I am in the process of going through all the medical missions with my suggestions for changes such as vehicle requirements and CC chance. This includes missions added before I became CA.
Cardiac arrest does not have a CC percentage assigned which is why it won't generate.
Once the change was made from HEMS requirement to CC chance required any medical missions following this were added with a CC chance and the missions before were missed out.
In terms of building collapse and firearms attack, I have not been consulted about PT codes or CC chances for these missions (and others alike) and these have more than likely just been filled in by the DEVs.
Now that I have finished the Coastguard content my attention is back towards the medical side.