What is a reasonable starting point for Positive End-Expiratory Pressure (PEEP) in a ventilator for lung recruitment?

Optimal PEEP Settings for Lung Recruitment in Mechanical Ventilation

For initial lung recruitment, a PEEP setting of 5-8 cmH2O is recommended as a starting point, with subsequent titration based on the patient's underlying condition and response to ventilation. 1

Initial PEEP Settings Based on Clinical Scenario

General Starting Points

• Healthy lungs: 5-10 cmH2O 1, 2
• Mild respiratory failure: 5-10 cmH2O 2
• Moderate respiratory failure: 10-15 cmH2O 2, 3
• Severe respiratory failure/ARDS: 15-20 cmH2O 2, 3

Patient-Specific Considerations

• Pediatric patients: 5-8 cmH2O, with higher PEEP necessary based on disease severity 1
• Cardiac patients: Same principles apply as for non-cardiac patients, with PEEP up to 15 cmH2O not impairing venous return or cardiac output 1
• Obstructive airway disease: Add PEEP to stent airways and facilitate triggering 1
• Obese patients: Higher PEEP (10-15 cmH2O) may be required to overcome increased chest wall resistance 1

PEEP Titration Strategy

1. Start with 5 cmH2O PEEP and tidal volume of 6-8 mL/kg predicted body weight 1

2. Monitor key parameters:

   • Plateau pressure (keep ≤30 cmH2O) 1, 2
   • Driving pressure (Pplat-PEEP, keep ≤15 cmH2O) 1
   • Oxygenation (target SpO2 92-97% for most patients) 2
   • Hemodynamic stability (watch for hypotension with higher PEEP) 2

3. Increase PEEP in increments of 2-3 cmH2O while monitoring:

   • Improvement in oxygenation
   • Changes in compliance
   • Hemodynamic effects
   • Driving pressure (should not increase)

Recruitment Maneuvers

When performing recruitment maneuvers to complement PEEP:

1. Stepwise recruitment is preferred over sustained inflation 3
2. Pressure control recruitment maneuver (PCRM) with PEEP of 15 cmH2O and pressure control above PEEP of 35 cmH2O for 2 minutes has shown better results than continuous positive airway pressure recruitment maneuver (CRM) 1
3. Monitor ICP closely if the patient has neurological injury, as recruitment maneuvers may increase intracranial pressure 1

Special Considerations

Neurological Injury

• In patients with acute brain injury, PEEP up to 20 cmH2O may be used without significant effects on ICP during early phases, but monitor closely, especially around day 7 post-injury 1
• For patients with severe lung injury (PaO2/FiO2 < 100) and neurological injury, each 1 cmH2O increase in PEEP may increase ICP by 0.31 mmHg 1

ARDS

• Higher PEEP levels (>10 cmH2O) have shown mortality benefit in moderate to severe ARDS (PaO2/FiO2 ≤ 200 mmHg) 1
• Consider PEEP based on severity: 5-10 cmH2O for mild ARDS, 10-15 cmH2O for moderate ARDS, and 15-20 cmH2O for severe ARDS 3

Spontaneously Breathing Patients

• In patients on CPAP/PS mode, recruitment maneuvers with 40 cmH2O of pressure support for 40 seconds can improve oxygenation in approximately 50% of patients 4

Monitoring Response to PEEP

• Positive response: Improved oxygenation, stable or improved compliance, stable hemodynamics
• Negative response: Decreased oxygenation, decreased compliance, hemodynamic compromise, increased dead space to tidal volume ratio 4

Practical Algorithm for PEEP Titration

1. Assess severity of respiratory failure
2. Start with 5 cmH2O PEEP and 6-8 mL/kg PBW tidal volume
3. Increase PEEP by 2-3 cmH2O increments
4. After each increment, wait 15-20 minutes and assess:
   • If oxygenation improves and driving pressure decreases or remains stable → continue titration
   • If oxygenation worsens or driving pressure increases → return to previous PEEP level
   • If hemodynamics deteriorate → decrease PEEP
5. Optimal PEEP is the level that balances recruitment against overdistention 3

Common Pitfalls to Avoid

• Setting PEEP too low: Can lead to atelectrauma from repetitive opening and closing of alveoli 5
• Setting PEEP too high: Can cause overdistention, hemodynamic compromise, and increased dead space 4
• Ignoring driving pressure: Focus on keeping driving pressure ≤15 cmH2O rather than just absolute PEEP values 1
• Relying solely on oxygenation: Oxygenation alone may not reflect optimal PEEP for lung protection 6
• Not individualizing PEEP: The "one-size-fits-all" approach may not be optimal for all patients 6

By following these guidelines and carefully monitoring patient response, PEEP can be optimized to improve oxygenation while minimizing the risk of ventilator-induced lung injury.