From the earliest days of human history, the boundary between life and death was marked by the moment a person’s heart stopped, breathing ceased, and brain function shut down. A person became motionless, lifeless, and was deemed irreversibly dead. This is because once the heart stops beating, blood flow stops and oxygen is cut off from all the body’s organs, including the brain, and within seconds, respiration stops and brain activity comes to a halt. Since the cessation of the heart literally occurs in a “moment,” one which had been a medically irreversible point throughout history, the philosophical notion of a specific moment of “irreversible” death still pervades society today.

After the birth of intensive care medicine in the 1950s and 60s, it became increasingly possible to keep a person’s heart beating even if traumatic brain injuries had culminated in irreversible brain damage and “brain death.” This led to the recognition that people who have suffered brain injuries that permanently damage the whole brain and render it non-functional should also be able to be declared dead, even if their heart is kept beating artificially due to intensive care interventions.

In the United States, the 1981 Uniform Declaration of Death Act, which is used to declare death, states that an individual who has sustained either irreversible cessation of circulatory and respiratory functions (death by cardiorespiratory criteria) or irreversible cessation of all functions of the entire brain, including the brain stem, can be declared dead (death by brain death criteria). Today, due to the reduction in gun crimes and increased use of seatbelts in cars, fewer people suffer permanent brain damage and brain death after traumatic brain injury. Thus, while a very small minority of people are declared dead based on brain death criteria, the vast majority of the population is declared dead based on cardiorespiratory criteria—after the heart stops beating.

The Advent of Cardiopulmonary Resuscitation (CPR)

The advent of CPR in the 1960s was revolutionary, demonstrating that the heart could potentially be restarted after it had stopped. What had been a clear moment of death was shown to be potentially reversible in some people. What was once called death—the ultimate end point—was now widely called cardiac arrest, and became a starting point. From then on, it was only if someone had requested not to be resuscitated or when CPR was deemed to have failed that a person would be declared dead by “cardiopulmonary criteria.” Since the discovery of CPR, physicians have simply shifted the time before irreversible death is declared. However, biologically speaking, cardiac arrest and death by cardiopulmonary criteria are the same process, albeit marked at different points in time depending on when a declaration of death is made.

What has become increasingly clear is that the presumed irreversible loss of cardiac and respiratory function that is used for the declaration of death largely reflects the limitations of modern medicine and resuscitation techniques at any given time, rather than a verifiable point of permanent cellular and biological damage after the heart has stopped. In other words, while death is correctly based on the assumption of irreversible loss of cardiac and respiratory function, this irreversibility reflects the lack of medical alternatives when CPR fails, rather than true irreversible cellular death in the body. This distinction is very important, as when irreversible loss of function arises due to failures of CPR; consequently, if alternative treatments were available to reverse the underlying process, a person could potentially be brought back. However, when irreversible function arises due to the latter, no treatment will ever be able to reverse the process.

The introduction of CPR challenged the prevailing notion that life and death were absolute states of being: a person was either alive or dead, and that status could change in a moment. Experiences and research in the ensuing decades have shown that the boundary between life and death is a blurred line, a “gray zone” in which it can be possible to bring some patients back to life even when they have moved beyond the threshold of what has traditionally been considered death.