What is Mechanical Asphyxia, and How Did it Cause George Floyd's Death?
A recent autopsy revealed that Floyd died not only from the knee placed on his neck, but also from the pressure applied to his back by two other officers.
On May 25, George Floyd, a 46-year-old black man, died after a police officer held his knee on Floyd's neck for nearly nine minutes. Initially, preliminary findings from the Hennepin County Medical Examiner's office discounted asphyxiation or strangulation in Floyd's case. But now, a private autopsy shared on Monday, June 1, and performed by doctors hired by Floyd's family, has concluded that Floyd's cause of death was "mechanical asphyxia" and "the manner of death was homicide."
That same private autopsy, per The New York Times, also concluded that Floyd died not only from the knee placed on his neck by former Minneapolis police officer Derek Chauvin, but also from the pressure applied to his back by two other police officers who helped Chauvin pin him down. The independent medical examiners also added that the handcuffs used on Floyd and his positioning on the ground contributed to his death, as both instances impaired Floyd's diaphragm from functioning properly, per ABC News.
Following Floyd's death, Chauvin was arrested and later charged with second-degree murder and second-degree manslaughter. The other officers involved in Floyd's arrest and death have been fired from the Minneapolis Police Department but have not yet been charged.
“Mechanical asphyxiation” isn’t a term most people are familiar with, and it’s understandable that you might have some questions. Here’s what you need to know.
What is asphyxia, in general?
When you breathe in air through your nose and/or mouth, it enters the lungs. From there, your lungs pull out oxygen and send it through your blood vessels to your vital organs, like your brain and heart, according to the National Heart, Lung, and Blood Institute (NHLBI). “Oxygen is required for our cells to survive,” Amita Avadhani, DNP, associate professor, Advance Practice Division at the Rutgers University School of Nursing, tells Health.
Asphyxia is a condition that happens when the body is deprived of oxygen, Harold Bell, PhD, an associate professor of physiology at Central Michigan University who researches the regulation of breathing rhythm, tells Health. “Lack of oxygen to any tissue is bad, but the brain has almost zero capacity to function outside of an oxygen-based metabolism,” he says. “If it’s deprived of oxygen for any period of time, it starts to experience dysfunction.”
If you suffer from asphyxia, you’ll first experience dizziness, confusion, and disorientation, Bell says. Then, you’ll lose consciousness. “It can happen fairly quickly, within seconds to a minute, depending on how fast or severe the lack of oxygen is,” Bell says.
Asphyxia isn’t always deadly, but it can be. It can also create serious health conditions, even if someone doesn’t die from asphyxia, Mark Conroy, MD, an emergency medicine physician at The Ohio State University Wexner Medical Center, tells Health. “Any time someone loses consciousness but continues to have a lack of oxygen, that can lead to traumatic brain injury, neurocognitive dysfunction, and trouble with memory,” Conroy says. “And, if the cause of asphyxia continues, it can lead to death.”
What is mechanical asphyxia?
There are different subtypes or categories of asphyxia to help explain what, exactly, caused the asphyxia in the first place. It’s important to point out that there is no standard way of breaking down the different forms of asphyxia—something experts have argued needs to change. “The classification of asphyxia and the definitions of subtypes are far from being uniform, varying widely from one textbook to another and from one paper to the next,” says one study published in the Journal of Forensic Sciences. “Unfortunately, similar research designs can lead to totally different results depending on the definitions used. Closely comparable cases are called differently by equally competent forensic pathologists.”
That said, experts generally know what the others are talking about when they use certain terms to describe asphyxia. There is no official definition for it, but mechanical asphyxia—sometimes referred to as traumatic asphyxia—generally means there was some kind of mechanical obstruction of the airflow to the lungs, Bell says. “The most common cause of mechanical asphyxia is choking, that is, something gets stuck in the airway and blocks it,” he says. “But it also includes when someone is choked.”
Mechanical asphyxia is also used to describe “strangulation such as suicide by hanging or homicide by compressing the neck to choke the person as in the unfortunate case of Mr. Floyd,” Avadhani says. A person's airways can even be broken from too much pressure, Bell says, leading to mechanical asphyxia.
Are there other forms of asphyxia?
Yes, but again, experts stress here’s no set breakdown of the different types of asphyxia, and that there can even be overlap between different forms of asphyxia. “There’s not a lot of good literature or guidance on this,” Dr. Conroy says. In general, though, you may hear about these different types:
This is a “broad category,” Bell says. It can result from toxic substances in the body and include things like an opioid overdose (which can suppress your brain stem activity, causing you to stop breathing) and exposure to phosgene gas, a gas used in chemical warfare that inflames the lungs, he says. Carbon monoxide or exposure to cyanide can also cause this, Conroy says.
Pathological typically refers to some kind of injury or disease, like a spinal cord injury that leads to difficulty breathing or a physical problem someone is born with, Bell says. “There really are an endless number of causes that could lead to this,” he says.
This is rare, but it can include things like being exposed to low levels of oxygen at high altitudes, Bell says. “As you go up in altitude, the air becomes thinner,” he explains. That could happen in a plane if the cabin decompresses or from hiking at high elevation. “But these scenarios are very rare,” Bell says.
This describes "anything where we don’t really have a clear answer for why someone asphyxiated," Dr. Conroy says. In the case of iatrogenic asphyxia, doctors will generally know that someone developed asphyxia, but they can’t figure out how it happened. "'Iatrogenic' is a catchall term for what we don’t understand," Dr. Conroy says.
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