An autonomous drone has helped to save the life of a 71-year-old man who was suffering a cardiac arrest.

The drone delivered a defibrillator to a doctor helping the man, who became ill while shovelling snow outside his house in Trollhattan, Sweden.

The man, who didn't wish to be named, told the BBC it was "fantastic" that it arrived so quickly.

The company behind the drone says it meant that defibrillation could begin before the arrival of an ambulance.

Everdrone says it took just over three minutes from the alarm being raised until the Automated External Defibrillator (AED) was delivered.

Passing doctor
The patient told the BBC he doesn't remember what happened that day in early December.

He was clearing thick snow from his driveway but when the cardiac arrest hit, "everything went black", he said.

His wife later told him how lucky he had been.

Dr Mustafa Ali, who happened to be driving past at the time, rushed to help and told Everdrone: "I was on my way to work at the local hospital when I looked out the car window and saw a man collapsed in his driveway.

"The man had no pulse, so I started doing CPR while asking another bystander to call 112 (the Swedish emergency number).

"Just minutes later, I saw something flying above my head. It was a drone with a defibrillator."

Everdrone chief executive Mats Sallstrom believes the technology played a part in a team effort to save the patient's life.

"It's a medical doctor doing CPR, it's the early defibrillation, it's the treatment in the ambulance on the way to the hospital," he told the BBC.

"It's important to understand that there's a chain of events saving the person's life, and the drone is a very critical part of how that system works."

The drone is a partnership between the Karolinska Institutet - Sweden's largest medical university - together with the national emergency operator SOS Alarm, Region Vastra Gotaland and Everdrone.

In 2020, the group explored the use of drones to deliver defibrillators in Gothenburg and Kungalv in western Sweden.

Over the four-month study, the Karolinska researchers found that drones were dispatched to 12 out of 14 cases of suspected cardiac arrest, and successfully delivered an AED in all but one.

In seven cases the drones arrived before the ambulances.

In the December incident, it was fortunate that a doctor was nearby, but questions remain about whether members of the public without medical training would know what to do with a defibrillator.

In the 2020 study no devices were attached to patients, though the reasons why are unclear.

Mr Sallstrom said they are designed for an untrained person to use, adding: "In these scenarios you are also on the phone to the emergency centre and they can guide you."

Since 2020, Everdrone says the system has got a lot faster - the focus now is to work closely with the dispatchers who give instructions to the people on site.

Everdrone is in talks to bring the technology to other countries, including the UK - though the firm won't say to which ones it has been speaking.

Drones are already in use by some UK emergency services. Earlier this year, an 83-year-old man's family said his life was "saved" when he was found by a police drone after being missing for 18 hours.

Ready to go
The key to the Swedish system is having an integrated system ready to go, Everdrone says.

The drone system is electronically integrated with the emergency dispatch system and can get ready to fly as soon as an emergency call suggesting a cardiac arrest is received, Mr Sallstrom said.

Although the drone is autonomous, there is also a "pilot in command" - who oversees the operation for safety reasons and can obtain clearance to take off from air traffic control.

"This might seem like a huge process but roughly 60 seconds from the alarm we can be on our way," said Mr Sallstrom.

Time is very much of the essence, the chance of survival decreases by 7-10% with each minute following collapse, the company says.

And Everdrone believes eventually the system might be used to deliver other urgently needed medical devices.

The patient the drone helped save is certainly a fan. In his town, road congestion can be a problem, but the drones, he says, fly over the traffic.

"I'm very, very happy. I think it's fantastic that they came so quickly," he says.