As my father lay in the intensive care unit after a massive heart attack -- his brain ravaged by the lack of oxygen, his chest heaving with an experimental pump, his skin slowly turning into sallow parchment -- my stepmother and I walked through the snow up Boston's Commonwealth Avenue and shared our thoughts on the unthinkable.

What were the limits of existence? At what point did life cease to exist for my father? Not on the level of breathing or bleeding but on the more fundamental plane of aliveness and personhood. As those designated to carry out his wishes, how could we draw the line between life and death on his behalf?

"If he can't play the piano, he's not going to want to live." That's where we ended up. I don't know who said it first, but I remember it was a relief that we had agreed on where to hold the line.

Like Janet Elaine Adkins, whose doctor-assisted suicide has rocked the medical community, my father loved music. Adkins, reportedly in the very early stages of Alzheimer's disease, found that her ability to play the piano had started to erode. "She would be so frustrated because she couldn't remember a song she'd known all her life," her husband said in an interview.

For my father, a lawyer, words were like granite blocks to uphold the power of reason. But music provided the wings for imagination and creativity. All his life, he scribbled tunes on sheet music and spent hours on the old Steinway in the living room.

My father, 71, had no warning. On the other hand, Adkins had planned her suicide for some time. With Alzheimer's, her brain cells would slowly degenerate. "Her mind was her life," her husband said.

In my father's case, any discussion about piano playing quickly became moot. His brain was dead, and, after a week of anguish for his family, the respirator was turned off and drugs were stopped; the twitching and grimacing ended and finally his body died, too. There was no pain or suffering for him, only for us, and his dying was relatively brief. But in the process, we joined millions of American families trapped in the prison of modern technology, where the power of medicine to treat outstrips the body's capacity to heal.

There is general agreement among doctors that aggressive treatment, such as respirators and resuscitation methods, can be withheld from dying or comatose patients if that is what they and their families desire. The Supreme Court is about to decide whether feeding tubes as well can be removed in cases with no likelihood of recovery.

Central to the dilemma of high-tech dying is the issue of quality of life. In the 1970s, health economists developed a measurement known as QALY -- Quality-Adjusted Life-Years -- that assesses the value of a medical procedure by how much it can benefit a patient. The President's Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research has endorsed quality of life as "an ethically essential concept that focuses on the good of the individual, what kind of life is possible given the person's condition and whether that condition will allow the individual to have a life that he or she views as worth living."

Yet as a report in last week's Journal of the American Medical Association makes clear, assessing the value of a life is as much the province of poets and priests as economists and mathematicians. In the rush to hold down medical costs, the QALY measure has the potential for abuse at the bedside. Most important, perceptions of well-being vary enormously. In one study, elderly outpatients with chronic diseases believed their quality of life was better than their doctors thought it was. Perhaps, for Adkins, her mind was her life; perhaps, for my father, playing the piano was the proper benchmark for his family to take in their stunned helplessness. But that is a narrow view.

My brother knows best. He and my father were cross-country skiing that cold February day by the river when the heart attack struck and our father collapsed. Amidst the scream of ambulance sirens and the crush of the emergency team, my brother stepped back. Someone in the crowd took his hand and guided him to Marlborough Street, where he sat on the stoop of my parents' apartment building.

Born brain-damaged, my brother is autistic and retarded. It has been eight years since our father's death. Brad, 33, loves when it snows and the white flecks float to the ground. We reminisce a lot about what fun it was to ski with father on fresh powder snow. He has a job in a medical device company and lives in a house run by Goodwill Industries. And, of course, he can't play the piano at all.