Aug. 31, 2021 -- Drone delivery of an automated external defibrillator (AED) in real-life cases of suspected out-of-hospital cardiac arrest (OHCA) in a residential area in Sweden was safe and feasible, in a small clinical trial.
Importantly, when an AED-equipped drone arrived before an ambulance that had been dispatched at the same time — which occurred in 7 of 11 cases — there was a median time saving of 1 minute, 52 seconds.
However, a drone was dispatched in less than half of the suspected OHCA cases during this 4-month study and none of the AEDs was removed from the drones before the ambulance arrived.
"We would like to save even more time," Sofia Schierbeck, MD, said during a media briefing prior to the session at the European Society of Cardiology (ESC) Congress 2021. Schierbeck is also a PhD student at the at the Center for Resuscitation Science at the Karolinska Institute, Stockholm, Sweden.
"But we think this is a good start," she said. "We have shown that it is possible to deliver AEDs. That was our primary outcome."
Steen Dalby Kristensen, MD, professor and cardiologist, Aarhus University Hospital, Aarhus, Denmark, who chaired the press conference, pointed out that "two minutes is really quite important," since for cardiac muscle, every minute counts, and for the brain, every second counts.
The study was published online August 26 in the European Heart Journal to coincide with the meeting.
"Despite its small sample size, this study provides a proof of concept, confirming the feasibility of adding AED delivery by drones to the OHCA resuscitation arsenal," Nicole Karam, MD, Paris Sudden Death Expertise Center (SDEC), France, and colleagues summarized in an accompanying editorial.
"However, it also shows the importance of further improvement in the functionality of drones, careful selection of OHCA cases in which a drone should be used and educating bystanders regarding AED use."
"Our goal for the drone-delivered AEDs is that they will be a complement to the ambulance and that they will be attached to patients and help save lives," Schierbeck says.
For "each minute without treatment with CPR and a defibrillation to the heart, the chance of survival decreases by 7% to 10%," she notes , so "if we could decrease time to defibrillation by this intervention by only a few minutes, this could have a great impact."
The researchers have started a follow-up study with four drones.
"In a few years, drones used to deliver emergency equipment, such as AEDs, could be common practice," Schierbeck says.
Promising 'Real-Life' Drone Flights
Of 6,000 OHCAs each year in Sweden, only 10% of patients survive; 71% of arrests occur in people's homes, and the average ambulance response time is 11 minutes, Schierbeck noted.
Therefore, "drones could theoretically decrease time to defibrillation," she says.
The researchers conducted a live feasibility trial from June through September 2020, in a 125 square-km area with about 80,000 inhabitants, in airspace controlled by Säve Airport, Gothenburg, Sweden.
Three automated hangars each contained a 12.5 kg AED-equipped, remotely operated drone with Everdrone software and hardware that could travel up to 5 km (3.1 miles) and was controlled by a trained operator in a mission-control center.
An AED was successfully delivered in 55 of 61 test flights (90%), that were also part of the study.
However, in one of the test flights, a parachute was incorrectly activated (false positive), so the real-life drone operation was halted for 21 days to investigate this.
Of the 53 phone calls to 1-1-2 (the emergency phone number in Sweden) for suspected OHCA in the test area during the real-life study, an AED-carrying drone was not dispatched in 39 cases — due to halted flight operation in 11 cases, drone maintenance in one case, routes above dense population in 8, no-fly zones in 8, rain or wind greater than 30 km/hour (19 miles/hour) in 9, darkness in 1, and failure to alert a drone also in 1.
Of the 14 cases that were eligible for an AED-equipped drone flight, 12 drones passed the automated pre-flight safety checks and were dispatched.
AED delivery was successful in 11 of the 12 cases where drones were dispatched (92%), apart from one case of a post take-off safety landing.
The median distance from a drone hangar to a suspected OHCA was 3.1 km (1.9 miles), and the AED was delivered at a median distance of 9 meters from the patient.
The median time from the 112-call until an AED was delivered to the OHCA site was 9.08 minutes for drone delivery vs 9.53 minutes for ambulance arrival.
No AEDs were damaged, and no adverse events occurred during the real-life flights.
Follow-up Study Will Address Limitations
"If a more systematic use of drones in OHCA is to be considered, their performance has to be improved in order to limit the circumstances in which they cannot take off, especially poor weather conditions and darkness," Karam and colleagues wrote, noting that no-fly zones prohibiting drone use also need to be reduced.
In the future, a dispatcher could estimate ambulance travel time delays because of traffic, weather, and road configurations, to see if sending an AED by a drone would be more efficient, they suggested.
However, "besides increasing the time gain, we also need to work on educating bystanders regarding AED use, to improve the efficiency of this strategy," they wrote.
The researchers agreed. They now have permission to deploy the drones in the dark and also to fly over densely populated areas, Schierbeck says, which means that they can use a more direct flight route and include more cases.
The current drone flight distance is limited by battery life.
"However, drone technology develops quickly all the time," she says. The researchers expect that the AED-equipped drones will soon be able to fly faster, longer, and in poor weather conditions.