Nitrous Oxide “Cracking” Can Reduce Greenhouse Gas From Pain Killer Used During Childbirth What is meant by ‘cracking’ nitrous oxide?

Response: A molecule of nitrous oxide is composed of two nitrogen atoms and one oxygen atom. Using a heated catalyst, it can be broken down, or ‘cracked’, into nitrogen and oxygen gas; the major components of air. This prevents the release of environmentally harmful nitrous oxide into the atmosphere. What should readers take away from your report?

Response: Nitrous oxide contributes to the climate crisis and has occupational exposure implications for healthcare workers. However, its use as a painkiller in labour is embedded within many maternity services. The introduction of cracking technology can reduce the environmental and occupational impacts of nitrous oxide in the maternity setting, but because it relies on the patient consistently breathing out into a facemask or mouthpiece to capture the exhaled gas, the process depends on good communication and cooperation. We are keen to emphasise that even when cracking is used, nitrous oxide is still likely to have a higher ‘carbon footprint’ than alternative techniques. What recommendations do you have for future research as a result of this study?

Response: Ambient levels are not a direct measure of the proportion of nitrous oxide cracked – this would require measuring the mass of nitrous oxide used, and the mass broken down. Future research could more precisely calculate the ‘carbon footprint’ impacts of introducing cracking technology, it may also help to further define the optimal approach to implementation, as well as when and how to educate patients and healthcare workers on the technology. Is there anything else you would like to add? Any disclosures?

Response: Nitrous oxide is used for other purposes as well as of pain relief in labour. Whilst its use is likely to continue in maternity in the UK – because of tradition, logistics and patient preferences – alternatives such as intravenous painkillers are more straightforward to implement in other settings such as operating theatres, and clinicians should seek reduce its use when viable alternatives exist. Furthermore, there is increasing evidence that most of the nitrous oxide supplied to hospitals is wasted. Efforts to reduce waste and decommission unnecessary nitrous oxide cylinder manifolds should be prioritised above other measures.

Any disclosures?

Medclair Invest, BPR Medical and Intersurgical provided the equipment used in the study free of charge on a trial basis. These companies had no input into the project design. The authors thank the Manchester University NHS Foundation Trust Sustainability Team for supplying the N2O monitor for the project. No external funding and no other conflicts of interest declared


Pinder A, Fang L, Fieldhouse A, Goddard A, Lovett R, Khan-Perez J, Maclennan K, Mason E, MacCarrick T, Shelton C. Implementing nitrous oxide cracking technology in the labour ward to reduce occupational exposure and environmental emissions: a quality improvement study. Anaesthesia. 2022 Sep 15. doi: 10.1111/anae.15838. Epub ahead of print. PMID: 36108342.

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Last Updated on September 20, 2022 by