Each year, around 184,000 patients are admitted to NHS intensive care units (ICUs) and over 30% need breathing support. Ventilators (breathing machines) provide oxygen to these patients, helping them to recover.

The optimal amount of oxygen a patient needs is currently unknown. Both too much, and too little, oxygen may cause harm. The concentration of oxygen given through the ventilator is adjusted according to how much oxygen can be detected in a patient’s blood, known as oxygen saturation. Some studies suggest that having lower, rather than higher, oxygen saturation may be better for seriously ill patients in hospital.


UK-ROX is a large-scale clinical trial trying to find out if using a lower oxygen saturation target (conservative oxygen therapy) to guide oxygen treatment might lead to better outcomes for patients when compared with the approach currently used in NHS ICUs (usual oxygen therapy).

The study will include 16,500 patients from around 100 UK ICUs. Patients will be randomly assigned to either the conservative or usual oxygen therapy group. We will follow all patients involved in the study for up to 90 days by ‘linking’ study data with routinely collected national records.

Results from this study will have a large and immediate impact on ICU clinical practice and on patient outcomes throughout the NHS.

You can follow us on X (formerly Twitter) @UKRoxTrial for updates on the study.

Key information

Chief investigator(s)

Professor Daniel Martin OBE, University of Plymouth

Mr Paul Mouncey, ICNARC


Intensive Care National Audit & Research Centre (ICNARC)


National Institute for Health Research (NIHR) – Health Technology Assessment (HTA) Programme

(Project Number: NIHR130508)

Trial registration(s)

ISRCTN Registry: ISRCTN13384956

NIHR Central Portfolio Management System: 46926

Contact information

Trial Manager – Tasnin Shahid


Phone: 020 4513 6238

Trial protocol
Statistical analysis plan