The Stethoscope - Then & Now

By Jordie Papa

Image courtesy of torange.biz

The most recognizable medical diagnostic tool on Earth has been used for everything from listening to the rhythm of the heart, to eavesdropping on what’s been said next door.  Yet if you ask most medical professionals where the venerable stethoscope originated, they’ll be hard pressed to answer your question, let alone name the French physician who is credited as inventing the device.

Before the stethoscope, there was the ear.

Before the nineteenth century, the only way to listen to what was going on inside a patient’s chest was to apply the ear. The shortcoming of this technique meant that the resultant sound was not amplified.  As a result, it was quite possible to miss sounds that were associated with illness. It also required the physician to be in intimate contact with the patient, which could also pose a problem, particularly if the patent happened to be of the opposite sex. 

So ingrained was the sense of propriety during the 1800’s, that some physicians were reluctant to conduct a though examination.  Such was the case in 1815, when Dr. Rene Laennec found himself reluctant to perform a chest exam on a young female patient.  To avoid having to touch the patient, the physician rolled-up several sheets of paper to listen to the patient’s chest.  Not only were her heart sounds clearly audible through the tube, but he found they were amplified.  Excited at this result, he began to experiment with other materials and it wasn’t long before Laennec’s first stethoscope was invented.  (He is also credited with naming the stethoscope by combining the Greek word for chest (stethos) with skopein, which means to view.)

Image by wikimedia

Looking more like an ear trumpet used by patients who were hard of hearing, the monaural wooden device was placed on the patient’s chest, with the physician cocking his head to one side to listen to sounds emanating from the thorax.  While the use of the device was a bit more awkward than modern binaural stethoscopes, it far out performed the ear.  It wasn’t until 1851 when the first stethoscope designed for both ears was pioneered by Irish physician, Arthur Leared.

The first commercial stethoscopes came out a year or so later, after New York MD, George Cammann not only refined Dr. Leared’s binaural design, he also published an essay extolling the virtues of the new and improved device, entitled On Variations in Pitch in Percussion and Respiratory Sounds and their Application to Physical Diagnosis. (Try saying that 3 times fast.) 

While some physicians of the era speculated that using two ears as opposed to one could actually create auditory imbalances that could affect diagnosis, by the turn of the century these concerns had all but vanished. While binaural stethoscopes of the period would be easily recognized by modern healthcare professionals, they were heavier and more awkward to wield than their modern counterparts.

Stethoscope Technology of the 20^th Century

Believe it or not, the next hundred years after the introduction of the binaural stethoscope saw relatively little progress.  Other than making the instrument lighter and more flexible, modern stethoscopes don’t look all that different from those made during the 1930’s.  However, the introduction of electronic amplification and noise filtering now allow modern physicians to hear internal sounds that stethoscopes of yesteryear were incapable of producing.

Image courtesy of Melnick Medical Museum

It wasn’t until the early 1990’s that anyone really took note that stethoscope acoustics had essentially been the same since the first binaural stethoscopes had been introduced 140 years before.  That’s when Caltech grad student Clive Smith decided to do something about it.  Founding Thinklabs in 1991, the company dedicated itself to the development of electronics and signal processing for medical applications.  After reviewing all of the stethoscope literature he could lay his hands on (this was pre-Internet, after all), Smith learned that electronic stethoscopes had been around since the 1880’s, when Doctor Willem Einthoven placed a microphone in a stethoscope.  While his invention of the Electrocardiogram won him the Nobel Prize, his enhanced stethoscope wasn’t as universally adopted. 

Even in the early 1990’s, cardiologists still complained that traditional stethoscopes were poor at amplifying heart sounds.  During one of his many all-night brainstorming sessions, Smith pondered how replacing air with electrons could enhance the performance of the stethoscope.  After a number of applications were considered and rejected, Clive Smith decided to concentrate his research on the effects of replacing air pressure with an electric field.   Thus was born the Electromagnetic Diaphragm, which culminated in multiple patents being issued to Thinklabs.

Today, there are a number of manufacturers and distributors in the USA that provide healthcare professionals with stethoscopes.  Ranging in price from $60-$500, these aren’t your grandparent’s stethoscopes.  Broken down into 10 different categories, including neonatal, infant, pediatric, fetal, cardiology, veterinary, electronic, amplifying, and digitizing, modern stethoscopes are as specialized as the medical professionals who use them. 

When it comes to choosing a stethoscope that’s right for you, take it for a test drive.  Littman Stethoscopes offers the following advice when you are considering a new stethoscope:

1.      Ask colleagues if you can listen through their stethoscopes.

2.      Look at the features. See if the headsets are easy or hard to adjust.

3.      Put the diaphragm on your chest using light pressure. Hear your heartbeat? Notice how loud the sound is.

4.      Now take the new stethoscope you are considering and do the same test.  Is the sound louder? 

5.      How heavy are the two stethoscopes?  (Lighter is better)

6.      Note how the eartips cross.  (If the stethoscope isn’t symmetrical, this will cause discomfort.)

7.      How comfortable are the eartips? (Are they hard or soft?)

8.      How stiff is the tubing? (Make sure there are no bends or kinks.)  

Jordie Papa is owner of Uniform Destination with four locations in North Florida offers scrubs and medical accessories, including stethoscopes.