As far as I know, the ECP mod have something added to the game so when you are shot, a new option comes up, 'first aid', on the action menu. If you don't do this soon, you will die of blood loss. First aid doesn't heal you completely, but it stops you dying long enough to get to a medic.
Medics still magically heal you completely, but if this game was realistic, when you get shot in the leg you would lie there with a medic next to you until a chopper evac came along, then you would be ferried out of the warzone into a hospital for 4-6 months.
Not very fun.