Authors' objectives: Ambulance services treat over 32,000 patients sustaining an out-of-hospital cardiac arrest annually, receiving over 90,000 calls. The definitive treatment for out-of-hospital cardiac arrest is defibrillation. Prompt treatment with an automated external defibrillator can improve survival significantly. However, their location in the community limits opportunity for their use. There is a requirement to identify the optimal location for an automated external defibrillator to improve out-of-hospital cardiac arrest coverage, to improve the chances of survival. Annually, English ambulance services treat over 30,000 people who have sustained an out-of-hospital cardiac arrest (OHCA), about 25% of whom achieve a return of spontaneous circulation by the time of hospital handover and 8.5% survive to 30 days. The chain of survival shows the essential elements required in an emergency care system to improve outcomes from an OHCA. The first two links – early recognition and early cardiopulmonary resuscitation – can buy time for the OHCA patient but are not definitive treatments in themselves. The key and most effective treatment for an OHCA is defibrillation. Prompt treatment with an automated external defibrillator (AED), within 3–5 minutes of collapse, can lead to survival rates in excess of 50%. Public-access defibrillation (PAD) refers to the use of AEDs by members of the public. PAD programmes allow the community access to this life-saving intervention while waiting for ambulances to arrive. The importance of PAD is growing given the increasing demands on ambulance services that are making reaching OHCAs in a timely manner challenging. However, at present, only a small proportion of patients are treated by PAD (5%). A fundamental, structural barrier, which limits opportunity for the use of AEDs, is their location in the community. There has been no clear strategy in the UK on where AEDs should be placed; the choice of where to install them in public places has been driven mainly by local ad hoc initiatives. This approach is limited and there is a call for an evidence-based strategy, and a requirement to identify the optimal location for an AED to improve OHCA coverage, to improve the chances of survival. The primary objective of this study was to optimise the placement of public-access AEDs in England, using mathematical modelling techniques, to maximise the likelihood that an individual sustaining an OHCA will have access to PAD, improving their chances of survival. The secondary objective was to assess the cost-effectiveness of optimised public-access AED placement compared to current and alternative-placement strategies.

Authors' results and conclusions: Historical out-of-hospital cardiac arrests occurred in more deprived areas and automated external defibrillators were placed in more affluent areas. The median out-of-hospital cardiac arrest – automated external defibrillator distance was 638 m and 38.9% of out-of-hospital cardiac arrests occurred within 500 m of an automated external defibrillator. If an automated external defibrillator was placed in all points of interests, the proportion of out-of-hospital cardiac arrests covered varied greatly. The greatest coverage was achieved with cash machines. Coverage loss, assuming an automated external defibrillator was not available outside working hours, varied between points of interest and was greatest for schools. Dividing the country up into 1 km2 grids and placing an automated external defibrillator in the centre increased coverage significantly to 78.8%. The optimisation model showed that if automated external defibrillators were placed in each points-of-interest location out-of-hospital cardiac arrest coverage levels would improve above the current situation significantly, but it would not reach that of optimisation-based placement (based on grids). The coverage efficiency provided by the optimised grid points was unmatched by any points of interest in any region. An economic evaluation determined that all alternative placements were associated with higher quality-adjusted life-years and costs compared to current placement, resulting in incremental cost-effectiveness ratios over £30,000 per additional quality-adjusted life-year. The most appealing strategy was automated external defibrillator placement in halls and community centres, resulting in an additional 0.007 quality-adjusted life-year (non-parametric 95% confidence interval 0.004 to 0.011), an additional expected cost of £223 (non-parametric 95% confidence interval £148 to £330) and an incremental cost-effectiveness ratio of £32,418 per quality-adjusted life-year. The stakeholder meeting agreed that the current distribution of registered publicly accessible automated external defibrillators was suboptimal, and that there was a disparity in their location in respect of deprivation and other health inequalities. We have developed a data-driven framework to support decisions about public-access automated external defibrillator locations, using optimisation and statistical models. Optimising automated external defibrillator locations can result in substantial improvement in coverage. Comparison between placement based on points of interest and current placement showed that the former improves coverage but is associated with higher costs and incremental cost-effectiveness ratio values over £30,000 per additional quality-adjusted life-year. The study looked at the location of 147,278 historical OHCAs (2014–9) and 32,491 AEDs, and 14 potential POIs. Automated external defibrillators are potentially life-saving devices for people who sustain an OHCA. AEDs need to be placed intelligently in public settings so that they are likely to be used by bystanders. We have developed a data-driven framework to support public-access AED location decisions, using optimisation and statistical models. We applied the methodology to real data from England. Results have demonstrated that optimising AED locations can result in substantial improvement in coverage compared to the current approach to AED deployment. We developed a de novo decision-analytic model to determine the costs and benefits associated with AED placement strategies in each of the different POIs and compared these against current AED placement. Results of the economic analysis showed that all of the alternative placements considered were associated with ICERs above £30,000 per additional QALY.

Authors' methods: This was a secondary analysis of data collected by the Out-of-Hospital Cardiac Arrest Outcomes registry on historical out-of-hospital cardiac arrests, data held on the location of automated external defibrillators registered with ambulance services, and locations of points of interest. Walking distance was calculated between out-of-hospital cardiac arrests, registered automated external defibrillators and points of interest designated as potential sites for an automated external defibrillator. An out-of-hospital cardiac arrest was deemed to be covered if it occurred within 500 m of a registered automated external defibrillator or points of interest. For the optimisation analysis, mathematical models focused on the maximal covering location problem were adapted. A de novo decision-analytic model was developed for the cost-effectiveness analysis and used as a vehicle for assessing the costs and benefits (in terms of quality-adjusted life-years) of deployment strategies. A meeting of stakeholders was held to discuss and review the results of the study. Ethics and regulatory approvals Following Health Research Authority guidelines, the study did not require formal NHS Research Ethics Committee approval. The study was approved by the University of Warwick’s Biomedical and Scientific Research Ethics Committee (BSREC 118/18-19). The project was co-sponsored by the University Hospitals Birmingham NHS Foundation Trust and the University of Warwick. The Out-of-Hospital Cardiac Arrest Outcomes (OHCAO) registry has approval from the Confidentiality Advisory Group to collect and process identifiable patient information where it is not practical to obtain consent (22CAG0072 and 22CAG0087). Ethics approval for the OHCAO registry was gained from the National Research Ethics Committee South Central (13/SC/0361). This was a secondary analysis of data that were collected by the OHCAO registry on historical OHCAs, data held by ambulance services on the location of AEDs registered with them, and locations of points of interest (POIs) available from Ordnance Survey. Also, data were obtained on the census neighbourhood characteristics of areas of England. The study was divided into four work packages (WPs): (1) exploration of the characteristics and coverage of current locations of AEDs relative to the location of historical OHCAs; (2) comparison of the OHCA coverage of various AED deployment strategies (POIs and grid-based) and an optimisation model with the current coverage; (3) determination of the cost-effectiveness of the strategies in WP2 compared to current placement (CP); and (4) development of a national consensus of the optimal location for public-access AEDs.

Project Status: Completed

URL for project: https://www.journalslibrary.nihr.ac.uk/programmes/hsdr/NIHR127368

Year Published: 2025

URL for published report: https://www.journalslibrary.nihr.ac.uk/hsdr/HTBT7685

URL for additional information: English

English language abstract: An English language summary is available

Publication Type: Full HTA

Country: England, United Kingdom

DOI: 10.3310/HTBT7685

Organisation Name: NIHR Health Services and Delivery Research programme

Contact Address: NIHR Journals Library, National Institute for Health and Care Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK

Contact Name: journals.library@nihr.ac.uk

Contact Email: journals.library@nihr.ac.uk