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The stethoscope is an acoustic
medical Medicine is the science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity, awareness, or understanding of someone or something, such as facts ( descriptive knowledge), skills (proced ...

medical
device for
auscultation :''For the ancient monasterial worker, see Auscultare'' Auscultation (based on the Latin verb ''auscultare'' "to listen") is listening to the internal sounds of the body, usually using a stethoscope The stethoscope is an acoustic medical ...

auscultation
, or listening to internal sounds of an animal or human body. It typically has a small disc-shaped resonator that is placed against the skin, and one or two tubes connected to two earpieces. A stethoscope can be used to listen to the sounds made by the
heart The heart is a muscular MUSCULAR (DS-200B), located in the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use ...
, lungs or
intestines The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system The human digestive system consists of the gastrointestinal tract The gastrointestinal tract, (GI tract, GIT, d ...
, as well as blood flow in
arteries An artery (plural arteries) () is a blood vessel that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pulmonary arteries, pulmonary ...

arteries
and
vein Veins are blood vessels The blood vessels are the components of the circulatory system The circulatory system, also called the cardiovascular system or the vascular system, is an organ system An organ system is a biological system A b ...

vein
s. In combination with a manual
sphygmomanometer A sphygmomanometer ( ), also known as a blood pressure monitor, or blood pressure gauge, is a device used to measure blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics ...

sphygmomanometer
, it is commonly used when measuring
blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics, a force is an influence that can change the motion (physics), motion of an Physical object, object. A force can cause an object with mas ...

blood pressure
. Less commonly, "mechanic's stethoscopes", equipped with rod shaped chestpieces, are used to listen to internal sounds made by machines (for example, sounds and vibrations emitted by worn ball bearings), such as diagnosing a malfunctioning automobile engine by listening to the sounds of its internal parts. Stethoscopes can also be used to check scientific vacuum chambers for leaks and for various other small-scale acoustic monitoring tasks. A stethoscope that intensifies
auscultatory
auscultatory
sounds is called a phonendoscope.


History

The stethoscope was invented in
France France (), officially the French Republic (french: link=no, République française), is a transcontinental country This is a list of countries located on more than one continent A continent is one of several large landmasses ...

France
in 1816 by
René Laennec René-Théophile-Hyacinthe Laennec (; 17 February 1781 – 13 August 1826) was a French physician A physician (American English), medical practitioner (English in the Commonwealth of Nations, Commonwealth English), medical doctor, or simply ...
at the Necker-Enfants Malades Hospital in
Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, most populous city of France, with an estimated population of 2,175,601 residents , in an area of more than . Since the 17th century, Paris ha ...

Paris
.'Laennec, R. T. H.; Forbes, John, Sir,
A Treatise on the Diseases of the Chest and on Mediate Auscultation
' (1835). New York : Samuel Wood & Sons; Philadelphia : Desilver, Thomas & Co. .
It consisted of a wooden tube and was
monaural Monaural or monophonic sound reproduction (often shortened to mono) is sound intended to be heard as if it were emanating from one position. This contrasts with stereophonic sound File:Carsoundstereoshift.png, Time difference in a stereoph ...

monaural
. Laennec invented the stethoscope because he was not comfortable placing his ear directly onto a woman's chest to listen to her heart. He observed that a rolled piece of paper, placed between the individual's chest and his ear, could amplify heart sounds without requiring physical contact. Laennec's device was similar to the common
ear trumpet Ear trumpets are tubular or funnel-shaped devices which collect sound In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior throug ...

ear trumpet
, a historical form of hearing aid; indeed, his invention was almost indistinguishable in structure and function from the trumpet, which was commonly called a "microphone". Laennec called his device the "stethoscope" ('' stetho-'' + '' -scope'', "chest scope"), and he called its use " mediate auscultation", because it was
auscultation :''For the ancient monasterial worker, see Auscultare'' Auscultation (based on the Latin verb ''auscultare'' "to listen") is listening to the internal sounds of the body, usually using a stethoscope The stethoscope is an acoustic medical ...

auscultation
with a tool intermediate between the individual's body and the physician's ear. (Today the word ''auscultation'' denotes all such listening, mediate or not.) The first flexible stethoscope of any sort may have been a binaural instrument with articulated joints not very clearly described in 1829. In 1840,
Golding Bird Golding Bird (9 December 1814 – 27 October 1854) was a British medical doctor A physician (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the ...

Golding Bird
described a stethoscope he had been using with a flexible tube. Bird was the first to publish a description of such a stethoscope, but he noted in his paper the prior existence of an earlier design (which he thought was of little utility) which he described as the snake ear trumpet. Bird's stethoscope had a single earpiece. In 1851, Irish physician Arthur Leared invented a binaural stethoscope, and in 1852, George Philip Cammann perfected the design of the stethoscope instrument (that used both ears) for commercial production, which has become the standard ever since. Cammann also wrote a major treatise on diagnosis by auscultation, which the refined binaural stethoscope made possible. By 1873, there were descriptions of a differential stethoscope that could connect to slightly different locations to create a slight stereo effect, though this did not become a standard tool in clinical practice. Somerville Scott Alison described his invention of the stethophone at the Royal Society in 1858; the stethophone had two separate bells, allowing the user to hear and compare sounds derived from two discrete locations. This was used to do definitive studies on binaural hearing and
auditory processing The auditory cortex is the part of the temporal lobe that processes auditory information in humans and many other vertebrates. It is a part of the auditory system, performing basic and higher functions in hearing, such as possible relations to ...
that advanced knowledge of
sound localization Sound localization is a listener's ability to identify the location or origin of a detected sound in direction and distance. The sound localization mechanisms of the mammalian auditory system have been extensively studied. The auditory system us ...
and eventually lead to an understanding of
binaural fusion Binaural fusion or binaural integration is a cognitive process that involves the combination of different auditory system, auditory information presented Sound localization, binaurally, or to each ear. In humans, this process is essential in underst ...
. The medical historian
Jacalyn Duffin Jacalyn M. Duffin (born 1950) is a Canadian medical historian and hematology, hematologist. She held the Hannah Chair, History of Medicine at Queen's University at Kingston, Queen's University from 1988 until 2017. Formerly, she was President of ...
has argued that the invention of the stethoscope marked a major step in the redefinition of disease from being a bundle of symptoms, to the current sense of a disease as a problem with an anatomical system even if there are no observable symptoms. This re-conceptualization occurred in part, Duffin argues, because prior to stethoscopes, there were no non-lethal instruments for exploring internal anatomy. Rappaport and Sprague designed a new stethoscope in the 1940s, which became the standard by which other stethoscopes are measured, consisting of two sides, one of which is used for the respiratory system, the other for the cardiovascular system. The Rappaport-Sprague was later made by
Hewlett-Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California Palo Alto (; Spanish language, Spanish for "tall stick" ...

Hewlett-Packard
. HP's medical products division was spun off as part of Agilent Technologies, Inc., where it became Agilent Healthcare. Agilent Healthcare was purchased by
Philips Koninklijke Philips N.V. (in Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () *Dutch language , spoken in Belgium (also referred as ''flemish'') Dutch may also refer t ...

Philips
which became Philips Medical Systems, before the walnut-boxed, $300, original Rappaport-Sprague stethoscope was finally abandoned ca. 2004, along with Philips' brand (manufactured by Andromed, of Montreal, Canada) electronic stethoscope model. The Rappaport-Sprague model stethoscope was heavy and short () with an antiquated appearance recognizable by their two large independent latex rubber tubes connecting an exposed leaf-spring-joined pair of opposing F-shaped chrome-plated brass binaural ear tubes with a dual-head chest piece. Several other minor refinements were made to stethoscopes until, in the early 1960s,
David Littmann David Littmann, M.D., (July 28, 1906 – January 1, 1981) was an American cardiologist born in Chelsea Massachusetts (born to Ukrainian immigrants from Novogrod Wolyn aka Zwill Ukraine (formally the Russian Empire), Issac Litman and Sadie Zewat ...
, a
Harvard Medical School Harvard Medical School (HMS) is the graduate medical school A medical school is a tertiary education Tertiary education, also referred to as third-level, third-stage or post-secondary education, is the education Education is the ...
professor, created a new stethoscope that was lighter than previous models and had improved acoustics. In the late 1970s, 3M-Littmann introduced the tunable diaphragm: a very hard (G-10) glass-epoxy resin diaphragm member with an overmolded silicone flexible acoustic surround which permitted increased excursion of the diaphragm member in a Z-axis with respect to the plane of the sound collecting area. The left shift to a lower resonant frequency increases the volume of some low frequency sounds due to the longer waves propagated by the increased excursion of the hard diaphragm member suspended in the concentric accountic surround. Conversely, restricting excursion of the diaphragm by pressing the stethoscope diaphragm surface firmly against the anatomical area overlying the physiological sounds of interest, the acoustic surround could also be used to dampen excursion of the diaphragm in response to "z"-axis pressure against a concentric fret. This raises the frequency bias by shortening the wavelength to auscultate a higher range of physiological sounds. In 1999, Richard Deslauriers patented the first external noise reducing stethoscope, the DRG Puretone. It featured two parallel lumens containing two steel coils which dissipated infiltrating noise as inaudible heat energy. The steel coil "insulation" added .30 lb to each stethoscope. In 2005, DRG's diagnostics division was acquired by TRIMLINE Medical Products.


Current practice

Stethoscopes are a symbol of healthcare professionals. Healthcare providers are often seen or depicted wearing a stethoscope around the neck. A 2012 research paper claimed that the stethoscope, when compared to other medical equipment, had the highest positive impact on the perceived trustworthiness of the practitioner seen with it. Prevailing opinions on the utility of the stethoscope in current clinical practice vary depending on the medical specialty. Studies have shown that auscultation skill (i.e., the ability to make a diagnosis based on what is heard through a stethoscope) has been in decline for some time, such that some medical educators are working to re-establish it. In general practice, traditional blood pressure measurement using a mechanical
sphygmomanometer A sphygmomanometer ( ), also known as a blood pressure monitor, or blood pressure gauge, is a device used to measure blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics ...

sphygmomanometer
with inflatable cuff and stethoscope is gradually being replaced with automated blood pressure monitors.


Types


Acoustic

Acoustic stethoscopes operate on the transmission of sound from the chest piece, via air-filled hollow tubes, to the listener's ears. The chestpiece usually consists of two sides that can be placed against the patient for sensing sound: a diaphragm (plastic disc) or bell (hollow cup). 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. If the bell is placed on the patient, the vibrations of the skin directly produce acoustic pressure waves traveling up to the listener's ears. The bell transmits low frequency sounds, while the diaphragm transmits higher frequency sounds. To deliver the acoustic energy primarily to either the bell or diaphragm, the tube connecting into the chamber between bell and diaphragm is open on only one side and can rotate. The opening is visible when connected into the bell. Rotating the tube 180 degrees in the head connects it to the diaphragm. This two-sided stethoscope was invented by Rappaport and Sprague in the early part of the 20th century. One problem with acoustic stethoscopes was that the sound level was extremely low. This problem was surmounted in 1999 with the invention of the stratified continuous (inner) lumen, and the kinetic acoustic mechanism in 2002.


Electronic

An electronic stethoscope (or stethophone) overcomes the low sound levels by electronically amplifying body sounds. However, amplification of stethoscope contact artifacts, and component cutoffs (frequency response thresholds of electronic stethoscope microphones, pre-amps, amps, and speakers) limit electronically amplified stethoscopes' overall utility by amplifying mid-range sounds, while simultaneously attenuating high- and low- frequency range sounds. Currently, a number of companies offer electronic stethoscopes. 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. The simplest and least effective method of sound detection is achieved by placing a microphone in the chestpiece. This method suffers from ambient noise interference and has fallen out of favor. 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. 3M also uses a piezo-electric crystal placed within foam behind a thick rubber-like diaphragm. The Thinklabs' Rhythm 32 uses an
electromagnetic diaphragm An electromagnetic diaphragm is a form of capacitive sensor used on an electronic stethoscope. The diaphragm is coated with a conductive material. A conductive plate is positioned behind and parallel to the diaphragm, so that the two conductive e ...
with a conductive inner surface to form a capacitive sensor. This diaphragm responds to sound waves, with changes in an electric field replacing changes in air pressure. The Eko Core enables wireless transmission of heart sounds to a smartphone or tablet. Because the sounds are transmitted electronically, an electronic stethoscope can be a wireless device, can be a recording device, and can provide noise reduction, signal enhancement, and both visual and audio output. Around 2001, Stethographics introduced PC-based software which enabled a phonocardiograph, graphic representation of cardiologic and pulmonologic sounds to be generated, and interpreted according to related algorithms. All of these features are helpful for purposes of telemedicine (remote diagnosis) and teaching. Electronic stethoscopes are also used with Computer-aided Auscultation, computer-aided auscultation programs to analyze the recorded heart sounds pathological or innocent heart murmurs.


Recording

Some electronic stethoscopes feature direct audio output that can be used with an external recording device, such as a notebook computer, laptop or MP3 recorder. The same connection can be used to listen to the previously recorded
auscultation :''For the ancient monasterial worker, see Auscultare'' Auscultation (based on the Latin verb ''auscultare'' "to listen") is listening to the internal sounds of the body, usually using a stethoscope The stethoscope is an acoustic medical ...

auscultation
through the stethoscope headphones, allowing for more detailed study for general research as well as evaluation and consultation regarding a particular patient's condition and telemedicine, or remote diagnosis. There are some smartphone apps that can use the phone as a stethoscope. At least one uses the phone's own microphone to amplify sound, produce a visualization, and e-mail the results. These apps may be used for training purposes or as novelties, but have not yet gained acceptance for professional medical use. The first stethoscope that could work with a smartphone application was introduced in 2015


Fetal

A ''fetal stethoscope'' or ''fetoscope'' is an acoustic stethoscope shaped like a listening trumpet. It is placed against the abdomen of a pregnancy, pregnant woman to listen to the heart sounds of the fetus. The fetal stethoscope is also known as a Pinard horn after French obstetrician Adolphe Pinard (1844–1934).


Doppler

A Doppler stethoscope is an electronic device that measures the Doppler effect of ultrasound waves reflected from organs within the body. Motion is detected by the change in frequency, due to the Doppler effect, of the reflected waves. Hence the Doppler stethoscope is particularly suited to deal with moving objects such as a beating heart. It was recently demonstrated that continuous Doppler enables the auscultation of valvular movements and blood flow sounds that are undetected during cardiac examination with a stethoscope in adults. The Doppler auscultation presented a sensitivity of 84% for the detection of aortic regurgitations while classic stethoscope auscultation presented a sensitivity of 58%. Moreover, Doppler auscultation was superior in the detection of impaired ventricular relaxation. Since the physics of Doppler auscultation and classic auscultation are different, it has been suggested that both methods could complement each other. A military noise-immune Doppler based stethoscope has recently been developed for auscultation of patients in loud sound environments (up to 110 dB).


3D-printed

A 3D-printed stethoscope is an open-source medical device meant for
auscultation :''For the ancient monasterial worker, see Auscultare'' Auscultation (based on the Latin verb ''auscultare'' "to listen") is listening to the internal sounds of the body, usually using a stethoscope The stethoscope is an acoustic medical ...

auscultation
and manufactured via means of 3D printing.Official project site
at GitHub
The 3D stethoscope was developed by Dr. Tarek Loubani and a team of medical and technology specialists. The 3D-stethoscope was developed as part of the Glia project, and its design is open source from the outset. The stethoscope gained widespread media coverage in Summer 2015. The need for a 3D-stethoscope was borne out of a lack of stethoscopes and other vital medical equipment because of the blockade of the Gaza Strip, where Loubani, a Palestinian-Canadian, worked as an emergency physician during Operation Pillar of Defense, the 2012 conflict in Gaza. The 1960s-era ''David Littmann, Littmann Cardiology 3'' stethoscope became the basis for the 3D-printed stethoscope developed by Loubani.


Esophageal

Prior to the 1960s, the esophageal stethoscope was a part of the routine intraoperative monitoring.


Earpieces

Stethoscopes usually have rubber earpieces, which aid comfort and create a seal with the ear, improving the acoustic function of the device. Stethoscopes can be modified by replacing the standard earpieces with moulded versions, which improve comfort and transmission of sound. Moulded earpieces can be cast by an audiologist or made by the stethoscope user from a kit.


See also

* Doppler fetal monitor * Speaking tube


References


External links


The Auscultation Assistant
provides heart sounds, heart murmurs, and breath sounds in order to help medical students and others improve their physical diagnosis skills

University of Washington School of Medicine
VCU Libraries Medical Artifacts Collection: Stethoscopes
* "The invention of the stethoscope: A milestone in cardiology", analysis of Laennec's text (1819) on
BibNum
' [click 'à télécharger' for English version]. {{Authority control French inventions Medical equipment Medical testing equipment Medical tests Sound technology 1816 introductions