An Ottawa doctor and an OC Transpo supervisor are being credited for helping save the life of a man who went into cardiac arrest Thursday morning on a city bus.

The 73-year-old man's bus was pulling into Hurdman station at around 11 a.m. Thursday when he suddenly collapsed, the Ottawa Paramedic Service said in a media release.

Dr. Nadya Ben Fadel, a neonatologist who works with babies in the intensive care unit at the Children's Hospital of Eastern Ontario, was among the passengers on board.

She told CBC News that she was about to disembark when she heard someone asking if another passenger was OK. She then saw the man, who appeared to be passed out.

Ben Fadel said the man's arms were shaking, his complexion was very pale, and he was having difficulty breathing.

"The instinct of being a physician just rushed in my blood," said Ben Fadel.

Ben Fadel said she asked the driver to call paramedics, and someone helped her get the man to the floor.

'Am I doing the right thing?'

As Ben Fadel began performing CPR, the driver alerted his supervisor, who happened to be just behind his bus.

"I'm a neonatologist, so we do CPR on babies every single day. It's what we do," said Ben Fadel. "But [I haven't] done it on an adult since medical school."

Ben Fadel said she'd never done chest compressions in public, and that many of the passengers were watching closely.

"I was questioning myself, 'Am I doing the right thing? Am I doing the right thing?' But the instinct that you just want to save that guy's life kept getting into my mind," said Ben Fadel.

The OC Transpo supervisor, who the paramedic service identified as Derek Fuller, rushed on board with a defibrillator from his vehicle and delivered a shock to the man's heart, said the paramedic service.

Paramedics then arrived and delivered a further three shocks, along with drugs to restart the man's heart. The man was taken to hospital, where he was moving and attempting to breathe on his own.

Defibrillators on buses?

B​en Fadel's presence on the bus was fortuitous, especially since — as she told CBC News — she was only taking transit because her husband had the family car and her son had called from school, asking her to bring him a pair of shoes.

"Obviously we're very thankful to the bus operator, the supervisor and [Ben Fadel], who really stepped up to provide this emergency aid," said Coun. Stephen Blais, chair of the city's transit committee.

People might be surprised to know that OC Transpo's command centre received some 800 medical calls in 2016, Blais said, although not all were for reasons as serious as cardiac arrest.

OC Transpo's supervisors, and OC Transpo's special constables all receive enhanced training for CPR and using defibrillators, said Blais.

Buses are not equipped with defibrillators, although Blais said that would be a "worthwhile discussion" for city officials to have.