Condition category
Pregnancy and Childbirth
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status

Plain English Summary

Background and study aims
Epidurals can result in serious complications. These include infections of the spine spinal and injury to nerves in the spine. About 1% of patients who have an epidural suffer what is called a post-dural puncture headache, a headache that develops after injection of an epidural. This can be extremely disabling. The risks of injury in very overweight (obese) women are increased due to technical difficulties. Changes to the training structure of the junior anaesthetists giving the injection and also the need for compliance with the European Working Time Directive (resulting in reduced training opportunities) further worsen this situation. Here, we want to find out about the pressure required to reach the epidural space when inserting an epidural needle into pregnant women of varying weights. Correlation will then be made with ultrasound and Magnetic Resonance Imaging (MRI) scans of their lower spine. The plan is to use the results gained to create a computer graphics and physical epidural injection simulator. This simulator will be used by anaesthetists to practice the epidural technique before performing on pregnant women.

Who can participate?
The study aims to recruit pregnant women with body mass indices (BMIs) that fall within four groups: 18-24.9; 25-34.9; 35-44.9 and over 45. The women will be recruited before they go into labour and also in early labour if they have expressed a desire to have an epidural. .

What does the study involve?
BMI will be calculated using height and weight.The women will be grouped accordingly. An ultrasound scan of the lower back will be performed before insertion of the epidural. If the woman then requests an epidural, the pressure applied to the epidural needle will be measured using a specific sensor attached to the needle. As the anaesthetist inserts the epidural, the change in pressures will be recorded wirelessly and the data transmitted to a distant computer. Following the epidural procedure, an MRI scan of the lower spine will be performed within 72hrs of the patient giving birth and these images will be used for computer animation modelling. This will be performed at a convenient time for the mother following delivery of the baby.

What are the possible benefits and risks of participating?
There will be no immediate benefits to those taking part but the data collected will be used to help to train future anaesthetists acquire the skills and knowledge for epidural insertion. The equipment used comes from standard sterile epidural packs and the pressure sensing device uses a three-way tap that also comes from a sterile pack. Due to the addition of this extra piece of equipment there is a theoretical increased risk of infection, although this is extremely small. However, please bear in mind that the risk of infection following an epidural ranges from 1 in 80,000 to 1 in 300,000. Ultrasound and MRI scans are non-invasive, painless procedures and are considered harmless.

Where is the study run from?
The study has been set up by Poole Hospital NHS Foundation Trust, UK. Poole Maternity Unit will be where the practical elements of the research will occur.

When is study starting and how long is it expected to run for?
The recruitment started in September 2012 and lasted for one year.

Who is funding the study?
National Institute of Academic Anaesthesia, UK.

Who is the main contact?
Prof Michael Wee,
Dr Richard Isaacs,

Trial website

Contact information



Primary contact

Prof Michael Wee


Contact details

Dept of Anaesthesia
Poole Hospital NHS Foundation Trust
BH15 2JB
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Quantification of the pressures generated during insertion of an epidural needle and subsequent imaging of the epidural space in labouring women of varying body mass indices


Study hypothesis

The primary aim is to measure the resultant pressure exerted on an epidural needle as it is advanced through the interspinous ligament and ligamentum flavum of parturients with increasing body mass indices.

Ethics approval

NRES Committee South Central - Portsmouth, 13/06/2011, ref: 11/SC/0196

Study design

Single-centre observational study

Primary study design


Secondary study design

Cohort study

Trial setting


Trial type


Patient information sheet

The patient information sheet is available upon request


Epidural anaesthesia


This study will only involve women who have requested to have an epidural as part of their birth plan. All of the epidural procedures will be carried out on the labour ward of Poole Maternity Unit by two experienced anaesthetists using standard equipment. To collect the pressure data we will attach a small electronic sensor onto the epidural needle. As the anaesthetist advances the needle through the ligaments, the electronic sensor will pick up the pressure readings and transfer data wirelessly back to a computer or recording device. An ultrasound of the lower spine will also be performed prior to the epidural, followed by a magnetic resonance imaging (MRI) scan of the spine after delivery. This data will also be used to create the epidural simulator based on patient-specific measurements. These measurements and images will lead to the development of a novel epidural simulator to help train novice and experienced anaesthetists with difficult epidurals.

Intervention type



Not Applicable

Drug names

Primary outcome measure

The primary aim is to measure the pressures required to reach the epidural space when inserting an epidural needle into pregnant women of varying body mass indices. Graphical displays of the pressures will then be produced.

Secondary outcome measures

Correlation will then be made with ultrasound and Magnetic Resonance Imaging (MRI) scans of their lower spine. The aim will be to create a computer graphics and physical epidural injection simulator. This simulator will be used by anaesthetists to practice the epidural technique in a controlled environment.

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. ASA I or II (healthy) women aged 18-40 inclusive
2. Women having first child or any subsequent children (primi and multiparous)
3. Women in early active labour or prior to induction of labour who have requested epidural
analgesia or been advised by the medical team to have an epidural
4. Singleton pregnancies (i.e. not twins etc)

Participant type


Age group




Target number of participants


Total final enrolment


Participant exclusion criteria

1. Any of the usual contraindications to epidural anaesthesia
2. Known spinal abnormalities
3. Previous back surgery
4. History of connective tissue disorder
5. Difficult epidural insertion requiring more than 3 attempts
6. Women who already have an epidural in-situ and need a re-site for inadequate block
7. Women with inadequate comprehension of the English language and poor communication

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Dept of Anaesthesia
BH15 2JB
United Kingdom

Sponsor information


Poole Hospital NHS Foundation Trust (UK)

Sponsor details

Longfleet Road
BH15 2JB
United Kingdom

Sponsor type

Hospital/treatment centre



Funder type

Research organisation

Funder name

National Institute of Academic Anaesthesia (UK) (Obstetric Anaesthetists' Association Large Project Grant) July 2012 (ref: WKR0-2012-0035)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

2017 results in 10.29328/journal.hacr.1001004 (added 19/02/2020)

Publication citations

Additional files

Editorial Notes

19/02/2020: The following changes have been made: 1. Publication reference added. 2. The final enrolment number has been added from the reference. 11/05/2017: No publications found in PubMed, verifying study status with principal investigator