If you know the person's wishes it is easier to make a decision.
Will further invasive treatment improve the quality of life or just the lifespan. Doctors will take that into consideration, but family members often insist on treatment, no matter what.
I have an advance medical directive in place which states I don't want measures taken to lengthen my life if there is no prospect of improvement. I don't want to be kept alive with no quality of life,
My family all know this and will respect my wishes.
It was drawn up by my solicitor but has no standing as a legal document but gives doctors an insight into the person's thoughts when they were lucid.
Think of the person and how they would feel. Don't be selfish in keeping them alive, using invasive treatment, if they won't make a meaningful recovery.
It is an onerous decision and I wish you the strength and understanding to make it. Discuss with doctors as soon as you feel able. Be kind to yourself and the patient.