This randomised controlled trial is investigating the feasibility and safety of high flow humidified nasal oxygen (HFNO) in labouring women using remifentanil for patient controlled analgesia (PCA). Opioid PCA is commonly used as pain relief for women who have contraindications to epidural analgesia such as thrombocytopaenia or who desire a non-invasive form of labour pain relief such as women undergoing vaginal birth for fetal death in utero. In our hospital, we use the opioid fentanyl, however evidence suggests that remifentanil, provides superior pain relief.
The major side effect of remifentanil PCA is maternal hypoxaemia from opioid-induced ventilatory impairment. HFNO can provide accurately titratable inspired fraction of oxygen, dynamic continuous positive airway pressure and apnoeic oxygenation. This trial is a first step towards investigating whether the addition of HFNO to remifentanil PCA is a safer option for this therapy and determine feasibility of a larger trial. If HFNO can reduce oxygen desaturation in pregnant women receiving remifentanil PCA, this could have significant application for obstetric centres worldwide, affect a shift in clinical practice and raise awareness regarding the needs of the vulnerable subpopulation of labouring women giving birth to stillborn babies.
This trial forms a component of Dr Tan’s PhD at the University of Melbourne with the research to be undertaken at The Royal Women’s Hospital.
Dr Patrick Tan, The Royal Women’s Hospital, Melbourne
The project was awarded $A14,203 funding through the ANZCA research grants program for 2023.
We carried out this study to explore if it was possible and safe to provide high flow nasal oxygen therapy to labouring patients using a potent pain relief medication called remifentanil. When given via a button controlled pump (PCA) method, remifentanil provides good pain relief without the need for an epidural. However, it has major side effects including loss of oxygen levels to patients. High flow nasal oxygen is a modern method of delivering oxygen through soft nasal tubes with special properties that may be able to prevent unsafe oxygen drops caused by remifentanil PCA. We wanted to find out whether using high flow nasal oxygen could reduce this risk and, in doing so, make remifentanil PCA a safer option for more women during labour.
The study’s original design was to explore this treatment in patients undergoing labour during a medical termination of pregnancy or stillbirth. The already unimaginable labour pain experience of this vulnerable group of our patients is amplified by the emotional overlay of the devastating situation. Due to complications enrolling this group to the study, we pivoted to recruit pregnant patients expecting live births. Unfortunately, this was also met with barriers to entry, including the "dual-novelty" of introducing a potent drug and a new delivery technique simultaneously and the fastchanging nature of labour. Although we were unable to complete the study as initially intended, the experience clearly highlighted the practical challenges and barriers to conducting research in the obstetric setting. These insights are valuable for shaping future study designs and identifying better ways to support research participation in this dynamic and time-critical environment.
This oxygen delivery method has not been previously studied in these groups (labouring patients experiencing stillbirth, medical termination, or expecting live birth). The main finding of this study is that it is not feasible in our hospital context. Although the original research question remains important and unanswered, the study has provided valuable insights. We have a clearer understanding of the practical barriers making it difficult for patients to participate in research during labour. These lessons can be useful in the design of future studies which may be better suited to an institution with an existing remifentanil PCA program.
Presentations
“High flow nasal oxygen in pregnant women” – PhD Completion Seminar (February 2026) – P Tan
Full manuscript drafted - publication submission planned