The theft of eight defibrillator units installed across the greater Bristol area is being investigated by police.
The units were taken during December from sites including Pucklechurch, Frenchay, Fishponds and Easton.
Clive Setter who campaigned to get the defibrillators in the area said 12 had been used 36 times in the last eight months according to ambulance figures.
Defibrillators are used to deliver a shock to restart a patient’s heart when they are in cardiac arrest.
“We know that without them lives will be lost,” said Mr Setter.
“It’s hard to think why someone would take something which could be so important to someone having a cardiac arrest.”
Community groups who raised money to fund the equipment said they were now considering installing CCTV cameras.
“South West Ambulance say they have to be accessible 24/7,” said Ray Care, chairman of the Bristol Area Cardiac Support Group.
Keith Porter, from Yate, who survived a massive heart attack in 2013, said the machine installed near his home and used on him helped save his life.
“I wouldn’t be here today without it,” he said.
“They’re playing with people’s lives, it’s life saving treatment on the spot.”