From pipes to cylinders: reducing nitrous oxide at the Horton

More than 500 tonnes of carbon dioxide equivalent (CO₂e) will be saved every year at the Horton General Hospital, following the decommissioning of its nitrous oxide (N₂O) manifold.

Since February 2024, the Banbury hospital has used a portable supply of N₂O in small cylinders, which are wheeled into theatres when required, helping Oxford University Hospitals NHS Foundation Trust (OUH) reduce its carbon footprint.

Despite being part of healthcare delivery, N₂O is a harmful greenhouse gas.

The gas, occasionally used by anaesthetists for sedation and pain relief among other things, was previously distributed via a manifold, a system that delivers N₂O to the pipelines around the hospital. Audits across UK hospitals have found this to be wasteful.

Instead, it is now delivered to patients on an individual basis and, as a result, much smaller amounts of the gas are kept on site.

An OUH-wide audit suggested that the Horton was only using approximately 5% of the N₂O ordered (618 tonnes CO₂e) and that 95% of this (587 tonnes CO₂e) can be saved. The 587 tonnes CO₂e saving is estimated to be the equivalent of approximately:

• 261,586 return train journeys between Banbury and Oxford per year
• 345 tonnes of plastic (1kg plastic = 1.7kg CO₂e)
• Leaving a low-energy light bulb on for 39,133 years.

It is also expected to save approximately £8,000 annually from 2025 onwards.

Speaking on the Sustainability Day of Action (Monday 8 July), Dr Marta Astraverkhava, a Consultant Anaesthetist at OUH, said: "We as a team were determined to identify nitrous oxide wastage so we could reduce its environmental impact and support the Trust- and NHS-wide pledge to be net zero by 2040.

"We are proud to be able to change our approach at the Horton and vastly reduce the amount of nitrous oxide being wasted."

Using nitrous oxide cylinders that attach directly to the anaesthetic machines instead of via long pipes improves efficiency and removes risks of leaks.

The Horton accounted for about half of the pure nitrous oxide footprint across the four OUH hospitals and is the first to switch off the wall supply and move to a portable supply of the gas. The Nuffield Orthopaedic Centre, Churchill Hospital and John Radcliffe Hospital, all located in Oxford, are preparing to make the switch in due course.

Mark Holloway, Chief Estates and Facilities Officer with responsibility for sustainability at OUH, said: "Exploring the disposal of nitrous oxide across the Trust was an action included in the OUH Green Plan, so we are pleased to make such a big step forward in our efforts to reduce the Trust’s carbon footprint in this way.

"While we still have work to do to reduce nitrous oxide across the wider organisation, I am thankful to my colleagues whose hard work and dedication to delivering sustainable improvement has delivered this important project."

Stuart Kinton, Chair of the OUH Sustainability Network, said: "The OUH Sustainability Network would like to congratulate and celebrate the multidisciplinary team who identified the need for this project and who have invested a lot of time and effort in making it a reality alongside their regular duties.   

"This project will help OUH on its journey towards the national target for a net zero NHS carbon footprint by 2040. Achieving this goal will take significant ambition and engagement across all areas of the Trust; and is a project is a great example of that level of ambition and the impact that this type of work can have on the Trust’s carbon footprint."

Pictured: From left - Aaron Fleming (Anaesthetic Registrar), James Boyd-Horton (Horton ODP), Karen Wentworth-Foster (Horton Theatre Manager), Marta Astraverkhava (Anaesthetic Consultant)