Sustainable healthcare case study: Reduction in nitrous oxide waste by Southern Cross Healthcare

Thursday 30 March 2023

Southern Cross Healthcare (SCH) group is New Zealand's largest non-public health care organisation. Its network includes ten wholly owned and five joint venture hospitals. As a GGHH Pacific member, SCH is working to investigate and implement strategies to reduce use of high carbon emission anaesthetic gases such as nitrous oxide gas use in anaesthesia as part of their National Sustainability Plan 2021-2025.

The problem

In the UK, total emissions for anaesthetic gases represent 2% of the NHS footprint, which more than half of which comes from nitrous oxide (N2O). Furthermore, N2O is a major cause of ongoing ozone depletion, which is not captured by the Montreal Protocol. 


  • Reduce use of high carbon emission anaesthetic gases such as nitrous oxide

The process

The impact of nitrous oxide usage during routine anaesthetic machine check was investigated at Southern Cross Christchurch Hospital. The default flow rate was 6 L/minute. The investigation found 2 L/minute flow rate is the optimal flow in terms of balancing the time taken to complete the check and has a 43% reduction in nitrous oxide usage. This result was shared among the anaesthetic technicians working in the hospital, to advocate to reduce the flow to 2 L/minutes when checking the nitrous oxide content.

This strategy was implemented by the charge anaesthetic technician, a staff meeting was held to announce the change of practice and rationale for this change. The hospital machine check guideline specified to use 2L/minute when checking nitrous Oxide and the machine check booklet was reprinted for each machine, which served as a reminder for staff. All anaesthetic technician staff were very receptive of the change, and it didn’t require any extra training, no change was made to the anaesthetic machine, and only the anaesthetic technicians were involved in the change.

The outcome

  • Estimated reduction of 1166 L of nitrous oxide per year, equivalent to 687 kg of carbon dioxide (or driving 2784 km by a patrol car)
  • Financial benefits through saving on nitrous oxide

The next steps

There are several opportunities to expand the project:

  • Collecting longterm data to understand how this change of practice is collectively having on conserving nitrous oxide gas
  • Changing the default machine flow setting to 2 L/min to remove the manual requirement to lower the flows during machine check
  • Implement this process change across the Southern Cross Network of hospitals
  • Change machine check policy and guideline at the national level
  • Ongoing education and awareness integrated in training for all anaesthetic technicians and appropriate clinical teams

This full case study is available to GGHH members via GGHH Connect.

Congratulations Southern Cross Healthcare! Thank you for your sustainable healthcare leadership!