Out of gas!

  • 4th April 2024

How making improvements to medical gas supplies can help hospitals to reduce their carbon footprint

Dr Tom Dolphin, a consultant anaesthetist at Imperial College Healthcare NHS Trust, led the project to decommission the nitrous oxide manifold at Charing Cross Hospital

Charing Cross Hospital is one of only a handful of major hospitals in England to decommission its entire nitrous oxide manifold in one go – reducing carbon emissions by more than 460 tonnes a year.

Nitrous oxide has been used for over 175 years as part of anaesthesia within healthcare, but it is a potent greenhouse gas, estimated to be nearly 300 times worse than carbon dioxide for the environment.

And recent research revealed a significant proportion of emissions at older NHS hospitals like Charing Cross is due to waste from manifolds and the associated old pipe structure.

Speaking to Healthcare Property, Dr Tom Dolphin, a consultant anaesthetist at Imperial College Healthcare NHS Trust, which runs Charing Cross, explains: “Nitrous oxide is a key contributor to trusts’ carbon footprints.

“But, when we compared the number of empty cylinders with clinical use from our digitised anaesthetics records, we realised that the number of cases every month where it was being used clinically, and how many litres that represented, was far lower than the amount of gas we were piping through the system.

Old pipework

“We did various checks and confirmed our suspicions that almost all of our usage was in fact leaks at various points along the ageing pipework system.

“While the leaks did not pose a health risk, they were bad for the environment.”

Working with a medical gas specialist, the trust had three options: Stop providing nitrous oxide altogether and turn off the supply; attempt to repair the whole nitrous oxide pipework system; or decommission the manifold and replace it with a new supply system located much nearer to the few areas where it is still used.

Dolphin said: “There is still a need to provide nitrous oxide for the very-few clinical situations where it is used, and repairing and replacing pipework right across the building – across 14 storeys of a 50 to 60-year-building – would be a major undertaking.

“Instead, we chose the third option.

“This meant manually turning a lever to cut the flow from the cylinders, sending them back to the British Oxygen Company, and then capping off the outlets at the point of use with end blanking plates to make it clear they are no longer in use.”

Nitrous oxide is a key contributor to NHS trusts’ carbon emissions

Getting buy-in

However, getting buy-in from the various departments was a much-longer process.

“What I underestimated was the sheer number of people involved in a decision like this,” said Dolphin.

“The majority of the work was governance. We had to involve the medical gases committee, pharmacy, portering, estates and facilities, anaesthetists – a lot of people were involved, and we needed to get buy in from them all and understand their concerns.

“While the physical work is relatively minimal, what really took time was making sure we spoke to all the right people.”

But, having now completed the work, the results are already being realised.

It is estimated the move will reduce greenhouse gas emissions by at least 460 tonnes of C02e (carbon dioxide equivalent) a year – around 1% of the trust’s overall carbon footprint.

This saving is estimated to be the equivalent of driving a petrol car around the earth 57 times.  


Dr Bob Klaber, director of strategy, research, and innovation at Imperial College Healthcare NHS Trust, said: “This is a really-innovative and impactful project and I am grateful to the many teams who worked so hard over the past six months to make it possible.
“We are one of the biggest NHS trusts in the country, with an ageing estate, and are absolutely committed to reducing our impact on the environment and reaching carbon net zero before 2045.”

The trust is now looking more widely at its use of anaesthetic gases to identify additional areas for improvement.

The includes the trialling of volatile capture technology (VCT) canisters designed to capture anaesthetic gases at Charing Cross, Hammersmith, and St Mary’s hospitals, as part of a large-scale feasibility trial funded by Imperial Health Charity to reduce carbon emissions in surgery.

The canisters are designed to capture significant volumes of the exhaled anaesthetic gases, which can then be purified and reused.

And the team will use the findings from the trial to make a case to roll this out permanently across the trust.

Dolphin said: “There are currently around 90 anaesthetic machines across our hospitals, with thousands of anaesthetics given each year to patients, so making this change would be a significant step in reducing our carbon footprint.”


Aneurin Bevan Health Board has also decommissioned its system. Pictured, Dr Jenna Stevens

Welsh trust makes its mark

Decommissioning of the nitrous oxide piping system and manifold has also taken place at hospitals in Gwent as part of carbon-cutting efforts by Aneurin Bevan University Health Board.

A project carried out by the clinical workstream of the health board’s Decarbonisation Programme Board found there was significant wastage secondary to small leaks in the ageing pipelines and out-of-date gas cylinders.

Dr Jenna Stevens, a consultant anaesthetist, sustainability lead, and clinical lead for the decarbonisation board, said: “The clinical use of nitrous oxide over the last 10-15 years has dramatically reduced.

“What we were finding was that even though our use had declined, we were still purchasing a significant quantity of nitrous oxide.”

As part of the project, the team has been able to decommission systems at Ysbyty Ystrad Fawr, Nevill Hall Hospital, St Woolos Hospital and Royal Gwent Hospital.

Smaller, more mobile cylinders are now in place at all of these sites, providing the gas where necessary and reducing emissions and waste.

Financially, this represents a saving of £14,500 per year. But its environmental impact is much greater, estimated at 900 tonnes of carbon dioxide equivalent and equating to over 2.2 million miles driven by a car.

The team now plans to look at ways to reduce the impact of Entonox wastage.

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