A few months ago, I was walking home from the year-end party commemorating the end of the first year of medical school. As I walked along the river at midnight, I saw a small shape dart through the trees and disappear into the dark. The brief glimpse of a winged silhouette immediately conjured images from a favorite childhood novel “Silverwing” by Kenneth Oppel. Bats!
You should know that I had a strong obsession with animal documentaries as a kid and planned for making said documentaries to be my backup career if AI ever replaces all of us in medicine. As I thought back to the many facts I learned about bats, I suddenly found myself drawing a connection to a research project I had just started. I must have looked silly, laughing alone at night on the sidewalk, but I could not stop myself from seeing bats as flying Point of Care Ultrasounds (POCUS) devices. I raced home and, instead of getting some much needed sleep, fired up my computer for a quick history lesson.
Bat Myths
Bats are the only mammals on earth that are capable of sustained flight. This, shockingly, is not one of the cool facts for which bats are commonly known. Instead, people imagine them as blood-sucking winged rodents. Thankfully, this is not the case for most bats you will encounter, and vampire bats generally don’t find humans to be attractive feeding grounds in any case. Most species “simply” hunt tiny bugs, essentially invisible in the night sky. This stellar hunting ability is all thanks to their capacity to interpret sound waves bouncing off objects in their surroundings.
In 300 BC, Aristotle wrote “as the eyes of bats are to the light of day, so is the intellect of our soul to the objects which in their nature are most evident of all”. Unfortunately, by trying to create a philosophical quote, he sparked a misleading assertion. First, bats can in fact see reasonably well with their eyes even in daylight. Second, you cannot think about bat sight through the limitations of human vision.
The idea that bats are blind has persisted even to this day with the phrase “blind as a bat”. However, the 18th century Italian physiologist Lazzaro Spallanzani challenged this assertion with a simple experiment. Covering the eyes of bats, he found that they navigated their environment exceptionally well while blind. However, he was surprised to find that after plugging their ears, the bats suddenly struggled to avoid obstacles during flight. It took another 150 years for researchers to coin the term “echolocation” to describe the use of high frequency clicks to “see”.
A Brief History of POCUS
Like many things in nature, echolocation became an inspiration for human invention and innovation. In 1906 Lewis Nixon, a naval architect, invented the first passive sonar system to aid in detecting icebergs. World War I then spurred rapid development of an active sonar system as a necessity for identifying enemy submarines. Sound waves were even adapted into a tool for identifying flaws in metal. Research boomed in the area.
However, it wasn’t until 1942 that sonograms were used for medical purposes, when Karl Dussik attempted to locate brain tumors through the skull. The world of cardiology was then shocked in 1953 when Inge Elder performed the first echocardiogram, while 1956 saw Ian Donald successfully
introduce the first ultrasound devices to the obstetrics clinic. Ultrasound was ready for the main stage!
As ultrasound technology improved, physicians and scientists toyed with the idea of bringing an ultrasound to the pocket of every doctor. The 1990’s showed that POCUS could be a real possibility. Today, POCUS continues to rapidly advance. There is a big push to advance POCUS adoption by increasing portability through connection with smartphones and improving affordability.
In Praise of Bats
Not all animals have evolved to see in the dark, but humans have learned to do so even deep inside the human body through our brilliant ability to develop new tools. There is no doubt about the value of enabling rapid bedside visualization of hearts, fluids, vessels, babies, and more! As a community, we must continue the push to get a POCUS device into every clinician’s office and integrate POCUS training into medical education. After all, seeing is believing, and that may be truer in medicine than in many other disciplines. Whether you are a junior trainee or seasoned practitioner, the ability to see your diagnosis is incredibly valuable for increasing confidence in your assessment. Equally important is that POCUS can vastly improve patient comprehension, a critical predictor of whether they will comply with a treatment plan.
While little remains to learn from bats with respect to seeing inside of the body, POCUS is built on millennia of evolution and centuries of discoveries. It is easy to forget how extraordinary the tools we use in clinic every day are. So, the next time you pick up that transducer, pause for a moment and marvel at the power that small device holds. You could even say a little thank you for the bats that made it all possible. Or don’t, but don’t come running to me if its vampire bat friends come knocking.