Nitrogen Washout for Pneumothorax Treatment
High-flow oxygen therapy (10-15 L/min via reservoir mask) should be administered to accelerate pneumothorax reabsorption through nitrogen washout, as this increases the reabsorption rate approximately 3-4 fold compared to breathing room air alone. 1, 2, 3
Mechanism of Nitrogen Washout
The principle behind nitrogen washout therapy relies on creating a diffusion gradient that accelerates air reabsorption from the pleural space. 3
Breathing 100% oxygen replaces nitrogen in the blood, creating a steep concentration gradient between the nitrogen-rich air in the pleural space and the nitrogen-depleted blood, which dramatically accelerates reabsorption. 3
The reabsorption rate increases from 1.25-1.8% of hemithorax volume per day on room air to approximately 4.2% per day with high-flow oxygen, representing more than a three-fold acceleration. 2, 3
This effect is most pronounced in smaller pneumothoraces (<30% of hemithorax volume), where oxygen therapy can reduce the pneumothorax to one-third of its original size within the first 72 hours. 3
Practical Implementation
Administer high-concentration oxygen at 10-15 L/min via a reservoir (non-rebreather) mask to achieve the nitrogen washout effect. 1, 2
The British Thoracic Society specifically recommends 10 L/min as the standard flow rate for pneumothorax management. 1
Alternative protocols suggest 15 L/min via reservoir mask for patients without contraindications to maximize the washout effect. 2
Target oxygen saturation of 94-98% in patients without risk factors for hypercapnic respiratory failure. 2
Reduce target to 88-92% in patients with COPD or other conditions predisposing to CO2 retention. 2
Clinical Application Algorithm
For small primary pneumothorax (<3 cm apex-to-cupola distance) with minimal symptoms:
- Observation with high-flow oxygen therapy (10 L/min) is appropriate as first-line management. 1, 3
- This approach is particularly effective when the pneumothorax is less than 30% of hemithorax volume. 3
For symptomatic or larger pneumothoraces:
- High-flow oxygen should be used as an adjunct to definitive interventions (aspiration or chest tube drainage), not as sole therapy. 1
- Pneumothoraces greater than 30% typically require invasive drainage procedures despite oxygen therapy. 3
For secondary pneumothorax or patients with underlying lung disease:
- High-flow oxygen remains beneficial but should accompany more aggressive intervention (chest tube drainage). 1
Critical Monitoring Parameters
Monitor the following at least twice daily during oxygen therapy: 2
- Oxygen saturation via pulse oximetry
- Respiratory rate (tachypnea may indicate worsening)
- Heart rate (tachycardia is an early sign of hypoxemia)
- Mental status changes
Obtain arterial blood gases in critically ill patients or those with unexpected drops in SpO2 below 94% to assess for hypercapnia. 2
Important Caveats and Pitfalls
Avoid using high-flow nasal cannula (HFNC) systems in patients with existing pneumothorax, as the positive pressure may worsen the condition; standard reservoir masks are preferred. 2
Do not rely on oxygen therapy alone for pneumothoraces >30% of hemithorax volume, as these consistently require invasive drainage despite supplemental oxygen. 3
Patients with COPD require careful monitoring during high-flow oxygen therapy due to risk of hypercapnic respiratory failure; maintain lower saturation targets (88-92%). 2
Continue oxygen therapy throughout hospitalization until radiographic resolution is confirmed, as premature discontinuation will slow reabsorption back to baseline rates. 1, 3