When to Apply PEEP in Mechanically Ventilated Patients
PEEP should be applied to ALL mechanically ventilated patients at a minimum of 5 cm H₂O, with higher levels (10-15 cm H₂O) specifically indicated for moderate-to-severe ARDS (PaO₂/FiO₂ <200 mmHg). 1
Universal Baseline PEEP Application
Apply PEEP 5 cm H₂O as the standard minimum for every mechanically ventilated patient, regardless of underlying condition. 1 This baseline prevents lung derecruitment, atelectasis, and cyclic alveolar collapse that occurs with zero PEEP. 1 The 5 cm H₂O minimum ameliorates changes in closing volume and often provides dramatic improvements in oxygenation. 1
Zero PEEP (ZEEP) is explicitly contraindicated in any mechanically ventilated patient, as it leads to alveolar collapse and decreased oxygenation. 1
PEEP Titration Based on ARDS Severity
The approach to PEEP differs dramatically based on the severity of respiratory failure:
Moderate-to-Severe ARDS (PaO₂/FiO₂ <200 mmHg)
Use higher PEEP levels of 10-15 cm H₂O in patients with moderate-to-severe ARDS. 2, 1 Individual patient data meta-analysis demonstrated mortality reduction with higher PEEP (mean 15.1 ± 3.6 cm H₂O) versus lower PEEP (mean 9.1 ± 2.7 cm H₂O) specifically in this subgroup, with an adjusted relative risk for mortality of 0.90 (95% CI, 0.81-1.00). 1 Higher PEEP strategies in this population help maximize alveolar recruitment, improve lung homogeneity, and reduce atelectrauma from repeated opening and closing of alveoli. 2
Consider recruitment maneuvers before PEEP selection in severe refractory hypoxemia, though these should be used as rescue measures rather than routine interventions. 2, 3
Mild ARDS (PaO₂/FiO₂ 200-300 mmHg)
Use lower PEEP (<10 cm H₂O) for mild ARDS, as higher PEEP showed no mortality benefit and potential harm in this subgroup. 1, 4 The meta-analysis data suggest that mortality may actually be higher with aggressive PEEP strategies in less severe hypoxemia. 5 Lower PEEP in this population avoids impairing venous return and cardiac preload without sacrificing outcomes. 4
Critical Safety Parameters During PEEP Application
Regardless of PEEP level selected, always maintain plateau pressure ≤30 cm H₂O to prevent lung injury and improve outcomes. 2, 1 Measure plateau pressure with each ventilator adjustment using an end-inspiratory pause of 0.3-0.5 seconds. 4
Target driving pressure (plateau pressure minus PEEP) <15 cm H₂O, as this predicts outcomes better than any other ventilatory parameter. 2, 1 When applied with constant tidal volume, PEEP simultaneously reduces the number of lung units exposed to stress but increases stresses on those already open. 2 Driving pressure accounts for this relationship and reflects the "functional" size of the lung available for ventilation. 2
PEEP Application in Specific Clinical Scenarios
Sepsis-Related Respiratory Failure
Apply PEEP to maintain oxygen saturation approximately 88-90% (PaO₂ ~60 mmHg) with FiO₂ ideally <0.60. 1 Consider higher PEEP with recruitment maneuvers during times of rapid respiratory system compliance changes. 1
Intraoperative Mechanical Ventilation
Set initial PEEP at 5 cm H₂O for all surgical patients undergoing mechanical ventilation. 1 Consider higher PEEP with recruitment maneuvers during times of rapid respiratory system compliance changes. 1
Pediatric Patients
Use PEEP 3-5 cm H₂O in children without lung injury. 1 Higher PEEP may be needed in severe pediatric ARDS, but careful titration is mandatory to avoid cardiovascular compromise. 1
Common Pitfalls to Avoid
Do not apply high PEEP strategies (≥10 cm H₂O) routinely in mild ARDS or non-ARDS respiratory failure, as this can impede venous return and worsen hemodynamics without clear benefit. 4 The severity of hypoxemia correlates with the amount of lung recruitability—patients with less severe disease have less recruitable lung and therefore less benefit from aggressive PEEP. 5
Do not use zero PEEP in any mechanically ventilated patient. 1 Even patients without lung injury require baseline PEEP to prevent atelectasis.
Monitor hemodynamics closely during PEEP titration, as increased intrathoracic pressure may reduce venous return and cardiac preload. 4 This is particularly important when escalating PEEP levels above 10 cm H₂O.