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Out-of-Hospital Cardiac Arrest Outcomes (OHCAO)

Photograph of the front of ambulances parked in depot

Key information

Title: Out-of-Hospital Cardiac Arrest Outcomes (OHCAO)

Chief Investigator: Professor Gavin Perkins

Sponsor: Warwick Medical School, National Ambulance Service Medical Directors

Funder: British Heart Foundation, Resuscitation Council UK

Registration Number: ISRCTN10428536


Cardiac arrest is the term used to describe sudden cessation of heart function. After cardiac arrest occurs, blood stops being circulated to the vital organs and consciousness is lost within seconds. Unless resuscitation is started promptly death will occur within a few minutes. Each year about 30,000 people receive resuscitation for an Out-of-Hospital Cardiac Arrest (OHCA) in the United Kingdom (UK). Only one in every ten people that have a cardiac arrest survive to go home from hospital.

Information collected by the Department of Health has shown large differences in the number of people that survive an OHCA depending on where they live. In simple terms people in some parts of the country are twice or three times more likely to survive than in other areas.

This project is working with UK Ambulance Services to try and find out the reasons behind such big differences in survival. It has developed a standard way of collecting information about OHCA and for finding out if a resuscitation attempt was successful.

The study uses existing information collected by ambulance services during the course of their routine duties. Information about individuals that receive resuscitation for OHCA will be securely transferred to researchers at the University of Warwick.

The information will be used to obtain a better understanding of why survival rates vary so widely. It will work out which are the most effective treatments and help ambulance services improve the quality of care for victims of OHCA.

The project has received approvals from both the National Research Ethics and Confidentiality Advisory Group to collect sensitive data via the secure web server. Only data that has been mapped/transformed and agreed by the Trusts will be imported.

Sample size:

OHCAO is a prospective study, collecting information on all out-of-hospital cardiac arrests in the UK.

Data is provided by the Ambulance Services.

Primary outcome:

Survival at 30 days.


Current funding to 31st October 2028.

National Data Opt-Out (NDO):

Non-Research activities

Since July 2022 we have permission from the Confidentiality Advisory Group (CAG) to hold and use everyone’s data for quality improvement work for the NHS or to inform health policy and patient safety.

Data used for Quality Improvement work for NHS or to inform health policy is defined by CAG as a non-research activity. An exemption from applying the NDO for this work has been granted by CAG.

Non-Research activities include the Annual Epidemiology Reports, NHS England’s Ambulance Service Quality Indicators (AQI’s) & the OHCAO Map.

For more information about non research projects use the links below:


An anonymised research database is being created for research projects. The anonymised research database will not contain any personal identifiable data and new derived variables created to eliminated risk of reidentification.

Further information on how data are used can be found in our data privacy notice.


Search the OHCAO website:


Tel: 02476 572725


Warwick Clinical Trials Unit
Warwick Medical School
University of Warwick
Gibbet Hill Road

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