Time to Delivery of an Automated External Defibrillator Using a Drone for Simulated Out-of-Hospital Cardiac Arrests vs Emergency Medical Services

Out-of-hospital cardiac arrest (OHCA) affects approximately 55 of 100 000 inhabitants per year in the United States, with low survival (8%-10%).¹ Reducing time to defibrillation is the most important factor for increasing survival in OHCA.^2,3

Unmanned aerial systems, commonly called drones, can be activated by a dispatcher and sent to an address provided by a 911 caller. The drone may carry an automated external defibrillator (AED) to the location of an OHCA so that a bystander can detach and use it. Theoretical geographical information system models have shown that drones carrying an AED can reduce response times in rural areas.^4,5 However, whether they reduce response times in a real-life situation is unknown. This study compared the time to delivery of an AED using fully autonomous drones for simulated OHCAs vs emergency medical services (EMS).

An 8-rotor drone (weight, 5.7 kg; maximum cruising speed, 75 km/h) was developed and certified by the Swedish Transportation Agency (Figure). It was equipped with a global positioning system (GPS) and a high-definition camera and integrated with an autopilot software system. Two licensed pilots sent GPS coordinates and routes to the drone using alternating telemetry over a 433 mHz and 3G network. The entire flight from takeoff to landing was autonomous, monitored by the dispatcher. For safety reasons, a second pilot was present at the landing site in telephone contact with the dispatcher to manually take over the descent if necessary.

The drone was equipped with an AED (FRED easyport, Schiller AG), weighing 763 g, and placed at a fire station in Norrtälje municipality north of Stockholm, which was chosen for characteristics (such as restricted airspace, extensive delay in EMS response times, and a heavy population in the summer) that might benefit from a drone system. The drone was dispatched for out-of-sight flights during a 72-hour period in October 2016, to locations where consecutive OHCAs within a 10-km radius from the fire station had occurred between 2006 and 2014 (times of day: 3:43 am and 6:48 pm). The OHCAs were identified through the Swedish Registry for Cardiopulmonary Resuscitation; only addresses and times to arrival of EMS were abstracted. The primary end point was time from dispatch to arrival of the drone at the scene of the OHCA compared with time for EMS. Flight permission was granted by the Swedish Transportation Agency and ethical approval by the ethical board in Stockholm, Sweden, with a waiver of informed consent.

The Mann-Whitney test (calculated with SPSS Statistics version 21 [IBM]) was used to compare times for drone vs EMS. A 2-sided P value less than .05 was considered significant.

Eighteen consecutive autonomous remotely operated flights were performed with a median flight distance of 3.2 km. The median time from call to dispatch of EMS was 3:00 minutes (interquartile range [IQR], 2:00-5:30). The median time from from dispatch to drone launch was 3 seconds. The median time from dispatch to arrival of the drone was 5:21 minutes (IQR, 3:03-8:33; shortest time, 1:15 minutes) vs 22:00 minutes (IQR, 17:48-29:00; shortest time, 5:00 minutes) for EMS (P < .001) (Table). The drone arrived more quickly than EMS in all cases with a median reduction in response time of 16:39 minutes (95% CI, 13:48-20:12; P < .001). No adverse events or technical issues occurred during any flights.

This preliminary study found that it was possible to autonomously transport and deliver an AED using a drone in out-of-sight flights. The drone arrived in less time than the EMS in all simulated cases. Therefore, drones carrying AEDs may reduce time to defibrillation in OHCAs. Saving 16 minutes is likely to be clinically important.^2,6 Nonetheless, further test flights, technological development, and evaluation of integration with dispatch centers and aviation administrators are needed.

Limitations include the small number of flights over short distances in good weather. The use of historical EMS times for comparison may not reflect contemporary differences, as traffic patterns may have changed since 2006-2014. The outcomes of OHCA using the drone-delivered AED by bystanders vs resuscitation by EMS should be studied.

Accepted for Publication: March 20, 2017.

Corresponding Author: Andreas Claesson, RN, PhD, Center for Resuscitation Science, Karolinska Institutet, Sjukhusbacken 10, 118 83 Stockholm, Sweden (andreas.claesson@ki.se).

Author Contributions: Dr Claesson had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Claesson, Bäckman, Ringh, Svensson, Djärv, Hollenberg.

Acquisition, analysis, or interpretation of data: Claesson, Bäckman, Svensson, Nordberg, Djärv, Hollenberg.

Drafting of the manuscript: Claesson, Bäckman, Svensson, Hollenberg.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Claesson, Svensson, Hollenberg.

Obtained funding: Claesson, Svensson, Hollenberg.

Administrative, technical, or material support: Claesson, Bäckman, Djärv, Hollenberg.

Supervision: Claesson, Ringh, Svensson, Nordberg, Djärv, Hollenberg.

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Funding/Support: This study was funded by the Stockholm city council innovation fund.

Role of the Funder/Sponsor: The Stockholm city council had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.