The use of a feeding tube for Pope John Paul II (search), struggling to recover from throat surgery, illustrates a key point of Roman Catholic policy he himself has proclaimed: It is morally necessary to give patients food and water, no matter their condition.

As Parkinson's disease (search) and other ailments have left him increasingly frail, John Paul has been emphasizing that the chronically ill, "prisoners of their condition ... retain their human dignity in all its fullness."

The Vatican has repeated that principle recently in comments concerning Terri Schiavo (search), the severely brain-damaged American woman whose feeding tube was removed earlielp him breathe, John Paul has become a picture of suffering. When he appeared at his apartment window Wednesday to bless pilgrims in St. Peter's Square, he managed to utter only a rasp.

Later that day, the Vatican announced the pope had been fitted with a feeding tube in his nose to help boost his nutritional intake.

Under John Paul, Vatican teaching on the final stages of life includes a firm rejection of euthanasia, insistence on treatments that help people bear ailments with dignity and encouragement of research to enhance and prolong life.

A 1980 Vatican document makes the distinction between "proportionate" and "disproportionate" means of prolonging life. While it gives room for refusal of some forms of aggressive medical intervention for terminally ill patients, it insists that "normal care" must not be interrupted.

John Paul set down exactly what that meant in a speech last year to an international conference on treatments for patients in a so-called persistent vegetative state.

"I should like particularly to underline how the administration of water and food, even when provided by artificial means, always represents a natural means of preserving life, not a medical act. Its use, furthermore, should be considered, in principle, ordinary and proportionate, and as such morally obligatory."

John Paul's 26-year papacy has been marked by its call to value the aged and to respect the sick, subjects the pope has turned to as he battles Parkinson's disease and crippling knee and hip ailments.

In the Schiavo case, the Vatican newspaper L'Osservatore Romano said recently that removing the feeding tube was tantamount to capital punishment.

"But Terri has committed no crimes, if not that of being `useless' to the eyes of a society incapable of appreciating and defending the gift of life," it said.

The Rev. Thomas Williams, a Rome-based theologian, said there are parallels with John Paul's case, based on the church teaching that such feeding is required. "In that sense, there is a great similarity," he said.

But he pointed out that the pope is fully conscious and running the church. Court-appointed doctors have determined that Schiavo was in a persistent vegetative state with no hope of recovery.

The parents of Schiavo, who was raised in the Roman Catholic church, argue that she could get better and that she would never have wanted to be cut off from food and water.

In an intertwining of the cases, her parents have even cited John Paul — now with a feeding tube of his own — as saying people in vegetative states have a right to nutrition and hydration.

Feeding tubes are common in patients requiring supplemental nutrition. A "nasogastric tube," which John Paul has, is threaded down the nose and throat into the stomach. Liquid food is then fed through it. While uncomfortable, no sedation or surgery is required.

Schiavo, on the other hand, had a tube that was inserted directly into her stomach. Outside doctors say that may become necessary for John Paul if the nasogastric tube is not sufficient in improving his nutrition.

While the pope is still able to eat on his own and is fully conscious, the insertion of any feeding tube raises the question of what to do if he were to lose consciousness and be kept alive by the tube alone.

It is not clear who would be empowered to make medical decisions for an unconscious pope. The pope has no close relatives, but the Vatican has officially declined to comment whether John Paul has left written instructions.