London, Jun 14 (IANS): Drones carrying defibrillators may help save lives of heart attack victims -- by delivering a dose of electric current -- four times faster than the time taken by an ambulance to reach the spot, researchers say.

Out-of-hospital cardiac arrest has low survival, with reducing time to defibrillation as the most important factor for increasing survival.

For every minute that passes between a person collapsing due to cardiac arrest and defibrillation, the chances of survival decrease by 10 per cent, the study said.

In the study, published by JAMA, the researchers simulated an out-of-hospital cardiac arrest, and found that drones carrying an automated external defibrillator arrived in less time than emergency medical services, with a reduction in response time of about 16 minutes.

"Saving 16 minutes is likely to be clinically important. Nonetheless, further test flights, technological development, and evaluation of integration with dispatch centres and aviation administrators are needed," said Andreas Claesson, from the Karolinska Institute, in Sweden.

An eight-rotor drone was developed and certified by the Swedish Transportation Agency. It was equipped with a defibrillator (weight 1.7 lbs), a global positioning system (GPS), a high-definition camera and integrated with an autopilot software system.

The drones were activated by a dispatcher and sent to a particular address with the defibrillator -- that are designed to give spoken instructions so that any bystander can use them, further reducing the response time.

The drones responded to 18 simulated cardiac arrests within a six-mile radius of their base, beating the ambulance every time with a median reduction in response time of 16:39 minutes.