Media release

From: Association of Anaesthetists

Study shows potential for ‘cracking’ technology to reduce environmental impact of nitrous oxide used during labour

A study published in Anaesthesia (a journal of the Association of Anaesthetists) shows the potential for using ‘cracking’ technology to reduce the environmental impact of nitrous oxide (N2O), used extensively to manage pain during labour.

The study was conducted by a multidisciplinary team of anaesthetists and midwives, from St John’s Hospital, Livingston, UK and Manchester University NHS Foundation Trust, Manchester, UK. The lead author of the study is Dr Annie Pinder, Fellow in Sustainable Healthcare at the North West School of Anaesthesia, Manchester, UK. The study was supervised by Consultant Anaesthetist Dr Cliff Shelton, of Wythenshawe Hospital and Lancaster University, UK.

All inhaled anaesthetic gases in common use today are greenhouse gases. Compared to an equivalent mass of carbon dioxide (CO2), nitrous oxide has 265 times the global warming potential. Nitrous oxide, the painkilling component of ‘gas and air’, is the most frequently used labour painkiller in the UK, and is available in all birth settings. Thus, any intervention that reduces nitrous oxide release into the atmosphere has the potential to significantly reduce the environmental impact of this medication.

One method which may reduce the carbon footprint of nitrous oxide is to break down (‘crack’) the exhaled gas into nitrogen and oxygen using a catalyst. Previous research has established the efficiency of this process – however, to be effective in practice, as much exhaled nitrous oxide as possible must be ‘scavenged’ (captured) so that it can be broken down. This relies on patients being able to consistently breathe out into a mask or mouthpiece.

In this quality improvement project, based on environmental monitoring and staff feedback, the authors assessed the impact of nitrous oxide cracking technology in the maternity setting. Nitrous oxide levels were recorded during the final 30 minutes of uncomplicated labour in 36 cases. In the first 12 cases, readings were taken without the use of the technology to establish a baseline. Subsequently, the study team introduced the cracking device, and took a stepwise approach to optimising its clinical use. This involved using a mouthpiece, then two different types of facemask, and providing patients with tips for use and feedback.

The results showed that median ambient nitrous oxide levels were 71% lower than baseline when using a mouthpiece, and 81% lower when using a low-profile facemask (a lightweight facemask with a flexible seal) together with coaching on how best to use it. The authors say: “Given that a similar magnitude of reduction in nitrous oxide levels was seen with mouthpieces and low-profile facemasks, we suggest that pregnant women should be offered the option of either device when cracking is used. Education for pregnant women and choice in use of device is vital given the high degree of co-operation required [for the successful use of the technology], and this is consistent with guidelines for choice and personalised care in maternity services. Future research to better characterise the optimal use of this technology could focus on investigating other delivery device types, and considering the optimal timing and method of education – for example, is the antenatal clinic a better place to discuss this technology than during the birth period?”

The authors note that they attempted to avoid burdening pregnant women with ‘climate guilt’ during their labour; for example by making it clear that greenhouse gas emissions associated with nitrous oxide are the responsibility of the healthcare organisation – rather than of the patients.

They add: “Staff feedback was generally positive, though some found the technology to be cumbersome; successful implementation relies on effective staff engagement. Our results indicate that cracking technology can reduce ambient nitrous oxide levels in the obstetric setting, with potential for reductions in environmental impacts and occupational exposure.”

Anaesthetist who used nitrous oxide ‘cracking’ system while herself giving birth says technology is mostly easy to use, and describes positive feelings of reducing environmental impact

Embargo 2301H UK time Thursday 15 September

In a case report published in Anaesthesia Reports (a journal of the Association of Anaesthetists), a 35-year-old woman who is herself an anaesthetist describes her own use of special equipment to recover and break down nitrous oxide used for pain relief during her labour, saying it is mostly easy to use and also discussing the positive feeling of reducing harm to the environment.

As discussed in another press release that accompanies this one, nitrous oxide is a greenhouse gas that has global warming potential some 265 times higher than the equivalent mass of carbon dioxide. Nitrous oxide is the most common painkiller used during labour, and thus any intervention that reduces its release has the potential to substantially reduce its impact on the environment.

Consultant Anaesthetist Dr Fiona Martin of Salford Royal Hospital, Salford, UK, used a nitrous oxide cracking device whilst in labour, prior to giving birth to a healthy baby girl at St Mary’s Hospital, Wythenshawe, part of Manchester University NHS Foundation Trust, in October 2021. The device helped to collect (‘scavenge’) and break down nitrous oxide that she breathed out via a facemask, to prevent it being released into the atmosphere.

Dr Martin says: “As a profession, we are all aware of the importance of reducing the environmental impacts of anaesthetic agents. Although I admit this was not at the forefront of my mind on the day in question, I was pleased to think that by using the cracking equipment I might help to reduce greenhouse gas emissions associated with nitrous oxide use in labour.”

During her labour she used a birthing pool, and noted that the most difficult moments to maintain a tight facemask seal (thereby maximising the amount of nitrous oxide scavenged) came when exiting the pool and changing positions during her labour – lying on her side made it more difficult, but when lying in the hands and knees in the ‘prone’ position, common during labour, It became easier as the weight of her head pressing down on the mask made the seal better. She adds: “Overall, I found the experience of using the cracking equipment to be very positive, and I am pleased to note the drop in ambient nitrous oxide once I made the switch from the usual device that provides the gas during labour.”

The case report notes that although the ambient nitrous oxide levels were low, it remained detectable throughout labour, despite Dr Martin’s expertise in facemask use as a result of her professional training. The authors say: “Increases in nitrous oxide concentrations appeared to be associated with events that were uncomfortable or presented a challenge to maintaining an effective facemask seal, such as during examinations. This suggests that the impact of cracking technology is dependent not only on the efficacy of the technology itself, but on finding ways to help patients to use it effectively. This may, for example, involve education on facemask use at antenatal classes, feedback and support from midwives during labour, or considering whether a facemask is the most suitable device for every patient in every context.”

The authors conclude: “We believe this to be the first case report of the patient’s perspective of using nitrous oxide cracking technology in labour. Based on the experiences reported above, the equipment appears to be patient-friendly and unobtrusive. It has great potential to reduce the negative environmental and occupational health impacts of nitrous oxide, but as this report indicates it does not mitigate them completely. Cracking may be part of the solution to reducing nitrous oxide emissions, but it is not the whole solution. Complementary efforts to reduce the supply and clinical use of nitrous oxide must continue if we are to approach `net zero´ healthcare.”