UMEM Educational Pearls

Title: How low can the O2 go? Choosing a SaO2 goal in the mechanically ventilated patient

Keywords: Critical Care, oxygen, ventilator, SaO2 (PubMed Search)

Posted: 9/2/2025 by Zachary Wynne, MD
Click here to contact Zachary Wynne, MD

What is the ideal oxygen saturation goal for a mechanically ventilated patient? Literature over the past decade has led away from the perfect 100% oxygen saturation due to its association with worse patient outcomes across many disease states. It is theorized that excess oxygen leads to free radical production causing a lung injury pattern. However, there is no clear guidance for the ideal range of oxygen saturation goals, particularly in the mechanically ventilated patient, despite a meta-analysis and several recent trials.

UK-ROX Trial - JAMA - June 2025

Question: Does an oxygen saturation goal of 88-92% lead to a lower 90-day mortality compared to usual care?

Population: 16,500 mechanically ventilated adult patients in 97 ICU’s across the UK, excluded patients on ECMO

Intervention: Goal oxygen saturation of 88-92%, using the lowest possible FiO2

Control: Usual care, defined as oxygen supplementation at the discretion of the treating physician (no limits set to FiO2 or SaO2)

Outcomes:

Conservative and usual therapy groups were randomized 1:1 and had similar characteristics
90 day all-cause mortality - 35.4% in conservative group vs. 34.9% in usual care group (p=0.28)
Time at 88-92% SaO2 - 62.6 hrs in conservative group vs. 27.2 hrs in usual care group (did not look at oxygen exposure peri-intubation)
No difference in secondary outcomes - duration of ICU stay, days alive and free of organ support, duration of acute hospital stay, and others

Bottom Line:

Ideal oxygenation targets remain elusive. UK-ROX adds to the growing literature of oxygenation targets in mechanically ventilated patients but does not clearly show that lower oxygen saturation targets lead to improved ICU outcomes. In your emergency department ICU boarder, avoid a 100% oxygen saturation to prevent oxygen toxicity associated lung injury and consider an oxygen saturation goal of 90-96% (88-92% if history of COPD).

References

Martin DS, Gould DW, Shahid T, Doidge JC, Cowden A, Sadique Z, Camsooksai J, Charles WN, Davey M, Francis-Johnson A, Garrett RM, Grocott MPW, Jones J, Lampro L, Mackle DM, O'Driscoll BR, Richards-Belle A, Rostron AJ, Szakmány T, Warren A, Young PJ, Rowan KM, Harrison DA, Mouncey PR; UK-ROX Investigators. Conservative Oxygen Therapy in Mechanically Ventilated Critically Ill Adult Patients: The UK-ROX Randomized Clinical Trial. JAMA. 2025 Aug 5;334(5):398-408. doi: 10.1001/jama.2025.9663. PMID: 40501321; PMCID: PMC12163715.