Asphyxia by any other name is just as deadly
Understanding the sequelae of traumatic asphyxia, strangulation and positional asphyxia
Scrolling through the social media commentary in the aftermath of George Floyd’s death and the riots and protests that arose from it, I noticed several people posting screenshots and quotes of the medical examiner’s preliminary findings in George Floyd’s autopsy, particularly this passage:
The Hennepin County Medical Examiner (ME) conducted Mr. Floyd’s autopsy on May 26, 2020. The full report of the ME is pending but the ME has made the following preliminary findings. The autopsy revealed no physical findings that support a diagnosis of traumatic asphyxia or strangulation. Mr. Floyd had underlying health conditions including coronary artery disease and hypertensive heart disease. The combined effects of Mr. Floyd being restrained by the police, his underlying health conditions and any potential intoxicants in his system likely contributed to his death.”
If we’re going to quote medical jargon without context, let’s also include the very next paragraph in the probable cause affidavit for Derek Chauvin’s arrest and charge of third-degree murder:
The defendant had his knee on Mr. Floyd’s neck for 8 minutes and 46 seconds in total. Two minutes and 53 seconds of this was after Mr. Floyd was non-responsive. Police are trained that this type of restraint with a subject in a prone position is inherently dangerous.”
It occurs to me that a brief primer on the differences between positional asphyxia and traumatic asyphxia and strangulation is warranted. Much like the difference between an abdominal aortic aneurysm and an aortic dissection, even medical professionals mistakenly use the terms interchangeably. While we’re out there representing the EMS perspective on social media, our explanations can go a long way toward refuting the fake news our layperson friends lack the medical education to spot.
Respiratory distress, impairment
First, let’s dispel the myth that says, “If you can say ‘I can’t breathe,’ then that is proof that you can.”
Being able to phonate merely means that your airway is open; there is no mechanical or anatomical obstruction of your vocal cords. There may very well be a significant impairment in respiratory efficiency, and medical professionals can gather further history and perform a physical examination to determine the extent of that impairment, if any. By not refuting that myth whenever we hear it, we encourage laypeople and police officers to believe it when they lack the education and training to rule out a serious condition.
Now, on to the differences between traumatic asphyxia, strangulation and positional asphyxia.
Traumatic asphyxia is a medical term used to describe sudden traumatic compression of the chest cavity, resulting in engorgement and rupture of blood vessels in the shoulders, neck, face and head. It’s a specific sequelae of a dramatic and sudden increase in intrathoracic pressure; an inadvertent Valsalva maneuver combined with crush injury. Physical findings include jugular venous distention, bulging eyeballs, and engorgement of tongue and lips, all resulting from the tremendous spike in venous back-pressure. Myocardial contusion, pulmonary contusion, and bilateral pneumothorax are often present as well – the infamous paper bag syndrome.
Think frontal impact car crash or building collapse. Traumatic asphyxia is a cardiovascular phenomenon, not a respiratory one.
Positional asphyxia, on the other hand, is every bit an impairment of respiration and ventilation. Typically, it occurs in prone positioning of large or obese patients, particularly those with a protuberant abdomen. Crossed-arm restraint in large people can also interfere with chest excursion and cause a similar effect. Tidal volume is decreased due to limited chest expansion, and a host of sequelae follow; respiratory acidosis, atelectasis, pulmonary edema, organ and tissue ischemia, and so on. Any pre-existing cardiovascular or respiratory condition that can be exacerbated by hypoxia can and will be exacerbated by positional asphyxia.
Add an actively struggling, combative patient to the mix – like, for example, an excited delirium patient on sympathomimetic drugs – and you can add metabolic acidosis, hyperkalemia, and rhabdomyolysis to the list of harmful sequelae.
The end result is an express train to death. It is the medical professional’s job to divert that train. When you’re restraining a combative patient, the goal is to end the fight.
Successful physical restraint does not end the fight, it just transfers the fight to patient versus restraints.
What the patient needs is chemical restraint and sedation, and proper positioning to maintain effective respirations. Semi-Fowler’s combined with limb restraint accomplishes that; prone restraint does just the opposite.
Hanging, ligature strangulation and manual strangulation
Strangulation results from compression of the structures in the neck, typically the larynx, trachea and great vessels. Strangulation is broadly divided into three self-explanatory categories: hanging, ligature strangulation and manual strangulation.
Strangling need not result in death. An example are the chokeholds used by MMA fighters or police restraining violent suspects. It should be noted that chokeholds applied by police are now considered deadly force options, in the same category as firing a service weapon in defense of life. No ethical cop promotes the use of chokeholds when the patient is not resisting or their resistance does not pose an immediate and deadly threat to the officer.
Typically, a chokehold compresses the external carotid arteries and jugular veins, resulting in cerebral ischemia and rapid loss of consciousness. The carotid sinus reflex may be stimulated, resulting in vasoconstriction, bradycardia and hypotension; a twin in mechanism to the mammalian diving reflex.
Ligature and manual strangulation, however, result in compression, edema, and even crushing of the larynx and trachea; a degree of force roughly six times that required to cause vascular strangulation. It takes a strong person to manually strangle someone without a ligature.
More importantly, these are the things evident on an autopsy. Hanging often results in all of the vascular signs of traumatic asphyxia – above the ligature, at least – accompanied by edema and crush injury to the larynx and trachea, and fracture of the C1-C2 vertebrae – the classic hangman’s fracture. Fracture of the hyoid bone is also considered a hallmark physical finding in ligature strangulation or hanging, and may also be present in manual strangulation.
These findings weren’t apparent in George Floyd’s autopsy because that wasn’t the force applied. He didn’t asphyxiate due to a car steering wheel at 60 mph; or a house caving in on him; or someone strangling him with hands, garotte or a noose.
He asphyxiated because a grown man knelt on his neck for eight and a half minutes, despite him pleading that he couldn’t breathe.