We can legitimately have recourse to experimental treatments if nothing else has worked.We have the right to refuse extraordinary measures and treatments that would just prolong the dying process. Food and water are the ordinary means of survival even when given via a tube and called nutrition and hydration. We have the right to refuse burdensome treatment, especially if such treatment is i) expensive; or ii) causing distress. We can even refuse to take medication for something such as pneumonia in such circumstances.It is morally acceptable to switch off a machine that is keeping a person alive artificially, if there is no chance of recovery.
If they lose their mental capacity to make judgments, a family member can make the decision, which is what Michael Schiavo did. He claimed, without conclusive evidence, that Terri would have wanted to die, he did not take any account of the wishes of Terri’s family, or her religious beliefs and the teachings of her Church on the matter, and he used doctors who supported his wishes and rejected having Terri examined by other specialists.
The Church recognises that death has occurred when someone is no longer breathing, has no circulation, and the heart is no longer beating.
When it comes to a determination of ‘brain death,’ everything becomes ambiguous. There is
no global consensus on the diagnostic criteria" and there are still “unresolved issues worldwide”.
Dr. Paul Byrne, president of the Catholic Medical Association, said,
“Brain death” is not death. Brain death is not based on data that would be considered valid for any other scientific purpose."
See more here
life.org.nz/euthanasiakeyissuesbraindeath.htm