With the end of a brutal heat wave that is being blamed for the deaths of 54 people, many of them elderly men and women who died alone in sweltering apartments, Quebec public-health authorities are turning to trying to find solutions to prevent such tragedies in the future.

They will zero in on each death to try to determine how the lives of people at risk can be spared as heat spells become more frequent.

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“Despite what we put in place in the last four, five days, some of the most vulnerable people are not being reached, and that is the central focus of the work we have to do,” said David Kaiser, a physician with Montreal’s health department.

The largest loss of lives happened in Montreal, where 28 died and many others were left reeling during the week of scorching weather. Calls for ambulance services shot up 30 per cent as paramedics treated people for ailments ranging from exhaustion to breathing difficulties to confusion. Often, medics entered apartments that felt like ovens.

“There was no air. It was suffocating,” said Stefan Overhoff, an operational chief with the Urgences Santé ambulance service who worked all week. “Think of temperatures 43 C, 45 C. You open a window and nothing happens.”

He said Friday that many calls were to people in upper floors of buildings where hot air became trapped. “Some people don’t have the means to get a good fan or air conditioner.”

According to figures released Friday, 40 per cent of the deaths in Montreal were women, all of them 60 or more years of age.

Could air-conditioning habits have played a role in Quebec’s death toll? Ontario is not releasing figures on fatalities related to this week’s heat, which also rolled over parts of that province. However, Ontario residents can more readily rely on air conditioners to survive extreme temperatures. Only 53 per cent of households in Quebec have air conditioning, compared with 83 per cent in Ontario and 57 per cent nationwide, according to 2015 figures from Statistics Canada.

Physicians say those most sensitive to extreme heat are the elderly, young children, pregnant women and people with chronic diseases.

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“But those who live on low incomes – those who don’t have access to air conditioning, pools or cool spaces – are most vulnerable particularly when a heat wave is prolonged as it has been this week,” says Jean Zigby, a Montreal physician and past president of the Canadian Association of Physicians for the Environment.

The group cited a report showing Montreal can expect more heat waves as a result of climate change. Before 2005, Montreal had an average eight days a year with temperatures hotter than 30 C. By 2050, the number is forecast to jump to 50 days a year.

One of the biggest factors that can determine life or death in situations such as heat waves is whether individuals have access to a support system of friends or family, said David Wachsmuth, Canada Research Chair in urban governance at McGill University in Montreal.

“There is a really large social component to this,” Mr. Wachsmuth said. “The quality of their social networks is a gigantic factor in predicting who is going to come out okay.”

Rather than leaving it up to chance, he said it’s up to cities to create programs that can target people who live alone, have underlying health problems or are otherwise at risk during extreme heat events.

Urban centres face unique challenges during heat waves because they become “heat islands” – meaning they get hotter than rural areas. A number of factors, including reduced green space and the fact concrete absorbs the sun’s energy, can make cities a few degrees hotter than outlying areas.

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The temperature in Montreal this week climbed into the mid 30s, but drenching humidity made it feel as hot as in the mid 40s. The city got a reprieve from the intense heat Friday as daytime temperatures dipped below 20 C.

With a report from Carly Weeks