Helping someone survive a cardiac arrest is not always going to be the job of a medical expert — it could be down to you.

Each year, more than 20,000 Australians suffer a sudden cardiac arrest, but according to Australian medical authorities only about 10 per cent of those people survive.

St John Ambulance Australia said its figures showed the survival rate was more like 5 per cent.

Either way, that is far too many lives being lost each year, especially given that the issue is fundamentally one of response time.

Two years ago Ellie Bayliss, 30, was standing on a Sydney railway station when her heart stopped beating.

Luckily for her, a rail paramedic was on the same platform, along with two other men who knew what to do.

“They started CPR immediately and were about to use an automatic external defibrillator when ambulance crews arrived and used their own device to shock my heart back into action,” Ms Bayliss said.

“It’s a no-brainer to me — these guys saved my life.”

Ms Bayliss now has a defibrillator permanently installed in her body in the case of another heart episode.

In Brisbane, the city train network has no defibrillators on trains or platforms and is reliant on equipment in police outposts at three stations.

But QR chief executive Nick Easy said that would soon change.

“We are moving to make automated external defibrillators (AEDs) available, initially at 12 priority locations,” he said.