“Code Blue!” was first announced in 1964 over the intercom of Bethany Medical Center in Kansas City. It meant that a patient’s heart had stopped beating and it brought Dr. Robert Potter running, pushing a cart that his father, a sheet-metal fabricator, had cobbled together. The cart contained a bed board, used to quickly move a patient, tubes for insertion into a patient’s windpipe, a bag used to force air into the lungs, and defibrillator paddles, together weighing about a hundred pounds, that were electrified and applied to a patient’s chest to restart their heart.

Experiments using electric shock to restart the heart had been conducted by Russian and other European doctors since the mid 1950s. Potter’s innovation was refining the process and making it portable. Defibrillation quickly spread to hospitals across the US. Soon 911 lines and ambulance services were able to deliver cardiopulmonary resuscitation (CPR, rhythmic external pressure to the heart combined with the use of portable defibrillators), to any person anywhere in the country. While doctors quickly adopted defibrillation, which saves lives about forty percent of the time, the public saw CPR as nothing short of a miracle. Even today, TV shows depict the procedure as life-saving seventy-five percent of the time.

The earliest sheet-metal carts, writes William H. Colby in Unplugged: Reclaiming Our Right to Die in America, “were unstable... and it wasn’t uncommon to round a corner in a hurry, and have the whole contraption tip over—hence the name ‘crash cart.’” “Code Blue” referred to either the color that Potter’s father had painted the carts or the color that a patient turned when their heart stopped circulating oxygen. Despite the clown car scramble, Dr. Potter’s “Code Blue” could save lives—it could reclaim a person from the clutches of death.

For the entire course of human existence, death had meant one thing: the almost simultaneous end of heartbeat, breathing and brain function. Victorian-era doctors held a mirror in front of a patient’s mouth and nose, looking for steam. Into the 1960s, the ultimate test, often reluctantly performed by the newest intern on the hospital ward, was to touch a patient’s eyeball with a piece of cotton. The corner of a hospital gown was likely the closest thing at hand. If the patient didn’t blink, the ghost had been given up.

For centuries, we understood that ghost to reside in the red, rhythmic organ in our chests. Ancient Egyptians removed all organs but the heart before mummification, believing it was needed for success in the afterlife. In the 1600s, the “hollow muscle” was the residence of the soul, equated in occult literature to the sun, it’s microcosmic life-source akin to the sun’s macrocosmic light. In the 1970s, Dr. Potter’s new ability to artificially preserve the heart meant that defibrillator and respirator use became widespread, and brain function, not heartbeat, became the determining factor for who’s dead—or alive.

As early as 1968, the medical community could see what was coming: the Harvard Ad Hoc Committee to Examine the Definition of Brain Death determined that the death of the brain should be considered the death of the human. The report sparked a dispute primarily because the committee was seen as reserving the decision of death for themselves and because they cited two pragmatic reasons for their conclusion: pain suffered on the patient, their family and the medical system by prolonged coma (nailing two sacrosanct issues in one blow, “noble” suffering and “demoralizing” money); and the need to protect organ harvesting from controversy.

The Florida Supreme Court case of Terri Schiavo is just one of many that has since tested the legal definition of death. After Schiavo collapsed in her home in 1990, she was found by her husband, Michael, who called the paramedics. He didn’t know how long she had been unconscious and it took emergency medical technicians seven tries to restart her heart. Because her body was young and strong, she didn’t require a respirator once at the hospital. Michael consented to a feeding tube as Terri was unconscious and unable to eat on her own. Eight years later, with no sign of improvement, he requested that the tube be removed and that Terri be allowed to die. He loved her, but he felt that the Terri he knew was no longer there. Ultimately, the Florida courts upheld his request, but not before a lengthy national publicity scrum that engaged the conservative right-to-life faction, the Catholic Church, state and federal lawyers and politicians, and eventually President George W. Bush.

Was Terri alive? This was not a question the courts wished to answer. Instead they relied on legal precedent that stated a person, or their medical proxy, had the right to deny any medical treatment they chose, even if it meant certain death. (A similar tack had been taken by the courts two decades before regarding abortion. Is a fetus alive? Instead the Supreme Court decided Roe v. Wade on the basis of privacy: that a woman should make her own medical decisions, up until viability, or the fetus’s ability to live outside the womb.)

Terri Schiavo’s family, who opposed the removal of her feeding tube, are vocal representatives of a “pro-life” faction who advocate for an end to the “killing” of “severely disabled” patients. In short, they are what Tom L. Beauchamp and Robert Veatch, in the introduction to their 1996 book Ethical Issues in Death and Dying, call the “small but significant minority” who will “continue to hold that an individual with a beating heart is still alive even if that heart is maintained mechanically and there is no brain function.” Beauchamp and Veatch write that those engaged in the debate over the definition of death, “recognize this choice as a moral, religious, or philosophical one, not one that can be made solely on the basis of scientific evidence.”

Any time we talk about the definition of death, of course, we’re also talking about the definition of life. What, then does alive mean? Biological life, whether maintained by machines or not? The ability to blink or swallow? To recognize your mother when she walks into a room? To remember your own name, hold a job, or contribute to society? To the families of those on life support, these questions are vital. Their answers inform the decision of when to remove respirators and defibrillators.

Another Florida case, one that came to the courts six years before Schiavo’s, also addressed the definition of death. Theresa Ann Pearson was born with a condition called anencephaly, in which a functioning brain stem allows the lungs and heart to work, but the rest of the brain, which regulates those functions, is missing. When Baby Theresa’s parents were informed of her condition, they decided to carry the pregnancy to term so that her organs could be donated to other infants in need. Baby Theresa was delivered via caesarean section, but when her parents asked that she be declared dead for the purpose of organ harvesting, their health care providers refused. A Florida statute determined that the child was a “live birth” and not a candidate for organ donation. By the time she died nine days later, her organs were no longer suitable for donation.

The 1970s Dead Donor Rule (DDR) states that “organ donation must not kill the donor; thus, the donor must first be declared dead.” In a 2013 article for the New England Journal of Medicine, James L. Bernat argues that the DDR is “not a law but an informal, succinct standard.”

When it comes to organs, however, the fresher the better. The increased need for organs has pressured doctors to reconsider the DDR. Doctors Truog, Miller and Halpern write, also in the New England Journal of Medicine this year, that interpretation of the DDR has expanded to include patients who have suffered “an irreversible loss of circulatory function,” otherwise known as heart failure:

This requirement has led to rules permitting organ procurement after the patient has been pulseless for at least two minutes. Yet for many such patients, circulatory function is not yet irreversibly lost within this timeframe—cardiopulmonary resuscitation could restore it. So a compromise has been reached whereby organ procurement may begin before the loss of circulation is known to be irreversible, provided that clinicians wait long enough to have confidence that the heart will not restart on its own…

How long is long enough? Doctors have advocated that, just as patients or their families can decide when to remove life support (as Michael Schiavo decided for his wife), so too they should be able to decide when their life ends and organ harvesting can begin. After fifty years with no clear answer, dead can mean what you want it to.

Just as morality and values change over time, so too do medical ethics. Dr. Potter’s crash cart has wheeled us, careening around blind corners, into a world where death is increasingly a decision, made by patients and their families. It’s anyone’s guess how these decisions will continue to shape our lives.