HALIFAX -- A senior medical official says Nova Scotia -- where nine of its 38 hospital emergency rooms shut at least temporarily last week because of staffing shortages -- may ultimately need fewer ERs than it has.

David Petrie, senior medical director of the emergency program of care for the Nova Scotia Health Authority, said such changes won't be universally popular. But he said the discussion is necessary as the health system grapples with overall doctor shortages and a shifting landscape in emergency medicine.

Petrie said there are a number of factors contributing to ongoing temporary closures -- especially over the summer months -- that require remedies that are "difficult and complex."

"What's the right number? We're not sure," Petrie said in an interview.

"Certainly we don't think it's 36 or 38 -- it's probably less, but that doesn't mean a hospital will disappear."

He said key to any future decisions will be finding the right balance, so as not to create more physician coverage problems.

"I'm not naive to the fact that there will be political ramifications to this," he said.

"We see our role in the emergency program of care to make recommendations to senior leadership and we have to weigh in other factors that aren't necessarily medical in this decision making."

Petrie's point was evident in June when Premier Stephen McNeil was heckled and booed as he announced the pending closure of two Cape Breton hospitals, New Waterford Consolidated and Northside General, including their ERs.

As part of the announcement McNeil said emergency departments at two nearby hospitals -- the Cape Breton Regional Hospital and the Glace Bay Hospital -- would be expanded.

The most recent accountability report on emergency room closures, released last December, highlighted an increase in temporary closures of about 460 hours in fiscal 2016-17 -- the fourth such increase in as many years.

Emergency departments schedule 313,538 open hours each year, with 25,124.5 hours of closure recorded in the 2016-17 report.

Petrie said the final numbers aren't ready yet for fiscal 2017-18, although there has been a "slight" downward trend in the last couple of years. He said in 2015-16, 98.3 per cent of emergency room hours were covered, while 96.7 were covered off in 2016-17.

He said the vast majority of closures are in small rural emergency departments.

"My sense is it's probably a little worse this summer," Petrie said.

Over the last week, as many as eight emergency departments experienced some temporary closures and that number increased to nine over the just-concluded long weekend. Communities affected included Sheet Harbour, Lunenburg, Shelburne, New Waterford and Pugwash, among others.

Petrie said vacation scheduling adds to the problem during the summer months, although he said it's necessary to allow health professionals the time to refresh themselves in order to avoid burnout and more long-term problems for the system.

He said planning is done at the local level, although only so much can be done when unforeseen problems such as sudden illness or accidents kick in.

Petrie said the ongoing doctor shortage plays a part, as well as a specific shortage of doctors trained in emergency medicine.

He pointed to a 2016 report by the Collaborative Working Group on the Future of Emergency Medicine in Canada.

That report found an estimated shortfall of 478 emergency physicians nationally, and projected that without an expansion of emergency medicine residency that number would rise to 1,071 by 2020 and 1,518 by 2025.

Petrie said the province is working to address its own shortfall by increasing the number of emergency medicine seats, while it also tries to boost overall recruitment efforts in the face of looming doctor retirements.

He said boosting the number of qualified doctors is key because emergency medicine has changed over the last 20 years, requiring greater competency.

"Primary care physicians coming out of their two-year residencies aren't feeling necessarily as comfortable doing emergency medicine any more, so that's part of the issue."

Petrie said emergency room closures can also be addressed through more robust locum programs that would see doctors being given the opportunity to fill in at more than one location in the province.

Support must also be improved for primary care physicians working in smaller centres through telemedicine, maintenance of competency programs, and real-time decision making support, he said.

They are solutions that can make a difference, Petrie said, adding that "optimistically" the system could get to a point within a year or 18 months where emergency department closures would be rare.

"It may get a little worse before it gets better, but it certainly can get better and should get better over time," he said.