LONDON — Leslie Burke does not want to spend the rest of his life imagining a slow, painful end. He can picture it: lying still, unable to communicate but conscious every second as his doctors let him die.

"That is, in my mind, the most inhumane way possible for someone to die," said Burke, 45, who suffers from a degenerative brain condition that in 15 to 20 years will incapacitate him.

Burke has launched a legal battle in Britain that has far-reaching medical and ethical implications, raising questions about patient autonomy, doctor responsibility and use of resources. His case, simply put, is that he demands that the state give him nutrition and water to stay alive once he is no longer able to feed himself, even if the quality of his life might seem poor to an outsider.

The lawsuit plays into the worldwide debate, especially since the Terry Schiavo case in the United States, about when life should be sustained and when it can be allowed to end.

"I think the Leslie Burke case is the most important bioethical lawsuit that I'm aware of in the world today," said Wesley J. Smith, an anti-euthanasia activist who advised Schiavo's parents before the death of the brain-damaged woman and is based at the Discovery Institute, a think tank in Seattle.

Burke went to court last year to object to guidelines issued by the General Medical Council, the body in Britain that oversees medical licensing. It says doctors may, even against a patient's expressed wishes, withhold or withdraw life-prolonging treatment if they deem a patient's condition so severe and his prognosis so poor that artificial feeding would be more of a burden than a benefit.

Trial court Justice James Munby sided with Burke, ruling that a patient, as long as he is competent to make decisions, should decide. When a patient is incompetent, life-prolonging treatment should be denied only if the treatment would be "intolerable" to the patient were he capable of exercising judgment. The judge ordered the medical council to revise its guidelines.

But the medical council appealed. During a three-day hearing last week, the two sides laid out their arguments before a panel of three judges in the Court of Appeal.

The medical council argued that the initial ruling was too broad, saying that the judgment could be interpreted to mean that patients had the right to demand treatment doctors didn't believe was in the patients' interests. Even artificial feeding can sometimes do more harm than good, the council said.

Instead of using strict "intolerability" as a test, doctors should be allowed to reach a consensus with people close to the patient if withdrawal of feeding is in a patient's interest, it argued.

Burke's lawyer said the guidelines contradict the European Convention on Human Rights, which protects a person's "right to life." He said Burke did not want doctors deciding that his life was no longer worth living.

Since the case of Tony Bland, who suffered irreparable brain damage after being crushed by a crowd in a 1989 soccer-stadium disaster, British courts have defended the right of families to withdraw artificial nutrition and hydration in some hopeless instances.

But they have stopped short of endorsing any right to assisted suicide, or euthanasia.