Every country in the world with the technology - and willingness - to keep such patients alive has had its Terri Schiavo. Almost every one has dealt differently with the dilemmas the drama raised.
From the Netherlands, where euthanasia and assisted suicides are legal and common, to India, where no doctor is allowed to deny lifesaving treatment to any patient, no matter how hopeless, governments are struggling to draft ethical and practical laws governing so-called mercy killing.
In the meantime, say doctors and activists on both sides of the debate, doctors are turning off thousands of life-support machines every day behind curtains of ambiguity and confusion, lacking clear legal guidelines.
Even in Europe, where debate has led to more legislation than anywhere else, "active euthanasia ... is regularly practiced even in countries where it is prohibited," a recent Council of Europe report found. "Criminal convictions and administrative and professional sanc- tions are, on the other hand, extremely rare."
For most people in the world, living in poor countries with few sophisticated life-support machines, the debate swirling in the United States around Ms. Schiavo's case is almost unimaginable.
The dilemma facing Schiavo's family members "is not a major issue at all" for Indians, says Roopinder Singh, a commentator for The Tribune newspaper in Chandigargh. The huge costs involved in keeping someone alive for 15 years would be "killing for the family," he adds.
Similarly, at the world's largest hospital, in the black South African township of Soweto, AIDS is a much more pressing problem. Nearly 2,000 people - half of them HIV positive - check into Chris Hani-Baragwanath each day.
"A lot of resources would be going to maintain" a patient like Schiavo, "and you might say they could be used elsewhere," explains Natalya Dinat, a specialist at the sprawling complex. Philosophical debates about life and death are a luxury, she says, and "you only have these luxuries where death is a rare thing."
But traditional African values, which emphasize family and community needs over individual rights, color attitudes as much as the shortage of money.
Once, argues Stella Mhango of the Khara Heritage Institute in Pretoria, that would mean "the whole community would come together" to try to save someone like Schiavo. Today, suggests Dr. Dinat, that communal ethic, and AIDS patients' fear of becoming a burden, could explain the recent 15-fold increase in suicides in South Africa.
For many outside the US, the very public twists and turns of Schiavo's case through the courts and Congress are hard to fathom.
Brazilians, for example, who rarely resolve their problems through the judiciary, tend not to feel that such personal issues are a matter for courts to decide.
"This is a question for the family," says Irene Henriquez, a Sao Paulo housewife. Nor can courts intervene in such cases in France, where "our logic is less judicial than in the English-speaking world," says Xavier Mirabel, who heads the Association for the Right to Life, based in Paris.
Cases like Schiavo's do not often come before the courts in Australia either. Most patients' relatives accept a doctor's decision that further treatment is pointless. But when judges have become involved, they have sent contradictory signals.
Last year, doctors at St. George's Hospital in Sydney decided to switch off the life-support system of a 75-year-old man in a coma. His distraught relatives took the matter to the New South Wales Supreme Court, which upheld the doctors' view.
Four years earlier, however, a court had ruled in favor of a woman trying to stop doctors removing life support from her brother, who was in a heroin-induced coma.
Recent guidelines advising New South Wales doctors on end-of-life care are designed to minimize conflicts with family members, but "they don't explain the key principle of what is appropriate and what is not appropriate" medical treatment, worries Bernadette Tobin, director of Sydney's Plunkett Center for Ethics.
In India, all treatment is deemed appropriate. Doctors there are legally forbidden to deny any treatment that might keep someone alive. The law, however, holds little sway over reality, says Chandigargh lawyer Manmohan Lal Sarin, whose father was attached to a respirator 12 years ago against his will.
Mr. Sarin was wealthy enough to keep his father in such care. But few other Indians are in that position. "When someone is brought to the hospital, they gauge whether you can pay," he says. "If not, they'll just say 'go home, there is nothing more we can do.' "
In most Muslim countries, euthanasia is abhorrent. But a number of modern Islamic scholars, perceiving the feeding tube as a form of useless treatment, would probably decide Terri Schiavo's case in favor of her husband.
"If the patient is on life support, it may be permissible, with due consideration and care, to decide to switch off the life-support machine and let nature take its own time," Dr. Muzzamil Siddiqi, former president of the Islamic Society of North America, wrote recently.
The controversial and popular Egyptian scholar Sheikh Yusuf al-Qaradawi, who has backed the use of suicide bombers against civilian targets in Israel, recently issued a fatwa, or religious ruling, equating euthanasia with murder, but allowing the withholding of treatment that is deemed useless.
In Russia, euthanasia is illegal, period. But courts have been sympathetic to people charged with helping others die. Two women in the southern city of Rostov-on-Don were found guilty last year of murdering Natalya Barranikova - even though the court accepted that the paralyzed victim had asked them to kill her - because the law is clear. But the defendants were given unexpectedly light sentences.
In Britain, too, laws against euthanasia and assisted suicides have been weakened by court rulings. In a case matching Schiavo's, doctors decided in 1993 to remove the feeding tube that had kept Tony Bland alive, since he had fallen into a persistent vegetative state following a soccer-stadium disaster.
Mr. Bland's parents took the case all the way to Britain's highest court, the House of Lords, which sided with the doctors.
A brain-damaged baby, Charlotte Wyatt, who needs an oxygen mask to breathe, is the current subject of a legal tussle after a judge ruled that her quality of life was so poor that doctors had the right not to resuscitate her. Her family wants her to live.
It was a similarly high-profile case, involving a young man left paraplegic, mute, and blind by a car accident and who begged to be allowed to die, which led the French parliament to pass a law last November clarifying doctors' responsibilities in such circumstances.
Due to come into effect later this year, the law limits "unreasonable persistence" in treating the terminally ill, and specifies that "when medical acts appear useless, disproportionate, or serve no other purpose than the artificial support of life, they can be suspended or not undertaken."
The law has been welcomed, with some reservations, by activists on both sides of the euthanasia debate, though it is ambiguous about doctors' right to give potentially fatal doses of painkillers. High doses are permitted to ease discomfort even if the doctor suspects they might kill the patient as a secondary effect, but not if they are intentionally deadly.
Stopping short of legalizing euthanasia, the law "does not go far enough," says Danielle Metro, an official at the Association for the Right to Die in Dignity, based in Paris, "but it does protect doctors better" against lawsuits by outraged relatives.
"Doctors have a duty to switch off machines in some circumstances; it would be ethically scandalous to impose them," says Dr. Mirabel, a devout Roman Catholic, who runs a website advising families on end-of-life issues. "If they couldn't turn them off, we would all die hooked up to a bank of machines, and that is not dignified."
Mirabel is unhappy, however, that the French law specifies feeding tubes as the sort of treatment that can legally be withdrawn. "Respirators can honestly be seen as unreasonable treatment, but feeding is not the same," he argues.
That is the view espoused in Spanish legislation passed three years ago, under which Schiavo's doctors would not be allowed to stop feeding her artificially unless she had personally left written instructions to the contrary.
The Spanish law resulted from the drama surrounding Ramon Sampedro, paralyzed from the neck down by an accident, whose story was told in the film "The Sea Inside," which won an Oscar last month for Best Foreign Film.
He pleaded for someone to be allowed to help him die, and eventually found someone who agreed to administer a fatal dose of potassium cyanide.
Such an act would still be illegal in Spain, but the law does allow doctors to "limit, suspend, or not initiate treatment" in certain circumstances, even if doing so will cause the patient's death.
Spanish public opinion is strongly in favor of legalizing euthanasia, as are 60 percent of Spanish doctors, an unusually high proportion.
"The fundamental problem is that the medical professions are not united on this," says Derek Humphry, a lifelong campaigner for euthanasia and assisted suicide, whose bestselling book, "Final Exit," explains methods of suicide.
"The only reason there is sensible legislation in the Netherlands and Belgium is because the medical profession has been supportive," he adds.
In Belgium, euthanasia has been legal since 2002, as it has been in the Netherlands, along with physician-assisted suicide. The two countries report about 2,500 cases a year. In Switzerland, assisted suicide has not been a crime since 1946.
Opinion polls in Europe suggest that some 80 percent of voters would approve such legislation in their countries. The Catholic church, however, remains strongly opposed to the idea, though some bishops have condoned the suspension of aggressive treatment and the administration of potentially fatal painkillers in the interest of relieving a patient's suffering.
"In the end," says. Mirabel, "aggressive therapy and euthanasia both have the same intention. They stem from a desire to master the end of life, and a refusal to accept something that is beyond us."
• Contributors: Dan Murphy in Cairo, Mark Rice-Oxley in London; Lisa Abend in Madrid; Abraham McLaughlin in Johannesburg, South Africa; Janaki Kremmer in Sydney, Australia; Andrew Downie in Sao Paulo, Brazil; Vir Singh in New Delhi; and Fred Weir in Moscow.