POSED
Research type
Research Study
Full title
A feasibility study of Prehospital Optimal Shock Energy for Defibrillation (POSED)
IRAS ID
277693
Contact name
Gavin D. Perkins
Contact email
Sponsor organisation
University of Warwick
ISRCTN Number
ISRCTN16327029
Duration of Study in the UK
2 years, 7 months, 30 days
Research summary
Research Summary:
Each year, the UK ambulance services attempt to restart the hearts of 30,000 people who have suffered cardiac arrest (when the heart stops beating). Currently, less than 10% of people survive. Performance of good chest compressions (CPR) and, where appropriate, delivery of an electric shock to the heart (defibrillation) are the only proven methods of reviving these patients. Defibrillators (electric shock machines) can deliver a range of shock strengths (low, medium or high). Because we don’t currently know the best shock strength to deliver, there is variation between UK ambulance services. If we can find the best shock energy levels, we can restart hearts more quickly and save more lives.
POSED is a feasibility study, which will help researchers to make good decisions about a full-scale trial to make sure that time and money would be well spent. This involves: • Putting patients into different groups to receive different shock strategies. All of these shock strengths are currently used in UK ambulance services. • Finding the ‘recruitment rate’ by comparing the number of patients included with the number who could have been included (from 999 call records). • Tracking patients’ condition in hospital for the following 30 days.
I aim to include 90 patients who have been treated for cardiac arrest in this study. All surviving patients will be invited to take part in the follow up which happens 30 days after the cardiac arrest. This will involve a research paramedic scoring how well they have recovered either by talking with the patient or by reading their medical notes.
I will speak to ambulance staff to explore how to improve processes so that a full clinical trial would work.Summary of Results:
A feasibility study of Prehospital Optimal Shock Energy for Defibrillation (What is the best shock energy for defibrillation?)
Sponsored by: University of Warwick
Funded by: NHS England/National Institute for Health and Social Care Research• Why was the research needed?
Cardiac arrest, when the heart stops pumping blood around the body, can happen suddenly and unexpectedly. We know that the treatments proven to resuscitate patients are chest compressions, known as cardiopulmonary resuscitation (CPR), and electric shocks to the heart, known as defibrillation. Defibrillators can deliver a range of electric shock energies (low, medium or high) but we don’t know the best energy level for these shocks.
Too little energy may fail to defibrillate the heart whilst too much energy may damage it. Since the best energy level is not known, different UK Ambulance Services currently give different shock energies (low, medium or high) depending on local protocols.• Main research question:
Is it feasible to conduct a large clinical trial to find out the best shock energy to be applied by a defibrillator?• Where and when did the feasibility study take place?
This study involved a single UK ambulance service (South Central Ambulance Service). Adult patients in Berkshire and Oxfordshire were included in the study between March 2022 and February 2023.• What happened during the feasibility study?
Forty-nine ‘study’ defibrillators, that were pre-set with one of three shock energy strategies randomly allocated to ambulances and used by the crews when responding to a cardiac arrest. None of these shock strengths were any higher or lower than currently used across the various UK ambulance services. All other treatments and care were given in the usual way. Patient outcome was compared according to shock energy used.• What were the results of the feasibility study?
1. The feasibility study comprised of 38 patients who were treated with a ‘study’ defibrillator. The study showed that each defibrillator in the study would include 0.84 patients per year. This will help us to work out how long a full trial would take and how many defibrillators would be needed.2. Of the cardiac arrest patients attended by ambulance crews taking part in the feasibility study, 88% received the shock energy from a ‘study’ defibrillator. (All other patients received shock energies that are currently used in the UK ambulance services).
3. 3. We were able to find out in 95% of cases whether patients had survived until 30 days after they were treated. In 3 cases we could not find out whether patients were left with any disabilities following their cardiac arrest.
4. It was harder than expected to collect data from the defibrillators as these were carried on busy working ambulances. (Remote upload of data would be more effective in a full clinical trial)
5. We found that ‘study’ defibrillators were sometimes swapped between ambulances. This meant that four patients we thought were included in the study turned out not to be. We plan to keep the defibrillators on their correct ambulances for a full trial and have identified ways to achieve this.
• How has this feasibility study helped patients and researchers?
When the effects of different treatments are not known, researchers may conduct a clinical trial to find out. Trials of this type are usually large and expensive, so it is essential to first determine whether these trials are possible and pre-empt any identified problems. Such a study helps to ensure that time and money will be well spent on a full-scale trial.• How were patients and public involved in the research?
Six members of the public advised and oversaw the activities of the research team. They helped us to make information leaflets and letters easy to read and understand. They told us what was important to patients and their relatives and helped us to come up with a plan when we found that defibrillators were being moved between ambulances.• Details of any further research planned
We plan to apply for funding a full-scale trial. We will use the lessons learnt from this feasibility study to design a trial that can work well.• Where can I find further info?
At our website: https//warwick.ac.uk/fac/sci/med/research/ctu/trials/posedAPPENDIX
Fibrillation and Defibrillation
Following a complete cessation of activity in the heart there can be no recovery.
However, during fibrillation the chambers of the heart move in a chaotic way that fails to pump blood around the body. This is a cardiac arrest that may be treatable with defibrillation.
By administering a controlled electric shock (defibrillation) the heart is stopped so allowing a possible restoration of the normal rhythm.https://gbr01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fu2790089.ct.sendgrid.net%2Fls%2Fclick%3Fupn%3DXv3JSvJ-2B3M71ppf7N9agbfBkV8STyx-2BNg3HoA191NauiGjGaT29Vn7GnXWURLjjhkPPTYfeBhX-2F0iswa3i47f-2BrgKz0j5s-2FKc-2B8bBvZ314I-3DpwrN_E1aO2-2BZlVOSJJV-2FajQqskegTd6IRomHYTi-2Fbt8SH3YIQcWpfrbLJCCnc7FMcdQ4PHuC2Dxu07cxaFupUIr0mFr-2B3vZ2VOTjS5ACRz52Qvd-2F1xmfI4sSPb1d-2Fz0r2ud04UDDCuZ3dt1oKwI-2BIcnRsCDpNENonCKnAYtDbFpRhY5UENFunqk3xx3MDAKZ6ByxIi4CMk-2FQAVGSvhla8yspIOQ-3D-3D&data=05%7C02%7Charrow.rec%40hra.nhs.uk%7C720c2f74e8854871d43b08dc27b687a2%7C8e1f0acad87d4f20939e36243d574267%7C0%7C0%7C638428912112257939%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=1EdkF%2BCJIblmd6JXxEtXCWevgEjc6v27DU6BVG3pEVc%3D&reserved=0
REC name
London - Harrow Research Ethics Committee
REC reference
20/LO/1242
Date of REC Opinion
20 Jan 2021
REC opinion
Further Information Favourable Opinion