An innovative method for enhancing bystander defibrillation during out-of-hospital cardiac arrests entails the rapid dispatch and transport of an automated external defibrillator (AED) by drone directly to the location of the suspected arrest. This study evaluated the proportion of cases in which drone delivery of an AED could precede ambulance arrival and determined the median time advantage gained through such drone-assisted deliveries. In this prospective observational investigation, five drones fitted with AEDs were stationed across two designated controlled airspaces in Sweden, encompassing a population of approximately 200,000 residents. These drones were activated concurrently with routine emergency medical services for alerts involving suspected out-of-hospital cardiac arrests and operated autonomously. Dispatches excluded incidents concerning children under 8 years of age, trauma-related events, and arrests observed by emergency medical personnel. Further exclusions applied when air traffic control denied flight permission, weather conditions were unsuitable, no-delivery zones were present, or operations occurred after dark. Information was sourced from dispatch centers, ambulance providers, the Swedish Registry for Cardiopulmonary Resuscitation, and the drone operating team. The main endpoints were the percentage of incidents achieving AED delivery by drone before ambulance arrival and the median time difference (expressed in minutes and seconds) between drone AED delivery and ambulance on-scene arrival. Secondary exploratory measures included the rate of drone-delivered AED attachment before ambulance arrival and the proportion of cases involving defibrillation with a drone-supplied AED when used before ambulance response. From April 21, 2021, to May 31, 2022, 211 suspected out-of-hospital cardiac arrest notifications were issued, resulting in drone deployment for 72 (34%). Successful AED delivery occurred in 58 (81%) of deployed missions; the predominant cause of non-delivery was dispatch center cancellation after determining the event was not a genuine out-of-hospital cardiac arrest. For the 55 cases with complete arrival time data for both drone and ambulance, the drone delivered the AED before ambulance arrival in 37 instances (67%), producing a median time advantage of 3 min and 14 s. Within this subset, 18 (49%) were confirmed true out-of-hospital cardiac arrests, and attachment of the drone-delivered AED occurred in six (33%) of these. Two cases (33%) presented with a shockable initial rhythm and received defibrillation via the drone-delivered AED before ambulance arrival, including one individual who survived to 30 days. The study recorded no adverse events. In 91% of deliveries, the AED was positioned (before final landing) within 15 m of the patient or the relevant building. Drones carrying AEDs, when activated for suspected out-of-hospital cardiac arrests, delivered the devices ahead of ambulance arrival in approximately two-thirds of applicable cases, providing a clinically significant median time saving of over 3 minutes. Such a system may help shorten the delay to AED attachment in the period preceding ambulance response.
