The Biggest Questions: What is death?
To do so, though, we need to reconsider how we conceive of and approach life and death. Rather than thinking of death as an event from which one cannot recover, Parnia says, we should instead view it as a transient process of oxygen deprivation that has the potential to become irreversible if enough time passes or medical interventions fail. If we adopt this mindset about death, Parnia says, “then suddenly, everyone will say, ‘Let’s treat it.’”
Moving goalposts
Legal and biological definitions of death typically refer to the “irreversible cessation” of life-sustaining processes supported by the heart, lungs, and brain. The heart is the most common point of failure, and for the vast majority of human history, when it stopped there was generally no coming back.
That changed around 1960, with the invention of CPR. Until then, resuming a stalled heartbeat had largely been considered the stuff of miracles; now, it was within the grasp of modern medicine. CPR forced the first major rethink of death as a concept. “Cardiac arrest” entered the lexicon, creating a clear semantic separation between the temporary loss of heart function and the permanent cessation of life.
Around the same time, the advent of positive-pressure mechanical ventilators, which work by delivering breaths of air to the lungs, began allowing people who incurred catastrophic brain injury—for example, from a shot to the head, a massive stroke, or a car accident—to continue breathing. In autopsies after these patients died, however, researchers discovered that in some cases their brains had been so severely damaged that the tissue had begun to liquefy. In such cases, ventilators had essentially created “a beating-heart cadaver,” says Christof Koch, a neuroscientist at the Allen Institute in Seattle.
These observations led to the concept of brain death and ushered in medical, ethical, and legal debate about the ability to declare such patients dead before their heart stops beating. Many countries did eventually adopt some form of this new definition. Whether we talk about brain death or biological death, though, the scientific intricacies behind these processes are far from established. “The more we characterize the dying brain, the more we have questions,” says Charlotte Martial, a neuroscientist at the University of Liège in Belgium. “It’s a very, very complex phenomenon.”
Brains on the brink
Traditionally, doctors have thought that the brain begins incurring damage minutes after it’s deprived of oxygen. While that’s the conventional wisdom, says Jimo Borjigin, a neuroscientist at the University of Michigan, “you have to wonder, why would our brain be built in such a fragile manner?”
