Under the Medical Priority Dispatch System, or MPDS, ambulances will be dispatched based on answers to detailed questions, and according to five colour-based levels based on the “acuity” of the situation.

Top-priority calls are now marked as “purple,” which indicates there are immediate life-threatening conditions, where time is critical. This accounts for about two per cent of calls.

Next on the priority list is “red,” which means emergent and potentially life-threatening, representing about 38 per cent of calls. Time is sensitive in these cases.

“Orange” is urgent and potentially life-threatening. Time may be a factor. This accounts for 17 per cent of calls.

“Yellow” is non-urgent, but potentially serious. Time is sensitive. It’s about 19 per cent of calls.

“Green” is non-urgent and not serious, with no immediate threat to life, and it may be deferred without detriment to the patient’s outcome. This is about 24 per cent of calls.