Paramedics and the University of Ottawa are crediting quick-thinking bystanders and a public defibrillator for helping a young man who suffered a cardiac arrest on Tuesday afternoon.

The 23-year-old was studying on the third floor of the university's Montpetit Hall at about 2:15 p.m. when his heart stopped.

Other students, staff and campus safety officers rushed to help.

A student nearby used an emergency phone to call security, who called 911. Over the phone, an emergency dispatcher gave CPR instructions to the group.

A public defibrillator unit was then found in a nearby lab.

'He's very, very lucky,' paramedics say

"They administered one shock and then one of our paramedics arrived on scene and administered another. They continued CPR and after a third shock was delivered he had a spontaneous return of pulse and was breathing on his own," said paramedic superintendent Stephanie Logan.

"The students reacted very quickly," she said. "He's very, very lucky that they were so quick to respond and we are very hopeful that he is going to pull through."

The man was taken to hospital in critical condition.

"I think it's really neat there was no hesitation, that they saw someone in need," said student Geoff Winchester. "It could have been a stranger or could have been a friend, but they did not hesitate."

Logan said this latest episode underscores the value of defibrillators in public areas. Hundreds of the units have been put up throughout Ottawa. Logan said 11 people have survived medical emergencies after public defibrillators were used.

A university spokesperson said Tuesday that the school is proud of everyone who helped.