Meta-analysis of 8 RCTs shows higher fixed PEEP increases hypotension risk in thoracic surgery patients

BackgroundHigher fixed positive end-expiratory pressure (PEEP) during one-lung ventilation (OLV) may improve intraoperative oxygenation but could compromise haemodynamic stability. We performed a systematic review and meta-analysis to evaluate the effects of higher vs. lower fixed PEEP strategies on intraoperative hypotension and postoperative pulmonary complications (PPCs) in patients undergoing thoracic surgery.MethodsWe searched MEDLINE, Embase, and CENTRAL from inception to 7 March 2026, supplemented by trial registries. Parallel-group randomised controlled trials (RCTs) comparing higher vs. lower fixed PEEP during OLV were eligible. Co-primary outcomes were intraoperative hypotension and PPCs. Pooled risk ratios (RRs) and mean differences (MDs) were estimated using random-effects models with restricted maximum likelihood (REML) estimation. Certainty of evidence was assessed using GRADE. This review was registered in PROSPERO (CRD420261329237).ResultsEight RCTs (2,747 patients) were included. Higher PEEP was associated with a significantly increased risk of intraoperative hypotension (2 studies; n = 2,086; RR: 2.16, 95% CI: 1.29–3.63; p = 0.003; I2 = 61%; moderate certainty). Higher PEEP did not significantly reduce the risk of PPCs (2 studies; n = 2,227; RR: 0.95, 95% CI: 0.88–1.02; p = 0.179; I2 = 0%; moderate certainty). New-onset arrhythmia was more frequent with higher PEEP (RR: 2.56, 95% CI: 1.76–3.71), while rescue hypoxaemia interventions were less frequent (RR: 0.37, 95% CI: 0.25–0.56). Pooled vasopressor use did not differ significantly between groups (RR: 1.05, 95% CI: 0.97–1.13). Intraoperative PaO2 was directionally higher with higher PEEP but the estimate was statistically inconclusive owing to substantial heterogeneity (I2 = 94.2%).ConclusionsHigher fixed PEEP during OLV significantly increases intraoperative hypotension risk without reducing PPCs. The haemodynamic cost of this strategy is not offset by measurable clinical benefit. Routine application of higher fixed PEEP during OLV should be approached with caution, and future research should evaluate individualised PEEP titration strategies.Systematic Review Registrationhttps://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD420261329237, identifier CRD420261329237.