A medical instrument used for detecting sounds within the body, invented by French physician René Laënnec in 1816. The first stethoscopes consisted of simple tubes or cones made of paper or wood. Modern instruments consist of a bell or diaphragm made of metal or plastic that is placed on the patient's body to pick up and amplify sound and conduct it via a flexible Y-shaped rubber tube to earpieces placed in the ears of the examiner. Normal and abnormal sounds can be detected from heart, lungs, and bowels.
History
The stethoscope was invented in France in 1816 by René-Théophile-Hyacinthe Laennec.
Rappaport and Sprague designed a new stethoscope in the 1940's which became the standard by which other stethoscopes are measured. The Rappaport-Sprague was later made by Hewlett-Packard, and today there are still cardiologists who consider it to be the finest acoustic stethoscope. Several other minor refinements were made to stethoscopes until in the early 1960's Dr. Littmann, a Harvard Medical School professor, created a new stethoscope that was lighter than previous models.
Current practice
The stethoscope is used in aid of diagnosing certain diseases and conditions. The stethoscope is able to transmit certain sounds and exclude others. Before the stethoscope was invented, doctors placed their ear next to the patient's body in hopes of hearing something.
Stethoscopes are often considered as a symbol of the doctor's profession, as doctors are often seen or depicted with a stethoscope hanging around their neck.
Stethoscopes are also used by mechanics to isolate sounds of a particular moving engine part for diagnosis.
Types of stethoscopes
Acoustic and Electronic
Acoustic stethoscopes are familiar to most people, and operate on the transmission of sound from the chestpiece, via air-filled hollow tubes, to the listener's ears. If the diaphragm is placed on the patient, body sounds vibrate the diaphragm, creating acoustic pressure waves which travel up the tubing to the listener's ears. The problem with acoustic stethoscope is that the sound level is extremely low, making diagnosis difficult. Currently, a number of companies offer electronic stethoscopes, and it can be expected that within a few years, the electronic stethoscope will have eclipsed acoustic devices.
Electronic stethoscopes require conversion of acoustic sound waves to electrical signals which can then be amplified and processed for optimal listening. Unlike acoustic stethoscopes, which are all based on the same physics, transducers in electronic stethoscopes vary widely. Another method, used in Welch-Allyn's Meditron stethoscope, comprises placement of a piezoelectric crystal at the head of a metal shaft, the bottom of the shaft making contact with a diaphragm. This diaphragm responds to sound waves identically to a conventional acoustic stethoscope, with changes in an electric field replacing changes in air pressure. This preserves the sound of an acoustic stethoscope with the benefits of amplification.
More recently, ambient noise filtering has become available in electronic stethoscopes, with 3M's Littmann 3000 and Thinklabs ds32a offering methods for eliminating ambient noise.
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