Lately, I’ve been dreaming about trauma. In my spare time, I’ve been doing ride-alongs with Aircare, the EMS helicopter based out of Orlando’s level 1 trauma center, just to get a taste of my former life as a paramedic. (Does it make me a bad person to wish for a critically injured patient?) You could say I've had trauma on the brain.
To me, trauma is the most exciting realm of emergency medicine. Traumatic injuries can result from a variety of scenarios, from crashes to falls to shootings and stabbings. But they all have one thing in common: physics. Let’s explore.
We’ll begin with a quick trip back in time… It’s the mid-1600s and a less-than-stellar student named Isaac Newton is attending Cambridge University in England. We’ve all heard the story: he’s reclining under an apple tree when suddenly, out of the blue, he is bonked on the head by an errant piece of fruit. The blow to his noggin results in his epiphany that gravity exists, that it can help explain the motion of planets, and that, if an object has enough mass, it can do serious damage to one’s head.
OK, I made that last bit up. In fact, the whole story is fairly bogus. Yes, young Newton supposedly observed an apple fall to the ground (no mention of head injury), which may have triggered contemplation of the moon’s orbit. However, it took him years of study, informed by the works of Descartes, Galileo and Kepler, to develop what would become some of the most important and impactful discoveries of motion and light.
So what does any of this have to do with traumatic injury? A lot, it turns out.
It wasn’t so much Newton’s theories on light and gravity that would influence trauma medicine some four hundred years later (although anyone who has taken a tumble knows the inherent drawbacks of gravity). It was his later work on motion, which he handily summarized in three laws, that would elucidate the drama of trauma and its devastating effects on the body. Since you’re probably not interested in the mathematics behind Newton’s laws and the thought of explaining quantum mechanics is enough to send me screaming, we’ll simply explore the basics of the three axioms and how they relate to the treatment of trauma patients.
Law number one: A body in motion remains in motion unless acted upon by an outside force. Say you’re driving along one night when suddenly you veer off the road and strike a tree. In compliance with Newton’s first law, if you were travelling fifty miles per hour, so were your internal organs. Your car strikes the tree, your body, if unrestrained, then strikes the steering wheel, and your internal organs slam against the confines of your body (brain against skull, heart against ribs - you get the picture). Each impact has consequences for the body’s tissues. This is why seatbelts are so important. Seatbelts provide a mechanism for keeping you from impacting the inside of the vehicle when it is brought to a sudden stop. Yes, seatbelts can do their own damage at high speeds, but I’d take a seatbelt injury over a steering wheel to the chest any day.
Law two: The force on an object is equal to its mass times its acceleration. Think about our collision—car vs. tree. The heavier the vehicle (more mass), and the faster it is moving (acceleration), the greater the impact when it strikes an object; especially if that object is also massive (say, an oak tree). Which leads us to the third law.
Law three: To every action, there is an equal and opposite reaction. Once again, in our collision we were travelling fifty miles per hour, which means that the tree we struck will push back with the equivalent force of fifty miles per hour of speed. Thus the motto, “Speed kills.” How much better off we would have been had we been putting along at a snail’s pace. High speed impacts have devastating effects on the body. The breaking of bones, the shearing of vessels, and the subsequent bleeding that results from these injuries make trauma patients some of the most complex to manage, since any - and many! - body systems can be involved.
Thanks to Newton, we can make predictions as to the types of injuries that will result from traumatic events. Whether it’s an auto accident, a shooting, or a fall, if we know the speed of the vehicle, the caliber and velocity of the bullet, or the height of the fall, we can infer the potential damage inflicted upon the body. Thus, the “mechanism of injury” is one of the fundamentals of trauma assessment and it all originates with the genius of Newton.
Could Newton have imagined the impact his work would have on trauma medicine? Perhaps… The 17th century was a period of dramatic discoveries in science and medicine. The year 1628 saw the publication of Harvey’s An Anatomical Study of the Motion of the Heart and of the Blood in Animals, which detailed his groundbreaking work on the cardiovascular system (although he scores no points for brevity of title); Frenchman Jean-Baptiste Denis and others were tinkering with blood transfusions and slowly refining their techniques - dog to human simply didn’t work. And Leeuwenhoek would perfect the microscope, under which he would discover blood cells and microorganisms (along with the creepy-crawlers inhabiting his own dental plaque). In this climate, it would seem natural for Newton to appreciate the impact (no pun intended) of his laws on medicine.
And if he actually was hit on the head with an apple, surely he could envision the carnage, had that apple instead been a cannonball.
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Here's an absolutely ridiculous video about mechanism of injury, in case you have some time to kill...