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Initially heart sounds were auscultated by placing the ear directly on
the chest of the patient. For the sake of convenience and propriety, Dr.
Rene Theophile Hyacinthe Laennec (1816) rolled up a sheet of paper and
placed one end over the patient's heart and the other end over his ear.
Dr. Laennec later replaced the rolled paper with a wooden tube (similar
in appearance to a candlestick) which was called "stethoscope" from the
Greek words "stethos" (chest) and "skopein" (to look at). By discovering
and perfecting the acoustic trumpet, Laennec became the father of
auscultation. The refinement of the stethoscope is an ongoing process
and is reflected by the great variety of quality stethoscopes available
today.
There were no significant developments to Laennec's device over the next
decade or so, apart from the fact that Pierre Adolph Piory, a pupil of
Laennec, refined the original device with the provision of a large flat
or concave ear piece to cover the external ear, (which exists to this
day as a Foetoscope). About one year later in 1829, Dr. Charles Williams
improved the original Laennec stethoscope by dividing the instrument into
two parts, manufacturing it from gutta percha with a joint that permitted
it to be twisted at various angles. This enabled the physician to stand
in a more comfortable position, apply less pressure to the patient's
chest, and also observe simultaneously "pulsations in the neck."
The design of stethoscopes changed little over the next 40 years or so,
apart from the development of a differential stethoscope having two
separate chestpieces, with tubing connected to each ear. Some work in
1894 by an Italian, Aurelio Bianchi, on a complex stethoscope
incorporating a water seal, (which proved impractical in a clinical
setting and was subsequently abandoned), resulted in a patent being
filed by an engineer in the USA, R.C.M. Bowles, for a simple modern
diaphragm chestpiece.
A growing acceptance of the need of both the bell and diaphragm,
led Howard Sprague to design the first combination bell and diaphragm
chestpiece in 1926, which essentially remains with us to this day,
albeit in a considerably refined form.
In the 1940's, Dr. Sprague, working with Maurice Rappaport,
scientifically investigated the physical principles of stethoscopy,
upon which much current knowledge is founded.
Again, for an extended period until 1958, few developments were made
until a new design by Dr. Aubrey Leatham, an English cardiologist,
was revealed. This stethoscope differed from earlier designs in that
not only was it a combination diaphragm and bell stethoscope, but it
incorporated a second much smaller bell inside the first. The smaller
bell was extended by a lever mechanism enabling easier and more
accurate auscultation of infants and children.
In 1961 another "electronic" stethoscope was developed by Amplivox,
taking advantage of the smaller vacuum tube technology then available.
This was intended purely as a teaching device, given its considerable
weight and size. Again, microphone and amplifier technology, did not
match the physicians' needs, and this proved to be a rudimentary device
soon abandoned in favor of conventional stethoscopes.
Perhaps the most significant milestone occurred in 1961, when Dr.
David Littmann, a cardiologist at West Roxbury VA Hospital, in
Massachusetts, designed a streamlined, lightweight stethoscope,
with a single tube binaural, which was available in both stainless
steel and light alloy. Dr. Littmann had long been aware of the
shortcomings of heavy and cumbersome stethoscopes currently available,
and of the extraneous noise generated when the two tubes of the then
existing models rubbed or snapped together. The Littmann combination
stethoscope quickly became one of the most popular models in use,
because of its light weight, flexibility and excellent acoustic
properties.
The popularity of the Littmann stethoscope came to the attention of
the 3M company and was purchased by them in 1967. The Littmann
stethoscope continued to grow in popularity, and specialized
models were added to the existing range.
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Stethoscope Basics
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Techniques: Learn how to get the best
acoustical performance from your stethoscope.
History of Stethoscopes: Learn the history
of one of the most valuable diagnostic instructions in the history
of medicine.
Stethoscope Anatomy: Dissect one of our
most popular stethoscopes and learn the significance of each piece.
Short vs. Long Tubing: Determine the
tubing length that is right for you.
Differences in Acoustics: Discover
what variables contribute to acoustical response.
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