I don't suppose someone better educated in these things could work out what kind of vital statistics and symptoms a person in this situation might reasonably have, which would communicate that a patient with this kind of wound was critical but increasingly stable? It would need to be the kind of data a paramedic could gather while in transit so no involved tests but certainly EKG rhythm, blood pressure, pulse-rate, general physical demeanor and the like would all be possibilities. I just need a few factors that would make an emergency medical team optimistic and some that would perhaps make them still concerned.
ETA: A little more detail for any medical-type people looking at this:
If you know my current fandom and read this carefully, you can perhaps work out a decent guess of what scene this medical situation comes from. I've been trying very hard to avoid actual spoilers, and I'm still not giving away anything too explicit. That said, this situation I'm describing is from a canonical scene from Sherlock series three, and there's some details that may place together a plausible course of events.
The pertinent details are:
1. [B] is shot and assesses his situation (possibly unreliably) to be: he was shot from the front in the chest. No exit wound. There's comparatively little blood which he takes to mean the bullet is probably acting as a stopper. He falls backward to try to keep the bullet in place and minimize blood loss. [B] calms himself down to prevent shock.
2. [A] comes into a room and sees [B] collapsed on the floor. [A] checks for breath, which he seems to hear, but on asking [B] if he can hear [A], [B] is unresponsive. [A] phones for an ambulance.
3. In the next flash, [A] and [B] are in an ambulance. [B] has an oxygen mask on and a paramedic is heard to say "We're losing him," but no indication on what the exact problem is.
4. In the next flash, [B] is in an operating theater and a heart monitor shows him flatlining. Several of the doctors have turned away from the operating table, apparently thinking it's beyond hope, but eventually [B]'s heart starts beating vaguely, then stronger. The scene closes with with [B] whispering a single (very spoilerish) word around a tube struck down his throat.
Based on this, my initial chain of events - [B] is shot but is stable enough for paramedics to be reassuring to [A] in the ambulance ride seems overly simplistic. Also, the fact that he was given both an oxygen mask and was apparently intubated at some point makes me think there are lung issues, but [B] himself thinks toward the end of moment (1) that the main danger is loss of blood due to a bullet tearing through his chest. [B]'s a scientist, not a medical doctor, and he's also just been shot so he may not actually be a reliable source, but the fact that it seems to be a stopped heart makes me suppose (in my very much amateur evaluation) that it's heart problems rather than breathing that comes closest to killing him.
So what I need help working out is,
A - is there a likely series of injuries that would result in these kinds of symptoms, and
B - what would be the physical effects of these injuries at various points, in the ambulance and in the operating room and after waking up?
Any help any one can offer on either of those points would be very much appreciated.