Reducing supplementary oxygen given to patients in intensive care units (ICUs) does not deliver any clear and obvious health benefits or harm their chances of survival, according to new research.
Each year, about 184,000 patients are admitted to NHS ICUs, more than 30 per cent of whom need breathing support in the form of oxygen provided through mechanical ventilators.
However, there is insufficient evidence to guide the use of oxygen, with the possibility that administering too much, or too little, oxygen may not deliver the intended benefits and could end up causing patients additional harm.
That prompted researchers to establish UK-ROX, the largest ever clinical trial of oxygen use in UK ICUs, who recruited 16,500 patients from almost 100 ICUs in the UK.
They then sought to establish whether a strategy of conservative oxygen therapy – delivering less oxygen to maintain a person’s oxygen saturation at around 90 per cent – would reduce mortality rates among ICU patients.
Results published in JAMA
The results – published in the journal JAMA – showed there was no statistically significant difference in patient outcomes with 35.4 per cent of patients receiving conservative oxygen therapy having died within 90 days of their admission compared with 34.9 per cent of patients receiving usual oxygen therapy.
As a result, they believe it is safe to allow oxygen levels to be lower in ICU patients but that it may not necessarily be better for them in terms of survival, with the need to develop and evaluate more personalised therapies based on a person’s specific medical conditions.
‘[The study outcome] means that we will have to come up with ways of determining how much oxygen an individual patient needs and deliver it to them in a precise way if we are to improve patient outcomes’ [Daniel Martin]
Further clarification needed on oxygen use
The UK-ROX trial, funded by the National Institute for Health and Care Research (NIHR), was led by researchers at the University of Plymouth’s Peninsula Medical School and the Intensive Care National Audit & Research Centre.
Daniel Martin, professor of perioperative and intensive care medicine at the University of Plymouth and a consultant at University Hospitals Plymouth NHS Foundation Trust, is co-chief investigator of the UK-ROX trial.
He said: ‘Administering supplemental oxygen through mechanical ventilation is a standard course of treatment for many of those admitted to intensive care. However, there is insufficient evidence to guide us on what oxygen levels deliver the greatest benefits or have the potential to cause harm.’
Professor Martin added: ‘The results of this study show that reducing supplementary oxygen results in no overall benefit or harm to the patients, but that doesn’t mean it is not important for intensive care patients. On the contrary, it means that we will have to come up with ways of determining how much oxygen an individual patient needs and deliver it to them in a precise way if we are to improve patient outcomes.’
ICU staff and patients thanked
Paul Mouncey, co-director of the London-based Intensive Care National Audit & Research Centre and the other co-chief investigator of the UK-ROX trial, said: ‘UK-ROX is the largest individually randomised trial conducted in intensive care in the UK. The study has provided much needed robust evidence to inform clinicians in their day-to-day management of patients.’
Mr Mouncey said that a study of this size was only feasible by using routinely collected data held within NHS England and the Case Mix Programme, the national clinical audit of adult critical care in England, Wales and Northern Ireland. ‘We would like to thank the 97 NHS hospitals and 16,500 patients and their families for taking part in the clinical trial,’ he added.
Co-investigator Professor Mike Grocott, director of the NIHR Southampton Biomedical Research Centre, added: ‘This landmark study clarifies the safety of administering lower levels of oxygen to critically ill patients. Understanding how to individualise oxygen therapy will be the next step in improving patient care.’
A cost-effective study
In addition to being published in JAMA, Professor Martin and Mr Mouncey presented the results of the UK-ROX trial to delegates at the Critical Care Reviews Meeting 2025 in Belfast on 12 June.
The study and presentation also include details of how they were able to deliver UK-ROX at a fraction of the usual cost (around £100 per patient) of a randomised control trial, showing that clinical trials can be conducted differently and cost-effectively in an increasingly challenging financial climate.
The full study – titled Conservative Oxygen Therapy in Mechanically Ventilated Critically Ill Adult Patients: The UK-ROX Randomized Clinical Trial – is published in JAMA, DOI: 10.1001/jama.2025.9663.
