Viewpoint: The curious history of the first stethoscope

Physicians as early as Hippocrates were accustomed to listening to heart and lung sounds by placing their ears directly on the chest of the patient, a process called "immediate" or direct auscultation. To avoid direct contact with a patient's skin, physicians would interpose a handkerchief between their ears and the patient's chest. Immediate auscultation continued into the early 19th century, until French physician René Théophile-Hyacinthe Laennec invented the first stethoscope.

One day in 1816, Laennec observed children playing with long hollow sticks. The young scientists were intrigued by how a pin used to scratch the stick at one end would transmit and amplify the sound to the other. On a subsequent patient visit, Laennec needed to listen to the chest of an obese young woman. Rather than place his ear on the patient's bosom, he recalled his observations of the children playing and instead he rolled several sheets of paper into a cylinder and used this to auscultate his patient's chest. He was amazed by what he heard:

I rolled a quire of paper into a kind of cylinder and applied one end of it to the region of the heart and the other to my ear, and was not a little surprised and pleased to find that I could thereby perceive the action of the heart in a manner much more clear and distinct than I had ever been able to do by the immediate application of my ear.
-René Laennec, De l'Auscultation Médiate

Laennec was a keen observer and used his invention to expand the science of medical auscultation by correlating his observations with autopsy findings. He was the first to describe rales, rhonchi, crepitance, and egophany. His invention was favorably reviewed in the New England Journal of Medicine only 2 years after its introduction, and eventually most physicians came to accept Laennec's invention. After publication of his observations in 1819, he became quite famous and ultimately became chair of the College of France in 1822 and a professor of medicine in 1823. It was Laennec's nephew who used the stethoscope to diagnosis his uncle with tuberculosis, which caused Laennec's death in 1826 at the age of 45, just 10 years after his discovery.

Over the years, innovative physician scientists further refined Laennec's original stethoscope.

In 1852, George Cammann produced the first binaural (2-earpiece) stethoscope, which became the standard device used by physicians for close to a half-century. Cammann's stethoscope was made with an ebony chest piece and flexible tubing made of spirals of wire covered with layers of silk dipped in gum elastic. It had ivory ear tips. In 1894, Robert Bowles introduced the first diaphragm-based stethoscope, and in the 1940s, Drs Sprague and Rappaport introduced the 2-sided stethoscope chest piece with a diaphragm and bell to improve auscultation of sounds of differing frequencies. While the Sprague-Rappaport design was very popular, most physicians disliked the interference produced by its 2-tube design. In the 1960s, David Littmann, a cardiologist and professor at Harvard Medical School, redesigned the stethoscope with a single tube that had 2 internal channels and further refined the acoustics of the device.

In the 1990s, several companies produced "electronic" stethoscopes that had the ability to filter out ambient noise and amplify auscultated heart and lung sounds, and over the past 2 decades these have become increasingly popular among medical providers. Last year 3M-Littmann released a new stethoscope with Bluetooth capability that transmits auscultated heart sounds to a computer for software analysis, beginning a new era where physicians can use computer-assisted auscultation and digital stethoscopy to improve patient care.

It all began with a French physician who learned the benefit of child's play.

Old concepts, new technology