Can Positive End-Expiratory Pressure (PEEP) cause blebs and tension pneumothorax?

Can PEEP Cause Blebs and Tension Pneumothorax?

PEEP itself does not cause blebs (which are pre-existing structural lung abnormalities), but positive pressure ventilation including PEEP can cause pneumothorax and tension pneumothorax through barotrauma, particularly in patients with underlying lung disease or when excessive airway pressures are used. 1, 2

Understanding the Mechanism

PEEP and Barotrauma Risk

• Barotrauma from positive pressure ventilation (including PEEP) represents a well-documented complication that can lead to pneumothorax, pneumomediastinum, and interstitial emphysema, particularly when high airway pressures are employed 2

• High peak inspiratory pressures resulting from positive-pressure ventilation can lead to pneumothorax, especially in patients with severe bronchoconstriction or underlying lung pathology 1

• The risk is substantially increased when plateau pressures exceed 30 cm H₂O in mechanically ventilated patients 1

Auto-PEEP: A Critical Distinction

• Auto-PEEP (intrinsic PEEP) develops from breath stacking during positive-pressure ventilation when expiratory time is insufficient, leading to hyperinflation and increased risk of tension pneumothorax 1, 3

• Auto-PEEP can develop during mechanical ventilation with severe bronchoconstriction, creating complications such as hyperinflation, tension pneumothorax, and hypotension 1

• This is particularly problematic in asthma and COPD patients where airflow limitation prevents complete exhalation 1, 3, 4

Clinical Context: Blebs vs. Barotrauma

Pre-existing Blebs

• Blebs are pre-existing structural abnormalities (often associated with COPD or emphysema) that may rupture when exposed to positive pressure ventilation, not caused by PEEP itself 5

• Chronic obstructive pulmonary disease may cause blebs or bullae, which might rupture when exposed to positive pressure ventilation of any kind 5

PEEP-Related Pneumothorax

• Tension pneumothorax is a rare but life-threatening complication of mechanical ventilation, though it usually occurs in patients already receiving positive pressure support 1

• While tension pneumothorax usually occurs in patients receiving mechanical ventilation, cases in spontaneously breathing patients have been reported 1

Risk Mitigation Strategies

Ventilator Settings to Minimize Risk

• Target tidal volumes of 6 mL/kg predicted body weight in patients with ARDS to minimize barotrauma risk 1

• Maintain plateau pressures ≤ 30 cm H₂O in passively inflated lungs 1

• Use lower respiratory rates with smaller tidal volumes (6-8 mL/kg) and longer expiratory times (I:E ratio 1:4 or 1:5) in patients with severe bronchoconstriction to prevent auto-PEEP 1, 3

Appropriate PEEP Application

• PEEP should be applied to avoid alveolar collapse (atelectotrauma), which is its primary therapeutic purpose 1

• In patients with moderate or severe ARDS, higher PEEP levels (versus lower) are recommended without significantly increasing barotrauma risk when used with lung-protective ventilation 1

• Evidence shows that high PEEP may result in little to no difference in barotrauma compared to low PEEP when used appropriately (RR 1.00,95% CI 0.64-1.57) 6

Managing Auto-PEEP to Prevent Complications

• Decrease respiratory rate or tidal volume to minimize auto-PEEP development 1, 3

• If auto-PEEP results in significant hypotension, briefly disconnect from the ventilator circuit to allow PEEP to dissipate during passive exhalation 1, 4

• Assist with exhalation by pressing on the chest wall after disconnection if severe hypotension occurs 1, 4

Diagnostic Approach When Pneumothorax is Suspected

Clinical Recognition

• Use the DOPE mnemonic (tube Displacement, tube Obstruction, Pneumothorax, Equipment failure) plus auto-PEEP when evaluating acute deterioration in mechanically ventilated patients 1, 4

• Sudden hypotension or cardiovascular collapse in mechanically ventilated patients with obstructive airway disease suggests significant auto-PEEP or tension pneumothorax 4

Critical Caveat

• If tension pneumothorax is suspected in a hemodynamically unstable patient, treat clinically immediately rather than delaying for diagnostic confirmation, particularly when the provider is not an expert sonographer 1

• High airway pressures and difficulty ventilating are more commonly due to auto-PEEP and hyperinflation rather than pneumothorax in patients with severe asthma, but pneumothorax must still be ruled out 1

Key Clinical Pitfalls

• Do not confuse therapeutic PEEP with auto-PEEP: Therapeutic PEEP at appropriate levels does not substantially increase pneumothorax risk, while auto-PEEP from inadequate expiratory time significantly increases this risk 1, 3, 6

• Low levels of external PEEP (5-10 cm H₂O) can actually be beneficial in patients with auto-PEEP by counterbalancing intrinsic PEEP and reducing work of breathing, without substantially increasing hyperinflation hazards 7, 4

• Never set external PEEP levels in excess of intrinsic PEEP, as this can worsen hyperinflation and cause hemodynamic compromise 4