydropneumothorax

Direct Answer

HFNC is contraindicated in hydropneumothorax and should not be used. The positive end-expiratory pressure (PEEP) effect generated by HFNC (approximately 2-5 cmH2O at flows of 50-60 L/min) can worsen pneumothorax by increasing intrathoracic pressure and preventing lung re-expansion 1, 2.

Physiological Rationale for Contraindication

The mechanism of HFNC directly conflicts with the pathophysiology of pneumothorax:

• HFNC delivers high flow rates (up to 60 L/min) that create positive airway pressure, which can force additional air into the pleural space through any existing bronchopleural communication 1, 2
• The PEEP effect of 2-5 cmH2O generated at standard HFNC flows increases the pressure gradient favoring air leak into the pleural cavity 1
• This positive pressure can prevent spontaneous pneumothorax resolution and may convert a simple pneumothorax into a tension pneumothorax 2

Appropriate Management Algorithm

Step 1: Immediate Assessment and Stabilization

• Secure the airway and provide conventional oxygen therapy (COT) via facemask or nasal cannula at flows ≤6 L/min to avoid positive pressure 3
• Assess pneumothorax size and hemodynamic stability
• Determine if immediate chest tube placement is required

Step 2: Definitive Treatment of Pneumothorax

• Place chest tube for drainage of both air and fluid components before considering any form of positive pressure respiratory support 2
• Confirm lung re-expansion with chest radiography
• Ensure no persistent air leak through the chest tube system

Step 3: Respiratory Support Selection After Pneumothorax Resolution

• Once the pneumothorax is fully resolved (confirmed radiographically) and the chest tube is removed, HFNC may be reconsidered if hypoxemic respiratory failure persists 3
• If hypoxemia requires immediate support while pneumothorax is still present, use COT with close monitoring 3
• NIV is also contraindicated until pneumothorax is completely resolved due to similar positive pressure concerns 1

Critical Pitfalls to Avoid

Never initiate HFNC in the presence of untreated pneumothorax:

• The comfort and ease of use of HFNC should not override the absolute contraindication in pneumothorax 3, 2
• Even small pneumothoraces can rapidly progress to tension pneumothorax under positive pressure 2
• The improved oxygenation seen with HFNC (mean PaO2 increase of 16.72 mmHg) does not justify the risk of pneumothorax expansion 3

Do not delay definitive pneumothorax treatment:

• Attempting to manage hypoxemia with any form of positive pressure before addressing the pneumothorax can be life-threatening 2
• The reduced work of breathing and patient comfort associated with HFNC are irrelevant if the underlying pneumothorax worsens 3, 2

Alternative Respiratory Support Options

While pneumothorax is present:

• Use COT with reservoir masks to achieve FiO2 up to 60-80% without generating positive pressure 3
• Consider high-flow oxygen via non-rebreather mask (10-15 L/min) as this does not generate the same PEEP effect as HFNC 3
• If severe hypoxemia persists despite COT and chest tube placement, proceed directly to intubation and mechanical ventilation with careful attention to ventilator settings to minimize barotrauma 4

After complete pneumothorax resolution:

• HFNC may be used for post-operative respiratory support if the patient underwent thoracic surgery for hydropneumothorax treatment, though evidence suggests either HFNC or COT are reasonable options 3
• For high-risk post-operative patients, either HFNC or NIV may be considered, with HFNC offering the advantage of reduced skin breakdown compared to NIV 3