In what conditions should Positive End-Expiratory Pressure (PEEP) be kept low or high?

PEEP Management in Different Respiratory Conditions

PEEP should be kept low in obstructive airway diseases and high in restrictive lung diseases, with careful titration based on the underlying pathophysiology to optimize outcomes. 1, 2

Obstructive Airway Diseases (COPD, Asthma)

Low PEEP Strategy

• Keep PEEP low (3-5 cmH2O) in patients with obstructive airway diseases 1
• Rationale: Higher PEEP may worsen air trapping and dynamic hyperinflation, leading to:
  • Increased work of breathing
  • Hemodynamic compromise due to decreased venous return
  • Patient-ventilator asynchrony

Special Considerations for Obstructive Disease

• Auto-PEEP management: In patients with intrinsic PEEP (auto-PEEP), external PEEP may be set to offset the inspiratory threshold load, but should not exceed intrinsic PEEP 1, 3
• Optimal approach: Set external PEEP at approximately 80% of measured intrinsic PEEP 3, 4
• Warning: Setting PEEP greater than intrinsic PEEP can be harmful by worsening hyperinflation 1
• Monitoring: Assess for signs of increased air trapping (rising plateau pressures, decreased compliance, hemodynamic compromise) 1

Restrictive Lung Diseases (ARDS, Pulmonary Edema)

High PEEP Strategy

• Use higher PEEP (>10 cmH2O) in moderate to severe ARDS 1, 2
• Rationale: Higher PEEP helps with:
  • Alveolar recruitment
  • Prevention of atelectrauma
  • Improved compliance
  • Better oxygenation

PEEP Titration in ARDS

• Mild ARDS (PaO2/FiO2 201-300 mmHg): Lower PEEP (5-10 cmH2O) 2
• Moderate ARDS (PaO2/FiO2 101-200 mmHg): Higher titrated PEEP 1, 2
• Severe ARDS (PaO2/FiO2 ≤100 mmHg): Higher titrated PEEP with consideration of prone positioning 1, 2

Recruitment Maneuvers

• Higher PEEP strategies should be considered as part of lung recruitment in severe hypoxemia 1
• Caution: Monitor hemodynamics closely as higher PEEP can compromise cardiac output 1

Neuromuscular Disease & Chest Wall Disorders

• Use moderate PEEP (10-15 cmH2O) in neuromuscular diseases 1
• Use higher PEEP in chest wall disorders due to reduced chest wall compliance 1
• Rationale: Helps overcome the restrictive physiology and prevent small airway closure 1

Monitoring and Titration Approach

Parameters to Monitor

• Oxygenation: PaO2/FiO2 ratio or SpO2
• Ventilation: PaCO2, pH
• Mechanics: Plateau pressure, driving pressure, compliance
• Hemodynamics: Blood pressure, cardiac output

PEEP Titration Algorithm

1. Start with physiologic PEEP (3-5 cmH2O) in patients without lung injury 1
2. Assess underlying pathophysiology (obstructive vs. restrictive)
3. For obstructive disease:
   • Measure intrinsic PEEP
   • Set external PEEP below intrinsic PEEP
   • Monitor for worsening hyperinflation
4. For restrictive disease:
   • Start with moderate PEEP (8-10 cmH2O)
   • Titrate up based on oxygenation response
   • Target plateau pressure <30 cmH2O 1
   • Consider PEEP/FiO2 tables for ARDS patients 1

Special Clinical Scenarios

Post-Cardiac Arrest

• Avoid hyperventilation and excessive PEEP that may compromise venous return 1
• Target normocapnia (PaCO2 40-45 mmHg) 1

Pediatric Patients

• Physiologic PEEP (3-5 cmH2O) is appropriate for children without lung injury 1
• Higher PEEP may be needed in severe disease 1
• Balance between hemodynamics and oxygenation is crucial 1

Obesity and Pregnancy

• Higher PEEP may be beneficial to overcome decreased functional residual capacity 2
• Monitor driving pressure closely to minimize risk of lung injury 2

Pitfalls to Avoid

• Setting PEEP greater than intrinsic PEEP in obstructive diseases, which worsens hyperinflation 1
• Using low PEEP in severe ARDS, which may lead to atelectrauma and worsened oxygenation 1
• Ignoring hemodynamic effects of high PEEP, particularly in hypovolemic patients 1
• Failing to reassess PEEP requirements as the patient's condition changes 1

By carefully selecting appropriate PEEP levels based on the underlying pathophysiology and monitoring patient response, clinicians can optimize ventilation strategies to improve outcomes in mechanically ventilated patients.