PEEP Settings and Titration in Mechanical Ventilation

ARDS Patients – Severity‑Based PEEP Recommendations

Higher PEEP (≈15 cm H₂O) versus lower PEEP (≈9 cm H₂O) reduces 28‑day mortality in moderate‑to‑severe ARDS (PaO₂/FiO₂ < 200) (adjusted RR 0.90; 95 % CI 0.81‑1.00) based on an individual‑patient‑data meta‑analysis of three large randomized trials (high‑quality evidence). 1
Higher PEEP raises the PaO₂/FiO₂ ratio by ~61 mm Hg without increasing barotrauma or new organ‑failure events (physiologic benefit). 1
In mild ARDS (PaO₂/FiO₂ > 200), higher PEEP provides no mortality benefit and may be harmful (adjusted RR 1.29). 1
Physiologic rationale: higher PEEP reduces atelectasis, increases end‑expiratory lung volume, and prevents cyclic recruitment‑derecruitment injury at the interface of collapsed and aerated lung tissue.** 1
PEEP also counteracts the added lung weight from interstitial and alveolar edema that characterises ARDS. 1

Apply PEEP of 6‑10 cm H₂O together with low tidal volume ventilation (6‑8 mL kg⁻¹ predicted body weight) to lower postoperative pulmonary complications, improve respiratory system compliance, increase end‑expiratory lung volume, and enhance dependent‑lung ventilation. [2][3]
Zero end‑expiratory pressure (ZEEP) must be avoided; it causes immediate loss of end‑expiratory lung volume, atelectasis formation, reduced compliance, and heightened risk of volutrauma in aerated regions. [2][3]
Maintain PEEP during emergence from anesthesia and avoid a period of apnea with ZEEP before extubation; optimise patient positioning to support lung mechanics. 2
Continuous intra‑operative monitoring should include oxygenation, plateau pressure (<30 cm H₂O), driving pressure, and haemodynamics; recognise that intra‑operative improvements may diminish after extubation, so ventilatory mechanics should be optimised throughout the case. [1][2]

Consider recruitment maneuvers (e.g., sustained CPAP 30‑40 cm H₂O or incremental PEEP steps) in conjunction with higher PEEP; they increase PaO₂/FiO₂ by ~52 mm Hg at 24 h and reduce the need for rescue therapy (RR 0.64). 1
Recruitment maneuvers carry a risk of haemodynamic compromise and barotrauma; close monitoring is mandatory during their application. 1
Overall ventilatory monitoring should continuously assess oxygenation, keep plateau pressures below 30 cm H₂O, track driving pressure, and evaluate haemodynamic stability to balance recruitment benefits against over‑distension risk. 1