What damage done to your body would be considered סכנת אבר, and what shabbat prohibitions can you break. This is a NON סכנת נפשות case.
My understanding from Rabbonim today is that anything that is a סכנת אבר is going to lead to surgery, which is going to lead to general anesthetic, which is סכנת נפשות. Certainly as a ספק.
Therefore, today there is no practical distinction.