Conservative versus liberal oxygen therapy for mechanically ventilated patients: a systematic review and meta-analysis of randomized controlled trials

Background Currently, clinicians lack sufficient evidence to determine which oxygen therapy approach yields better outcomes in mechanically ventilated (MV) patients, whether conservative oxygen therapy (COT) or liberal oxygen therapy (LOT). Methods This study systematically searched for randomized controlled trials (RCTs) in PubMed, Embase, Web of Science, and Cochrane Library from the inception of each database to 1 September 2025. The outcome measures in MV patients included overall mortality, intensive care unit (ICU) mortality, 90-day mortality, ICU length of stay (LOS), hospital LOS, and MV hours. Results This meta-analysis included 11 RCTs published between 2014 and 2025, involving a total of 20,786 adult MV patients. There was no significant difference in overall mortality between the COT and LOT groups (RR 1.02, 95% CI 0.95–1.10; Z = 0.54, p = 0.59) nor in ICU mortality (RR 1.07, 95% CI 0.89–1.33; Z = 0.71, p = 0.48) and 90-day mortality (RR 1.04, 95% CI 0.96–1.12; Z = 0.92, p = 0.36). There was no significant difference in ICU LOS between COT and LOT (MD −0.02, 95% CI −0.05–0.01, Z = −1.42, p = 0.15), or in hospital LOS (MD 0.00, 95% CI −0.06–0.07, Z = 0.14, p = 0.89), and MV hours (MD −0.05, 95% CI −0.92–0.81, Z = −0.12, p = 0.91). Conclusion In this meta-analysis of MV patients, COT was not associated with a reduction in overall mortality, ICU mortality, 90-day mortality, ICU LOS, hospital LOS, and MV hours when compared with LOT. The absence of overall benefit from COT in this broad population does not preclude the possibility that selected subgroups or different target ranges could prove advantageous. Systematic review registration https://www.crd.york.ac.uk/PROSPERO/view/CRD420251137389 .