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My Research

Current Project


Improving the Use of Public Access Defibrillation in the Response to Out-of-Hospital Cardiac Arrest


This project has been funded: I am an NIHR-funded Doctoral Research Fellow as of November 2017. Protocols for Work Packages 1 and 2 will appear soon.

Project Abstract

Approximately 28,000 people suffer an out-of-hospital cardiac arrest each year in England. Fewer than 8% survive to hospital discharge, but the Department of Health aspires to save 1000 extra lives every year by improving survival by 50%. Early defibrillation is key, with 70% survival possible if defibrillation occurs within 2 minutes of collapse. However, an ambulance will reach a victim within 8 minutes in only two-thirds of cases.

Public Access Defibrillation is the term given to the use of Automated External Defibrillators (AED) by members of the public before the arrival of the ambulance service. Public Access Defibrillation was used in just 2.4% of out-of-hospital cardiac arrests in England in 2014, greatly limiting its benefit at a population level.

The important role of the ambulance service in the dispatch of AED is recognised in international resuscitation guidelines. Ambulance services have databases of public-access AED that are integrated with Computer Aided Dispatch systems, but evidence suggests that bystanders making 999 calls are often not directed to nearby AED.

GoodSam is a mobile-phone, app-based alerting system allowing notification of trained volunteers to nearby cardiac arrests. The location of the cardiac arrest, as well as nearby AED, are displayed graphically. The volunteer can then attend, with or without an AED, and provide assistance. GoodSam is linked directly to London Ambulance Service dispatch systems and is activated automatically when a cardiac arrest is suspected by the 999 call-handler. This linkage between public and ambulance service is one potential way of improving AED use in cardiac arrest.

In this project the aims are to:


1. Identify the current and potential use of AED by GoodSam volunteers (Nov 2017 - Sep 2018).

The following will be investigated: proportion of out-of-hospital cardiac arrests when a GoodSam volunteer was activated, proportion (overall and in just GoodSam volunteer-activated cases) of cardiac arrest victims who had an AED applied, and survival to hospital discharge (overall and in GoodSam cases)

The potential for AED use in the GoodSam system will be determined by mapping cardiac arrest and AED locations, and calculating what proportion of cardiac arrests occur within a range of specified distances of an AED (from 100m to 500m).


2. Identify the barriers to AED use by GoodSam volunteers, and develop an intervention to increase AED use (Nov 2017 - Feb 2019).

Epidemiological factors, including characteristics of the cardiac arrest victim, volunteer- and AED availability, will be entered into a multiple logistic regression model to identify their contribution to AED use.

Organisational, technical and behavioural factors affecting AED use will be identified by brief interviews with GoodSam volunteers that receive a cardiac arrest notification and with people instrumental in setting up the technical interface between GoodSam and London Ambulance Service. Interviews will be coded and analysed using the Theoretical Domains Framework. Barriers to AED use will be categorised and potential interventions to overcome these barriers will be identified.


3. Identify if providing specific instructions to GoodSam volunteers to retrieve an AED affects the rate of AED use (Feb 2019 - Oct 2020).

The decisions that GoodSam volunteers make play an important part in determining whether an available AED is retrieved and taken to the patient. A feasibility randomised controlled trial will investigate whether providing specific instructions to volunteers to retrieve an available AED affects how often they are used. This small-scale trial will focus on process outcomes, but will guide a future multi-centre randomised controlled trial to determine whether AED use and survival to hospital discharge can be improved.

This project will provide critical insights into the potential for AED use and represents a huge opportunity to improve cardiac arrest survival within the next five years.