Technical Case Study
From: NHS Scotland
Approach:
- Nitrous oxide is a potent greenhouse gas used for anesthesia and analgesia in healthcare.
- System loss and waste of medical nitrous oxide can be successfully reduced by applying a Lean Six Sigma DMAIC methodology (Define, Measure, Analyze, Improve and Control), resulting in tangible emissions reductions from healthcare operations.
Why take action?
Globally, anaesthetic gases are responsible for ∼2-3% of Healthcare’s carbon footprint. The United Kingdom has steadfastly reduced its emissions associated with volatile hydrofluorocarbon agents through adjustments in clinical practice. By 2019/20 nitrous oxide usage remained unchanged and NHS Scotland’s emissions associated with nitrous oxide products accounted for over 88% of the total anaesthetic and analgesic gas footprint – or a total of 28,363 tonnes in carbon dioxide equivalents, comparable to 32,000 economy flights from New York to Paris.
In terms of our climate, this is a concern, as nitrous oxide is the dominant ozone-depleting substance, a potent greenhouse gas with a Global Warming Potential (GWP) 100 298 times that of carbon dioxide and persists in the atmosphere for 120 years. As such global efforts to mitigate this molecule are of high interest.
In 2020, Scottish research demonstrated that much of NHS Scotland's piped anaesthetic nitrous oxide was lost before it reached a patient. Initial test sites consistently registered high system losses in the range of 83–100% (Chakera et al)
By 2021, through establishing the Nitrous Oxide Project, the research lead successfully demonstrated across 16 hospitals that system loss and waste across the UK and ROI was driven by leakage within the piped infrastructure at manifold connections, outlet valves and junctions; theft of cylinders; poor stock management and over-provision.
A Scottish and UK-wide implementation plan was developed based on utilising Lean Six Sigma’s DMAIC framework. The Nitrous Oxide Project and mitigation activities have spanned to Australia, New Zealand, Canada, USA and South Africa and the work has received several UK and international awards.
This case study outlines the mitigation approach developed in Scotland and successfully applied globally to mitigate loss and waste of medicinal nitrous oxide within healthcare facilities.
Key messages
- The supply of nitrous oxide often exceeds clinical utility. Health facilities should ensure that the supply system aligns with demand and undertake regular review.
- The Nitrous Oxide Project is a high impact (emission mitigation) low-cost project that promotes education and training and supports existing standards for medical gas management within healthcare facilities.
- Within Scotland, monthly anaesthetic nitrous oxide emissions continue to drop and are now at 60% of the 2018/19 baseline. The removal of redundant piped systems has saved NHS Scotland around £700K due to reduction in gas turnover and infrastructure maintenance. Similarly, mitigation of analgesic nitrous oxide which in the UK is delivered in a premixed combination of nitrous oxide and oxygen is now being actioned with monthly emissions now down by 15% from its 2022/23 baseline.
How to get started
At a national or regional level, it is useful to build project momentum through a "Rapid Improvement" event (also known as "Kaizen blitz"). Such an event would include expert speakers who have successfully implemented this project and can support sites with in-person or online workshops to discuss their project with a knowledgeable mentor.
The purpose is to encourage any healthcare facility or home care provider (community midwives for example) administering nitrous oxide to establish a nitrous oxide mitigation project.
Key learning: Establish a multidisciplinary project group
Healthcare facilities that purchase nitrous oxide products must establish a multidisciplinary project group to minimise loss and waste of this agent and will be responsible for the following:
- removing redundant supply,
- reducing surplus supply,
- repairing semi-permanent and permanent junctions, and
- revising the mitigation plan quarterly, biannually or annually
Overall, a key recommendation arising from this project is that piped anaesthetic nitrous oxide systems should not be routinely introduced into new operating theatre complexes.
Key learning: Apply a Quality Improvement approach
Table 1. Implementation steps using the 5 step iterative DMAIC approach
Step | Stakeholders | Actions |
|---|---|---|
1. Define | Clinical, infrastructure pharmacy or procurement teams, clinical engineers, Quality Improvement leads and security | Identify key personnel and stakeholders Create a dedicated working group and an action plan suited for the facility |
2. Measure | Pharmacy or procurement team | Measure the total cylinder turnover |
Pharmacy or procurement and infrastructure teams | Find documentation/logbooks of cylinder bank changes. Document frequency of changes per manifold | |
Infrastructure and pharmacy or procurement teams | Review the management of manifold cylinders (safety of storage, routine leak tests, stock management) | |
Infrastructure and clinical team | Check and update piped schematics. Document number and location of outlets per manifold | |
Clinical engineering and clinical teams | Qualitative and quantitative measurement of nitrous oxide clinical usage | |
3. Analyse | Working group | Are manifold turnovers proportionate to clinical usage? How much leakage and where is it suspected? Is cylinder stock expired at manifold? Is security up to standard? Any clinical areas or manifolds that have no clinical nitrous oxide usage? |
With STEP 3. Analyse, it is useful to utilise other Quality Improvement (QI) tools such as process mapping and/or decision tree analysis.
Figure 1: Example of Decision Tree Analysis
Step | Stakeholders | Actions |
|---|---|---|
4. Improve | Infrastructure and clinical team | Terminate supply and decommission manifold (i.e. capping) where there is zero clinical usage |
Infrastructure teams and specialist medical gas engineers | Further investigation of suspected leakage | |
Pharmacy or procurement infrastructure, and clinical team | Adapt stock levels, procurement and reduce cylinder bank size to avoid stock expiring on the manifold or cap the manifold and change to a portable supply | |
5. Control | Working group with Quality Improvement (QI) specialist | Set up a continuous control and monitoring system. |
Key questions linked to actions and review in the improvement process are shown below.
Figure 2: Iterative improvement is embedded into national directives
Tracking progress
Since 2021 within the UK all NHS facilities’ emissions for nitrous oxide products are tracked centrally. Within NHS Scotland health boards are obliged to report progress of mitigation of this agent within their Annual Delivery Plans.
To assist this process the Scottish National Programme ensures that granular supplier data on the utility of various nitrous oxide products is shared monthly with regional boards’ Improvement leads so they can continue to monitor and iteratively minimise loss and waste of this agent.
A quarterly summary is also produced with tracking graphs to illustrate how different facilities are performing.
In practice
Mitigation of anaesthetic nitrous oxide is a priority within the Scottish Government and NHS Scotland Climate Emergency and Sustainability Strategy 2022–2026.
The founder of the Nitrous Oxide Project - Alifia Chakera - joined the Scottish Government in late 2021. Working with NHS Scotland, the Scottish Government has produced several reports to support the mitigation of anaesthetic nitrous oxide from a quality improvement and technical perspective.
There is a robust collaborative relationship between the programme lead and NHS Assure principal engineers, authorising engineers, medical physics estate leads and quality assurance service pharmacists. Lastly, health boards can, and do, seek advice from the programme lead.
Data is monitored and analysed at a national level and shared with boards on a quarterly basis. This allows unusual patterns of nitrous oxide turnover at NHS Scotland sites to be detected, most obviously as a spike in consumption of anaesthetic nitrous oxide either from portable or piped supply that cannot be accounted for by clinical use alone. This has allowed rapid resolution of these issues by assisting the NHS site directly.
Challenges at a board level are linked to a dearth of specialist staff, especially those able to authorise changes to medical gas supply. Additionally, hospitals with privately financed facility arrangements can often face delays in decommissioning redundant nitrous oxide supplies until contractual arrangements are resolved.
The founder of the Nitrous Oxide Project and programme lead for Scotland has supported mitigation programmes across the UK collaborating with the Greener NHS Programme, the Welsh Government and Northern Ireland.
Key resources
- More information can be found in the Nitrous Oxide Project poster.
- The Nitrous Oxide Project | Centre for Sustainable Healthcare (video)
Technical Briefs
- NHS Scotland Nitrous Oxide Mitigation Implementation Plan
- Technical update: Anaesthetic nitrous oxide system loss mitigation and management
- Greenhouse gas mitigation – Entonox – technical briefing
- NHS Scotland climate emergency and sustainability strategy: 2022-2026
References
- Chakera A, Fuhrmann A. Hospital action plan for mitigating anaesthetic nitrous oxide emissions. Br J Anaesth [Internet]. 2024;133(6):1514–7. Available from: http://dx.doi.org/10.1016/j.bja.2024.08.021
- Southall P, Shelton C, Chakera A. Consensus on decommissioning piped nitrous oxide from UK and Ireland operating theatre suites: a rational approach to an increasingly ignoble gas. Anaesthesia [Internet]. 2024;79(12):1274–9. Available from: http://dx.doi.org/10.1111/anae.16407
- Chakera A, Harrison S, Mitchell J, Oliver C, Ralph M, Shelton C. The Nitrous Oxide Project: assessment of advocacy and national directives to deliver mitigation of anaesthetic nitrous oxide. Anaesthesia [Internet]. 2024;79(3):270–7. Available from: http://dx.doi.org/10.1111/anae.16211
- Chakera A, Pearson F. Nitrous oxide mitigation, look before you leap. Anaesthesia [Internet]. 2022;77(12):1454. Available from: http://dx.doi.org/10.1111/anae.15862
- Conference Abstracts (2021) 011, 021, 029, 039, 056, Abstracts of the Annual Congress 2021 23‐24 September 2021, virtual conference. Anaesthesia [Internet]. Accessible from: https://associationofanaesthetists-publications.onlinelibrary.wiley.com/doi/10.1111/anae.15578
- Chakera A. Dissertation. Masters in Public Health Dissertation University of Edinburgh July 2020 Reducing the impact of nitrous oxide emissions within NHS Lothian theatres to mitigate dangerous climate change. 2020. Accessible from: https://osf.io/z7h3a/