This would be a handy summary to put on your GM screen about severe and permanent wounds as well:
"Omens of War
p.12+ Chapter 2 - Severe Injury Rules (Summary)
Severe injuries have a basic effect (like all criticals) and a severe effect. The basic effect is always applied while the wound is face up - just like any other critical wound. However, the wound may worsen as the character is subjected to additional abuse, ultimately bringing its severe effect into play. When the total severity of critical wounds (including Severe Injuries, and including the card in question) equals or exceeds the Severity Threshold, the severe effect is also applied. If the total severity of critical wounds is later reduced to less than the Severity Threshold, then the severe effect is once again ignored.
Healing Severe Injuries
Severe Injuries are healed just like any other critical wound, with one exception: if a character still has any non-Severe Injury critical wounds remaining, he cannot recover from a Severe Injury. In essence, Severe Injuries must be healed last.
Mortal Wounds from Hero's call are not Severe Injuries. They are regular critical wounds with a severity of 4 that must be healed before any other critical may be healed.
Some Severe Injuries may become permanent. When they first become permanent, place a tracking token on it. This means that it is permanent, but still the wound is not closed. Once it is healed, the effect is permanent (example severed leg), but the character can put the wound card aside and is no longer suffering from that critical wound."