The EMD process is set up for multi-agency (tiered) response, but not all jurisdictions respond as such. The response levels can also be broken down further as to an ambulance responding P-1 and first response responding P-2 or vise versa.
Alpha: BLS Call Priority 2
Bravo: BLS Call Priority 1
Charlie: ALS Call Priority 1
Delta: ALS Call Priority 1, with cardiac or respiratory history or questionable life status.
Echo: ALS Call Priority 1 Immediate Life Threat; Cardiac, Respiratory Arrest, etc. In the Pro-QA/EMD Process as soon as the dispatcher reaches the question concerning life status, if the dispatcher determines that the patient is in an arrest state the Pro-QA/EMD process pauses and resources are automatically dispatched.
(Not all jurisdictions use the Echo Determinate, they still just dispatch the call as a Delta)
Omega: No response required.
Again these are recommendations and some agencies respond as THEY see fit, not according to the determination that has been given by the dispatcher.
Some agencies dispatch calls as either P1 or P2, or P1 ALS, P1 BLS, P2 BLS etc. or may even break it down to the exact “card” and symptom/history, such as 6-Delta-1 (this is just an example I am not at work so I may not get the symptom/history exact) but the 6 represents the Respiratory Distress Card, Delta Response, 1 being the symptom/history such as cardiac history which would automatically raise the call to a Delta Response.
Again, I have tried to explain it the best I can without having the Pro-QA/EMD right in front of me. We have been using the Pro-QA/EMD program for about 10 years.