In patients with pneumothorax, which ventilator settings, PEEP (Positive End-Expiratory Pressure) or FiO2 (Fraction of Inspired Oxygen), should be prioritized to be high?

Ventilator Settings in Pneumothorax: FiO2 Should Be High, PEEP Should Be Minimized

In patients with pneumothorax requiring mechanical ventilation, FiO2 should be prioritized to be high (targeting 15 L/min via reservoir mask or equivalent high-concentration oxygen), while PEEP should be kept as low as safely possible to avoid worsening the pneumothorax. 1

Rationale for High FiO2

High-concentration oxygen (15 L/min via reservoir mask, delivering 60-90% FiO2) accelerates pneumothorax reabsorption by up to four times faster than ambient air by reducing the partial pressure of nitrogen in pleural capillaries and increasing the pressure gradient for air absorption. 1 This increases reabsorption from 1.25-1.8% of hemithorax volume per day to approximately 4.2% per day. 1

• The British Thoracic Society specifically recommends administering oxygen at high flow (10-15 L/min) to hospitalized patients with pneumothorax under observation. 1
• Target oxygen saturation should be 94-98% in patients without risk of hypercapnic respiratory failure. 1

Important Caveat for COPD Patients

• Exercise caution in patients with COPD or other risk factors for hypercapnic respiratory failure (severe chest wall disease, neuromuscular disease, severe obesity, cystic fibrosis, bronchiectasis), as they may require lower oxygen concentrations with a target saturation of 88-92%. 1
• In these high-risk patients, initiate oxygen at 28% or 24%, or 1-2 L/min via nasal cannula, and obtain arterial blood gases to guide adjustments. 1

Rationale for Low PEEP

PEEP should be minimized in pneumothorax because positive pressure can worsen air leak and expand the pneumothorax. 2

• The Cystic Fibrosis Foundation guidelines explicitly recommend that positive expiratory pressure (PEP) therapies should not be used in patients with pneumothorax, particularly in large pneumothoraces. 2
• Setting PEEP greater than intrinsic PEEP (iPEEP) can be harmful in patients with airflow obstruction. 2

Ventilator Strategy in Mechanically Ventilated Patients with Pneumothorax

When mechanical ventilation is unavoidable:

• Use lung-protective ventilation strategies with low tidal volumes (6-8 mL/kg) and low airway pressures. 2
• Maintain PEEP >10 cmH2O only when necessary to prevent atelectasis in post-cardiac arrest or ARDS patients, but this recommendation does not apply to isolated pneumothorax. 2
• Limit peak airway pressures and avoid excessive PEEP escalation in non-recruitable lungs to prevent structural failure and worsening pneumothorax. 3
• Consider pressure-controlled ventilation with prolonged expiratory time to reduce dynamic hyperinflation. 2

Clinical Monitoring Algorithm

1. Initiate high-flow oxygen (15 L/min via reservoir mask) unless contraindicated by COPD/hypercapnic risk. 1
2. If mechanical ventilation is required, use minimal PEEP necessary for oxygenation (typically 5 cmH2O or less). 2
3. Monitor for signs of tension pneumothorax: acute desaturation, hypotension, tachycardia, reduced minute ventilation, rising airway pressures. 3
4. Obtain chest tube placement if patient is symptomatic or on mechanical ventilation. 4
5. Use bedside ultrasound for rapid diagnosis if clinical deterioration occurs, as it outperforms supine radiography. 3

Critical Warning

Never withhold oxygen therapy to obtain room air measurements in patients who clearly require oxygen. 1 Pneumothorax under positive-pressure ventilation can present within hours of intubation and requires immediate recognition and decompression. 3