In the Deathwatch manual pg. 102 under the Medicae skill it says
"First Aid may only be applied to each wound once and is a full round action by you and your patient."
I took this to mean that is a Space Marine is shot twice he can be healed twice. This makes sense to me. For each patch wound, the Space Marine would feel a little better. However the errata states
"The First Aid use of the Medicae Skill can be used to treat any number of untreated injuries with a single Medicae Test. If successful, the Medicae Test removes damage as detailed above.Once the Medicae Test is performed, the injuries are treated (for better or worse) and cannot be treated with another First Aid Test. They may be treated with an Extended Care Test.”
This leads me to believe that you can only use the Medicae skill once and you've treated all injuries currently on that person.
Any clarification?