Automated external defibrillators can save the life of someone with an abnormal heart rhythm, but documents obtained by CBC News show there have been hundreds of incidents involving the device, sometimes with deadly results.
During the past five years, there have been 562 reports to Health Canada of defibrillators failing when a patient was involved.
Nine patients died when a defibrillator did not work, the documents show.
In 102 cases, the devices wouldn't power on or turned off unexpectedly.
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In Cape Breton, Tanya Lahey's 14-year-old son Kenzie needed a defibrillator when he collapsed at a Nova Scotia rink after being hit in the chest with a puck.
"It was the longest 10 to 15 minutes of my life," Lahey recalled. "We really thought Kenzie was going to die there in front of us on the ice."
The rink had a defibrillator, but the battery was dead when Kenzie needed it.
A nearby paramedic performed CPR on Kenzie until an ambulance arrived and he was saved.
In another 78 reports to the regulator, the defibrillator did not charge or deliver a shock.
Dr. Roopinder Sandhu, a cardiac electrophysiologist at the Mazankowski Alberta Heart Institute in Edmonton, analyzed the records for CBC News.
Sandhu said there is no question that defibrillators save lives, but the Health Canada documents show people need to do a better job of monitoring them.
Mandating maintenance of vital devices
"In order for it to function properly, there needs to be routine maintenance, there needs to be replacement of any damaged or expired supplies," Sandhu said. "The manufacturers should be contacted about battery life and any recommendations as to battery replacement."
Each year, up to 20,000 Canadians experience a sudden cardiac arrest.
On average, about five per cent of them survive.
Source: Health Canada
Depending on the defibrillator type, the battery and electrode pads need to be replaced every few years.
For some patients, defibrillators don't deliver a shock because it's not needed.
"Let's be clear," said CBC medical specialist Dr. Karl Kabasele. "Just because an AED doesn't deliver a shock to a given patient, it doesn't mean the machine has failed. The machine does a diagnosis and decides whether a shock is appropriate."
Health Canada, which licenses the devices, declined an interview on the number of reported failures, but said in an email: "Given the clear health risk to people who suffer cardiac arrests without immediate defibrillation, the information contained in the incident reports does not alter our assessment that the potential health benefits of the devices to people in cardiac arrest outweigh the risks.
"It's also important to keep in mind that these devices are used in life-saving circumstances. Problems may arise from the fact that they are used in urgent situations, and not necessarily by trained or prepared users."
Lahey is pushing for a national tracking system to know how often the vital portable devices at schools, arenas and workplaces are checked.
Manitoba recently passed legislation mandating fines against the people responsible for the units if they are not maintained.