Can a Medpatch alone, without a Medical Kit, be used to Treat Deadly Wounds by a character with the Medical Expert feat?
Yes, per the Feat description:
You can use the Medicine skill in conjunction with a medpatch or sprayflesh to treat deadly wounds as a full action.
it can be done. This is a case of specific trumps general.
However, since the Medical Expert feat does not reference DCs, the
description does not includes DCs or the ability to treat deadly wounds, and the Medicine
skill description categorizes DCs as based upon equipment, any DC at this time will be subjected to DM fiat since RAW is silent (nothing on the
errata pages as of yet).
Approximating DC for use.
- Medpatch : DC N/A
- Sprayflesh : DC 25
- Basic Medkit : DC 25
- Advanced Medkit : DC 20
- Medical Lab : DC 20
The range of Treat Deadly wounds ranges from DC20(advanced medkits/medlabs) to DC25(everything else).
This puts a Medpatch at the high end, or DC25 for treat deadly wounds.
Given that the 2 separate items(Sprayflesh and Medpatch) cover the full range of the medicine skill, and are explicitly called out by the feat, it makes sense for those two to share a DC when used in the special circumstances outlined.
How about Sprayflesh?
If you succeed at a DC 25 Medicine check, the next time such a creature rests for 10 minutes and spends a Resolve Point to regain Stamina Points, it can instead gain the benefit of your Medicine check to treat deadly wounds
As the above shows, it has a DC25 medicine check for treating deadly wounds, even if it is in a roundabout way.
Since the feat Medical Expert says:
When used in this way, the medpatch or sprayflesh does not perform any of its normal functions
Then it is likely intended to just be DC25 medicine check while using Sprayflesh in conjunction with the Medical Expert feats to Treat Deadly Wounds