Does swallowing saliva mixed with blood from bleeding gums, unintentionally, especially when feeling nauseous from trying not to swallow it, invalidate a compensatory fast?

Whatever amount of blood overwhelms you and enters your throat unintentionally or swallowed by mistake does not invalidate your fast, due to the Almighty's saying: "Our Lord, do not take us to task if we forget or make a mistake," and His saying: "There is no blame upon you for that in which you have erred, but [there is blame for] what your hearts have intended." Fasting is only invalidated by intentionally swallowing blood when it was possible to spit it out.