Dr Ronan O'Driscoll, ProfNawar Bakerly

Oxygen: No need for too much of a good thing

New research suggests that it is safe for hospitals to use less oxygen when treating patients. The study, based on more than half a million bedside observations of patients at Salford Royal Hospital, part of the Northern Care Alliance NHS Foundation Trust in Greater Manchester, suggests that other UK hospitals can safely reduce the amount of oxygen which is given to patients. There may also be safety benefits for patients.

Oxygen therapy has been common in hospital settings for more than 100 years and each day, around one in seven patients in UK hospitals is receiving oxygen. International guidelines differ on what the standard oxygen saturation target range as measured by an oxygen device (pulse oximeter) should be, prompting this study which is published in the journal BMJ Open Respiratory Research. Most UK hospitals follow the guidance of the British Thoracic Society  which was first published in  2008. This guideline recommends aiming for a target oxygen saturation range of 94-98% for most patients. This means that oxygen is not required if a patient’s oxygen saturation breathing air is at or above 94%. Furthermore, the concentration or flow of oxygen should be lowered if a patient is on oxygen and the saturation rises above 98%.

A lower target oxygen saturation range of 92-96% would bring the UK into line with recommended practice in Australia, New Zealand and Germany. It would also reflect NHS practice during the Covid 19 pandemic when the recommended oxygen saturation target levels were reduced to 92-96% to preserve supplies.

Routine observations

The new recommendation is based on data from observations on patients at Salford Royal Hospital in 2019 and 2022.  The study compared anonymised records from 2019 when the target range was 94-98%, with data from 2022 when the target range was 92-96%. Most of the data arose from routine observations on medical, elderly care and surgical wards.

The research showed that fewer patients had hyperoxaemia (too much oxygen) with the lower target oxygen saturation range of 92-96% in 2022 compared with 2019 when the standard target oxygen saturation range of 94-98% was in use. There was a reduction of 1.5% in the risk of hyperoxaemia in 2022 (3.9%) compared with 2019 (5.4%). Previous research has found that hyperoxaemia is associated with an increased risk of death.

Despite concerns that a lower target range could lead to more patients being exposed to hypoxaemia (opposite to hyperoxaemia when oxygen saturation falls below 90%), the proportion of observations showing hypoxaemia in 2022 was only 0.20% which was very close to the 2019 proportion of 0.16%.

This means that aiming for a lower oxygen target saturation range of 92-96% led to a reduction in the risk of hyperoxaemia of one for every 68 observations, compared to a much smaller increase in the risk of hypoxaemia of one for every 2500 observations.

Real world data

This study is the first of its kind using real world data to evaluate the safety of a lower oxygen target saturation range in such a large number of patients across multiple specialisms.

The research was led by Respiratory Consultant Dr Ronan O’Driscoll and colleagues at Salford Royal Hospital in collaboration with experts from The Medical Research Institute of New Zealand.

Dr O’Driscoll said: “Both too little oxygen (hypoxaemia) and too much (hyperoxaemia) are dangerous for patients so it is crucial that oxygen is prescribed and documented in hospital like any other medication. We set a personalised target range for each patient that is a safe level of oxygen in the blood that hospital staff can measure and keep within. Our study establishes that a lower target oxygen saturation range is safe and lowers the risk of over-oxygenation which can be a particular problem for those with lung diseases.”

Dr O’Driscoll led the production of the British Thoracic Society Guideline for oxygen use in hospitals in 2008. This guideline (updated in 2017) was the first national guideline related to the use of oxygen in hospitals.

Co-author Professor Nawar Bakerly, who is also a Respiratory Consultant at Salford Royal Hospital, added: “Our findings are a major contribution to the evidence base supporting a lower target range of oxygen saturation for most patients.”

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