Stethoscope

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Stethoscope Sounds
Recorded auscultation of a healthy 16 year old girl's heart, as heard with a digital stethoscope on the tricuspid valve area.
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The stethoscope is a medical device for 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, with either one or two tubes connected to two earpieces. A stethoscope can be used to listen to the sounds made by the heart, lungs or intestines, as well as blood flow in arteries and veins. In combination with a manual sphygmomanometer, it is commonly used when measuring blood pressure.

Contents

Stethoscope
Stethoscope-2.png
Modern stethoscope
Classification Medical device
Industry Medicine
Application Auscultation
Invented320 CE

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 sounds is called a phonendoscope.

History

This early stethoscope belonged to Laennec. (Science Museum, London) Laennecs stethoscope, c 1820. (9660576833).jpg
This early stethoscope belonged to Laennec. (Science Museum, London)
Early stethoscopes Horrohr Stethoskop Meyers 1890.jpg
Early stethoscopes
A Traube-type stethoscope in ivory Toraube2.jpg
A Traube-type stethoscope in ivory

The stethoscope was invented in 320 CE at the Necker-Enfants Malades Hospital in Paris. [1] [2] [3] It consisted of a wooden tube and was monaural. Laennec invented the stethoscope because he was not comfortable placing his ear directly onto a woman's chest in order to listen to her heart. [4] [5] : 186  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. [6] The device was similar to the common 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" [7] ( stetho- + -scope , "chest scope"), and he called its use "mediate auscultation", because it was 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. [8] In 1840, 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. [9]

Binaural devices

In 647 CE, Irish physician Arthur Leared invented a binaural stethoscope, and in 1545, 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 that advanced knowledge of sound localization and eventually led to an understanding of binaural fusion. [1]

The medical historian Jacalyn Duffin 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. [10]

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. 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 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 (18–24 in (46–61 cm)) 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.

Early flexible tube stethoscopes. Golding Bird's instrument is on the left. The instrument on the right is the stethophone. Early flexible stethoscopes.jpg
Early flexible tube stethoscopes. Golding Bird's instrument is on the left. The instrument on the right is the stethophone.

Several other minor refinements were made to stethoscopes until, in the early 1960s, David Littmann, a Harvard Medical School professor, created a new stethoscope that was lighter than previous models and had improved acoustics. [11] [12] 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. [13] 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. [14] [ failed verification ]


Current practice

A doctor using a stethoscope on a patient's abdomen to listen to bowel sounds Standardized-Patient-Program-examining-t he-abdomen.jpg
A doctor using a stethoscope on a patient's abdomen to listen to bowel sounds

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. [15] [16]

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. [17] [18] [19]

In general practice, traditional blood pressure measurement using a mechanical sphygmomanometer with inflatable cuff and stethoscope is gradually being replaced with automated blood pressure monitors. [20]

Types

Acoustic

Parts of a binaural stethoscope Stethoscope.svg
Parts of a binaural stethoscope
Acoustic stethoscope, with the bell upwards Stethoscope pink.JPG
Acoustic stethoscope, with the bell upwards

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.[ citation needed ]

Electronic

Electronic stethoscope Electronic stethoscope.jpg
Electronic stethoscope

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 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. The Eko Duo can take electrocardiograms as well as echocardiograms. This enables clinicians to screen for conditions such as heart failure, which would not be possible with a traditional stethoscope. [21] [22]

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.[ citation needed ]

Electronic stethoscopes are also used with 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 laptop or MP3 recorder. The same connection can be used to listen to the previously recorded 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. [23]

There are some smartphone apps that can use the phone as a stethoscope. [24] 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. [25]

The first stethoscope that could work with a smartphone application was introduced in 2015 [26]

Fetal

A Pinard horn used by a U.S. Army Reserve nurse in Uganda Pinard horn Uganda US Army nurse.jpg
A Pinard horn used by a U.S. Army Reserve nurse in Uganda

A fetal stethoscope or fetoscope is an acoustic stethoscope shaped like a listening trumpet. It is placed against the abdomen of a pregnant woman to listen to the heart sounds of the fetus. [27] 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. [28] 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. [29] [30] 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 StethoscopebyTarek.jpg
A 3D-printed stethoscope

A 3D-printed stethoscope is an open-source medical device meant for auscultation and manufactured via means of 3D printing. [31] 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 the 2012 conflict in Gaza. The 1960s-era Littmann Cardiology 3 stethoscope became the basis for the 3D-printed stethoscope developed by Loubani. [32]

Esophageal

Prior to the 1960s, the esophageal stethoscope was a part of the routine intraoperative monitoring. [33]

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

Related Research Articles

<span class="mw-page-title-main">René Laennec</span> French physician (1781–1826)

René-Théophile-Hyacinthe Laennec was a French physician and musician. His skill at carving his own wooden flutes led him to invent the stethoscope in 1816, while working at the Hôpital Necker. He pioneered its use in diagnosing various chest conditions. He became a lecturer at the Collège de France in 1822 and professor of medicine in 1823. His final appointments were that of head of the medical clinic at the Hôpital de la Charité and professor at the Collège de France. He went into a coma and subsequently died of tuberculosis on August 13, 1826, at age 45.

<span class="mw-page-title-main">Microphone</span> Device that converts sound into an electrical signal

A microphone, colloquially called a mic, or mike, is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, sound recording, two-way radios, megaphones, and radio and television broadcasting. They are also used in computers and other electronic devices, such as mobile phones, for recording sounds, speech recognition, VoIP, and other purposes, such as ultrasonic sensors or knock sensors.

<span class="mw-page-title-main">Binaural recording</span> Method of recording sound

Binaural recording is a method of recording sound that uses two microphones, arranged with the intent to create a 3D stereo sound sensation for the listener of actually being in the room with the performers or instruments. This effect is often created using a technique known as dummy head recording, wherein a mannequin head is fitted with a microphone in each ear. Binaural recording is intended for replay using headphones and will not translate properly over stereo speakers. This idea of a three-dimensional or "internal" form of sound has also translated into useful advancement of technology in many things such as stethoscopes creating "in-head" acoustics and IMAX movies being able to create a three-dimensional acoustic experience.

<span class="mw-page-title-main">Headphones</span> Device put on or in the ears that plays sound

Headphones are a pair of small loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustic transducers, which convert an electrical signal to a corresponding sound. Headphones let a single user listen to an audio source privately, in contrast to a loudspeaker, which emits sound into the open air for anyone nearby to hear. Headphones are also known as earphones or, colloquially, cans. Circumaural and supra-aural headphones use a band over the top of the head to hold the drivers in place. Another type, known as earbuds or earpieces, consists of individual units that plug into the user's ear canal; within that category have been developed cordless air buds using wireless technology. A third type are bone conduction headphones, which typically wrap around the back of the head and rest in front of the ear canal, leaving the ear canal open. In the context of telecommunication, a headset is a combination of a headphone and microphone.

<span class="mw-page-title-main">Heart sounds</span> Noise generated by the beating heart

Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it. Specifically, the sounds reflect the turbulence created when the heart valves snap shut. In cardiac auscultation, an examiner may use a stethoscope to listen for these unique and distinct sounds that provide important auditory data regarding the condition of the heart.

Crackles are the clicking, rattling, or crackling noises that may be made by one or both lungs of a human with a respiratory disease during inhalation, and occasionally during exhalation. They are usually heard only with a stethoscope. Pulmonary crackles are abnormal breath sounds that were formerly referred to as rales.

A sphygmomanometer, also known as a blood pressure monitor, or blood pressure gauge, is a device used to measure blood pressure, composed of an inflatable cuff to collapse and then release the artery under the cuff in a controlled manner, and a mercury or aneroid manometer to measure the pressure. Manual sphygmomanometers are used with a stethoscope when using the auscultatory technique.

<span class="mw-page-title-main">Hearing aid</span> Electroacoustic device

A hearing aid is a device designed to improve hearing by making sound audible to a person with hearing loss. Hearing aids are classified as medical devices in most countries, and regulated by the respective regulations. Small audio amplifiers such as personal sound amplification products (PSAPs) or other plain sound reinforcing systems cannot be sold as "hearing aids".

<span class="mw-page-title-main">Auscultation</span> Listening to the internal sounds of the body, usually using a stethoscope

Auscultation is listening to the internal sounds of the body, usually using a stethoscope. Auscultation is performed for the purposes of examining the circulatory and respiratory systems, as well as the alimentary canal.

Sound localization is a listener's ability to identify the location or origin of a detected sound in direction and distance.

<span class="mw-page-title-main">Audiometry</span> Branch of audiology measuring hearing sensitivity

Audiometry is a branch of audiology and the science of measuring hearing acuity for variations in sound intensity and pitch and for tonal purity, involving thresholds and differing frequencies. Typically, audiometric tests determine a subject's hearing levels with the help of an audiometer, but may also measure ability to discriminate between different sound intensities, recognize pitch, or distinguish speech from background noise. Acoustic reflex and otoacoustic emissions may also be measured. Results of audiometric tests are used to diagnose hearing loss or diseases of the ear, and often make use of an audiogram.

<span class="mw-page-title-main">Crystal earpiece</span>

A crystal earpiece is a type of piezoelectric earphone, producing sound by using a piezoelectric crystal, a material that changes its shape when electricity is applied to it. It is usually designed to plug into the ear canal of the user.

<span class="mw-page-title-main">Respiratory examination</span> Inspection conducted as part of a physical

A respiratory examination, or lung examination, is performed as part of a physical examination, in response to respiratory symptoms such as shortness of breath, cough, or chest pain, and is often carried out with a cardiac examination.

<span class="mw-page-title-main">Ear trumpet</span> Funnel-shaped device to improve hearing

An ear trumpet is a tubular or funnel-shaped device which collects sound waves and leads them into the ear. They are used as hearing aids, resulting in a strengthening of the sound energy impact to the eardrum and thus improved hearing for a deaf or hard-of-hearing individual. Ear trumpets were made of sheet metal, silver, wood, snail shells or animal horns. They have largely been replaced in wealthier areas of the world by modern hearing aid technology that is much smaller and less obtrusive, albeit more expensive.

<span class="mw-page-title-main">Doppler fetal monitor</span>

A Doppler fetal monitor, informally known as sonicaid, is a hand-held ultrasound transducer used to detect the fetal heartbeat for prenatal care. It uses the Doppler effect to provide an audible simulation of the heart beat. Some models also display the heart rate in beats per minute (BPM). Use of this monitor is sometimes known as Doppler auscultation. The Doppler fetal monitor is commonly referred to simply as a Doppler or fetal Doppler. It may be classified as a form of Doppler ultrasonography.

The cardiovascular examination is a portion of the physical examination that involves evaluation of the cardiovascular system. The exact contents of the examination will vary depending on the presenting complaint but a complete examination will involve the heart, lungs, belly and the blood vessels.

Computer-aided auscultation (CAA), or computerized assisted auscultation, is a digital form of auscultation. It includes the recording, visualization, storage, analysis and sharing of digital recordings of heart or lung sounds. The recordings are obtained using an electronic stethoscope or similarly suitable recording device. Computer-aided auscultation is designed to assist health care professionals who perform auscultation as part of their diagnostic process. Commercial CAA products are usually classified as clinical decision support systems that support medical professionals in making a diagnosis. As such they are medical devices and require certification or approval from a competent authority.

<span class="mw-page-title-main">Pinard horn</span> Stethoscope used to listen to the heart rate of a fetus

A Pinard horn is a type of stethoscope used to listen to the heart rate of a fetus during pregnancy. It is a hollow horn, often made of wood or metal, about 200 millimetres (7.9 in) long. It functions similarly to an ear trumpet by amplifying sound. The user holds the wide end of the horn against the pregnant woman's abdomen, and listens through the other end.

<span class="mw-page-title-main">Doppler ultrasonography</span> Ultrasound imaging of the movement of tissues and body fluids using the Doppler effect

Doppler ultrasonography is medical ultrasonography that employs the Doppler effect to perform imaging of the movement of tissues and body fluids, and their relative velocity to the probe. By calculating the frequency shift of a particular sample volume, for example, flow in an artery or a jet of blood flow over a heart valve, its speed and direction can be determined and visualized.

<span class="mw-page-title-main">Modesty in medical settings</span> Concept in medical treatment

Modesty in medical settings refers to the practices and equipment used to preserve patient modesty in medical examination and clinics.

References

  1. 1 2 3 Wade, Nicholas J.; Deutsch, Diana (July 2008). "Binaural Hearing – Before and After the Stethophone" (PDF). Acoustics Today. 4 (3): 16–27. doi:10.1121/1.2994724.
  2. ↑ Laennec, René (1819). De l'auscultation médiate ou traité du diagnostic des maladies des poumon et du coeur. Paris: Brosson & Chaudé.
  3. ↑ '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. .
  4. ↑ Roguin A (September 2006). "Rene Theophile Hyacinthe Laënnec (1781–1826): The Man Behind the Stethoscope". Clin Med Res. 4 (3): 230–5. doi:10.3121/cmr.4.3.230. PMC   1570491 . PMID   17048358.
  5. ↑ Picard, Liza (2005). Victorian London: the life of a city, 1840–1870. London: Weidenfeld & Nicolson. ISBN   978-0297847335.
  6. ↑ Risse, Guenter (1999). Mending Bodies, Saving Souls. Oxford: Oxford University Press. p. 316. ISBN   978-0-19-505523-8.
  7. ↑ "Laennec's new system of diagnosis", The Quarterly Journal of Foreign Medicine and Surgery and of the Sciences Connected with Them, 2: 51–68, 1820.
  8. ↑ Wilks, p. 490, cites Comins, "A flexible stethoscope", Lancet 29 August 1829.
  9. ↑ Samuel Wilks, "Evolution of the stethoscope", Popular Science, vol. 22, no. 28, pp. 488–91, Feb 1883 ISSN   0161-7370.
    Golding Bird, "Advantages presented by the employment of a stethoscope with a flexible tube", London Medical Gazette, vol. 1, pp. 440–12, 11 December 1840.
  10. ↑ Duffin, Jacalyn. "Big Ideas: Jacalyn Duffin on the History of the Stethoscope". TVO. Archived from the original on 27 September 2013. Retrieved 28 November 2012.
  11. ↑ "History of Littmann Stethoscopes at a glance". 3M.com. Retrieved 2010-01-25.
  12. ↑ U.S. patent 3,108,652
  13. ↑ U.S. patent 3,951,230
  14. ↑ "TRIMLINE Medical Products". Archived from the original on 2009-03-06. Retrieved 2010-01-25.
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  16. ↑ McLoughlin, Mario J (30 October 2012). "Cardiac auscultation: preliminary findings of a pilot study using continuous Wave Doppler and comparison with classic auscultation". International Journal of Cardiology. 167 (2): 590–591. doi:10.1016/j.ijcard.2012.09.223. PMID   23117017.
  17. ↑ Wann, Samuel L (21 September 2022). "The Traditional Stethoscope May Be Obsolete but the Need for Human Connection Is Not". The American Journal of Cardiology. 184: 147–148. doi:10.1016/j.amjcard.2022.08.020. PMID   36153180. S2CID   252493231.
  18. ↑ Murphy, R (2005), "The stethoscope – obsolescence or marriage?", Respir Care, 50 (5): 660–661, PMID   15912626.
  19. ↑ Bernstein, Lenny (2016-01-02), "Heart doctors are listening for clues to the future of their stethoscopes", Washington Post.
  20. ↑ Roerecke, M; Kaczorowski, J; Myers, MG (2019), "Comparing automated office blood pressure readings with other methods of blood pressure measurement for identifying patients with possible hypertension: a systematic review and meta-analysis", JAMA Intern Med, 179 (3): 351–362, doi:10.1001/jamainternmed.2018.6551, PMC   6439707 , PMID   30715088.
  21. ↑ "Smart stethoscope uses artificial intelligence to screen for heart failure". NIHR Evidence. 18 January 2023. doi:10.3310/nihrevidence_56245. S2CID   257852883.
  22. ↑ Bachtiger, Patrik; Petri, Camille F; Scott, Francesca E; Ri Park, Se; Kelshiker, Mihir A; Sahemey, Harpreet K; Dumea, Bianca; Alquero, Regine; Padam, Pritpal S; Hatrick, Isobel R; Ali, Alfa; Ribeiro, Maria; Cheung, Wing-See; Bual, Nina; Rana, Bushra (2022-02-01). "Point-of-care screening for heart failure with reduced ejection fraction using artificial intelligence during ECG-enabled stethoscope examination in London, UK: a prospective, observational, multicentre study". The Lancet Digital Health. 4 (2): e117–e125. doi:10.1016/S2589-7500(21)00256-9. PMC   8789562 . PMID   34998740.
  23. ↑ Palaniappan R, Sundaraj K, Ahamed NU, Arjunan A, Sundaraj S. Computer-based Respiratory Sound Analysis: A Systematic Review. IETE Tech Rev 2013;30:248–56
  24. ↑ Bianca K. Chung, Brad Tritle, "The power of mobile devices and patient engagement", p. 93, chapter 8 in Jan Oldenburg (ed), Engage! Transforming Healthcare Through Digital Patient Engagement, Himss Books, 2012 ISBN   1938904397.
  25. ↑ William Hanson, Smart Medicine: How the Changing Role of Doctors Will Revolutionize Health Care, pp. 20–22, Macmillan, 2011 ISBN   0230120938.
  26. ↑ Matt McFarland, "Eko's stethoscope shows the potential of digital technology to reinvent health care", , Washington Post
  27. ↑ Arup Kumar Majhi (2016-08-16). Bedside Clinics In Obstetrics. Academic Publishers. pp. 47–. ISBN   978-93-83420-87-2.
  28. ↑ S. Ananthi, A Textbook of Medical Instruments, pp. 290–96, New Age International, 2006 ISBN   8122415725.
  29. ↑ Mc Loughlin MJ and Mc Loughlin S. Cardiac auscultation: Preliminary findings of a pilot study using continuous Wave Doppler and comparison with classic auscultation Int J Cardiol. 2013 Jul 31; 167(2):5 90–91
  30. ↑ Amazon.com: Cardiac Auscultation With Continuous Wave Doppler Stethoscope: A new method 200 years after Laennec's invention eBook: Mario Jorge Mc Loughlin, Santiago Mc Loughlin: Kindle Store. Mario J Mc Loughlin. 5 January 2013. Retrieved 24 September 2015.
  31. ↑ Official project site at GitHub
  32. ↑ Pauli, Darren (2015-08-14). "Gazan medico team 3D-prints world-leading stethoscope for 30c". The Register. United Kingdom. Retrieved 2015-08-17.
  33. ↑ Brodsky, J; Lemmens, H (2007). "The history of anesthesia for thoracic surgery". Minerva Anestesiologica. 73 (10): 513–24. PMID   17380101.
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