The first stethoscope, invented by René Laennec, consisted of several pieces of thick paper rolled up to form a cylinder. His later designs were composed of wood and demonstrated greater audio fidelity. Even so, it wasn’t until 1830 that the device was adopted by the medical community. Since then, a number of innovators have improved upon Laennec’s initial design. Chief among these was Charles James Blasius Williams, who in 1843 developed a stethoscope that featured a trumpet instead of a wooden cylinder. The trumped fit more snugly against the chest, and it allowed sound to be channeled and concentrated. Blasius’s design also featured a removable earpiece, which meant that several doctors could share the same device.
Then, in 1851, Arthur Leared created the first binaural stethoscope. This device sent sound to both ears in two separate channels. The innovation made it easier for doctors to detect and interpret faint heart sounds. In 1852, George Cammann made a few tweaks to the design, which rendered the device cheaper to produce. Cammann took the modified stethoscope to market soon after.
By 1940, Hewlett Packard was mass producing the stethoscope as it is recognized today. This stethoscope consisted of a heavy metal chestpiece and twin latex tubes. The Rappaport-Sprague stethoscope design, as it was known, changed hands many times hence, and it was finally purchased by Philips Medical Systems, which sold it for $300.
By the 1960s, many medical professionals were seeking a lighter, longer version of the stethoscope. Additionally, some patients exhibited allergic reactions to the latex stethoscope tubes. Dr. David Littmann of Harvard Medical School tackled the problem by creating a stethoscope with longer, hypoallergenic tubes and a revolutionary tunable diaphragm. Littmann’s stethoscope was the lightest yet, and its diaphragm saved doctors time by allowing them to listen to both high frequency and low frequency sounds without having to switch from the diaphragm to the bell. To switch from one frequency range to another, doctors had only to vary the amount of pressure they applied to the skin. Littman’s device was purchased by tech giant 3M, and the company has continued to improve on the basic design ever since.
Paying homage to Littman’s legacy, modern stethoscopes are lightweight and composed of skin-friendly materials. Although innovations in the ultrasound space may soon produce an affordable hand-held ultrasound imager, the stethoscope is slated to remain an important diagnostic tool. Inventors are extending the life of the nearly-200-year-old device by integrating it into smartphones and giving it the ability to transmit data to remote servers via Bluetooth.
For instance, the StethoCloud, invented by Australian medical student Hon Weng Chong, is a system that consists of an analog stethoscope fitted with a sensitive microphone and a smartphone app that uploads heart sounds to the cloud. Doctors can use the device to keep tabs on a patient’s heart health over time, as well as compare a patient’s heart sounds to those from a diseased heart.
Although these innovations will carry the stethoscope into the new millennium, it was Dr. David Littmann that modernized the device, allowing it to detect even the faintest heart abnormalities. His innovation has saved millions of lives since its introduction in the mid 1960s.