There have been three 'Code Zero' situations in London in the past 48 hours, meaning there were no ambulances available to answer calls.

That means every single ambulance in the city, even those in town from the county and other nearby counties were busy. And there's no quick fix.

Scott Simpson of OPSEU Local 147 says, "In the last 10 days, we've been down to zero or one ambulance to respond in the City of London multiple times. At least once a day in the last 10 days."

The official numbers are slightly lower, but still show three incidents of where there were no available ambuilances in the entire city in the past 48 hours.

Simpson says "If you're the general public calling for an ambulance and there's nobody to repond - who are you waiting for?"

He adds there are two main factors contributing, firstly "Being stuck in the hallways at the hospital when they get overcrowded and get busy."

That's because the London Health Sciences Centre has been at capacity all week, with no beds available, and even designating a nurse to take care of people brought in via ambulances hasn't cleared the backlog.

Carol Young-Ritchie, VP of Patient-Centred Care at LHSC, says, "Sometimes a number of patients arrive in an hour, that slows down our processes. December has been a busy month for us and what we do is adjust to those volumes as they come in."

Although hospitals certainly play a role in getting ambulances back out on the street, paramedics says the problem lies primarily with staffing.

"If we had more trucks - more paramedics on the road- we wouldn't have these issues," Simpson says.

But Neal Roberts, chief of Middlesex-London EMS, disagrees, and points the finger at dispatch.

"We currently don't control our dispatch, it's controlled by the Ministry of Health."

And he says they over-prioritize, turning urgent scenarios into emergencies.

"We're going out lights and sirens 65 per cent of the time. We're only returning lights and sirens 19 per cent of the time. So obviously, there's a huge variance, which is very taxing on the system."

It's so taxing that ambulances from other counties have to be called in to fill in the most important gaps, though some remain.

Simpson says, "There was a call that waited for up to 90 minutes for somebody to respond. In our minds - in my mind - that's unacceptable. That's an EMS system that is broken."

The chief points out that 55 paramedics will be hired over the next 10 years, but that will do little to ease backlogs over the holidays closed doctors' offices mean more illnesses turn into emergencies.