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Tuesday, October 20, 2020

Stethoscope: Types, Uses and Function

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The stethoscope is a medical device for auscultation, which means listening to the sounds made internally in an animal or human body. It commonly possesses a tiny disc-shaped resonator that is positioned against the skin and one or two tubes attached to two earpieces.

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A stethoscope can be employed to listen to the sounds made by the lung, intestines, or as blood flow in veins and arteries, and as well as the heart. In can also be used alongside a sphygmomanometer, in measuring the blood pressure.

The stethoscope was first invented in Necker-Enfants Malades Hospital by René Laennec in France in 1816. It comprised of a wooden tube and was monophonic.

Laennec discovered the stethoscope because he was uncomfortable positioning his ear directly into a woman’s chest to listen to her heart. He discerned that a rolled piece of paper, placed between the doctor’s eye and the patient’s chest, could amplify heart sounds without requiring direct contact.

Laennec’s invention was identical to the standard ear trumpet, a traditional form of hearing aid; indeed, his invention was nearly indiscernible in structure and function from the trumpet, which was normally called a “microphone.”

Laennec called his invention the “stethoscope” (stetho- + -scope, “chest scope”), and he called its use “mediate auscultation” because it was auscultation with a device intermediary between the physician’s ear and patient’s body (Presently auscultation indicates all such listening or mediation.)

In 1851, Irish physician Arthur Leared developed a binaural stethoscope, and in 1852, George Philip Cammann improved the layout of the stethoscope instrument (so it could be used for both ear) for commercial production, which has become the standard ever since.

Twenty-five years after Laennec designed the first stethoscope, George P. Camman from New York formulated a new design that featured an earpiece for both ears, further improving on the work already done by Arthur Leared.

Medical personnel continued using this design with few changes for almost a century. It wasn’t until the early 1960s that Dr. David Littmann patented a new design that significantly improved the acoustical performance of the stethoscope.

3M acquired Dr. Littmann’s stethoscope business a few years later, and the doctor continued to work on his designs. Dr. Littmann’s designs ultimately became the new standard for stethoscopes, and now Littmann is the most trusted brand name in the business.

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By 1873, there were illustrations of a different kind of stethoscope that could connect to slightly different areas to create a minor stereo effect, although this did not evolve to become a standard tool in clinical practice.

A medical historian Jacalyn Duffin has asserted that the invention of the stethoscope commemorated a major step in the reexamination of disease from being a bunch of symptoms to the modern sense of a disease as a complication with an anatomical system even if there are no evident symptoms.

This re-definition happened in parts.

Parts of a Stethoscope

No matter the type of stethoscope, specialty, or not, all stethoscopes have the same fundamental designs and parts. Listed below are the main components of a stethoscope.

Ear tips

These tips sit at the ends of a curved metal tube that attaches to the rubber ducts. The tips can fit comfortably in the ears, so one can clearly hear the sounds of the body as one auscultates.

Some stethoscope models offer varied sizes of ear tips so one can find the right size and fit.

Tube

The tube has two significant jobs which are transmitting sounds from the body while simultaneously eliminating background noise that might interfere with the doctor’s diagnosis.

A good tube must be made from thick, flexible, crack-resistant, and durable material that will withstand a lot of bending.

Chest piece

The chest piece (or head) of most stethoscopes is crafted from stainless steel, which is very durable, and postures sound well. Some chest pieces can also be made from a combination of stainless steel and an aluminum alloy or zinc.

The common double head stethoscope chest piece is characterized by a diaphragm on one side and a bell on the other.

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Diaphragm

The diaphragm is a thin, round piece of pliable material like resin that fits one side of the metal stethoscope head. The diaphragm amplifies sound, and it should be well-sealed, considerably with a non-chill rim, for optimal diagnosis as the doctor monitors patient using a stethoscope

Head Types

An even standard acoustic stethoscope has numerous options for the head design. The three main models are;

Single Head

Single head stethoscopes offer only one flat, disc-shaped surface for listening to internal organs of the body like the lungs and the heart. Single head stethoscopes usually cover a wide frequency of sounds and allow the user to focus on either the higher or lower end of the spectrum.

Dual Head

Dual head stethoscopes have doubles heads, one on each side of the chest piece. The larger one is called the diaphragm–are flatter and functions better for high-frequency sounds. The smaller one, which is the bell, resembles an elongated cup and functions best on low-frequency sounds.

Some Doctors who attend to patients of all ages like a dual head stethoscope because the diaphragm side works better for adult patients, while the bell side is more suitable for pediatric patients.

Triple Head

The most unusual three stethoscope head options feature three heads attached to a single chest piece. This design is heavy and uncomfortable to use, which is why it’s only used for critical cardiac examination.

Most physicians, nurses, and other medical personnel use a standard single or double head model. Other parts of a stethoscope include tubing, stem, ear tube and headset.

Specific Stethoscope Uses

Some stethoscopes are designed to specific types of patients or have designs that are intended to aid certain functionalities. The options are:

Cardiology

As the name implies, cardiology stethoscopes are used in cardiac examination to discern between the different sounds of the heart to arrive at the precise diagnosis. Both single head and double head chest pieces are available.

Pediatric

A pediatric stethoscope resembles a regular stethoscope, with a slight alteration; the head is smaller; it’s about an inch in diameter, so it will be more proportional to pediatric patients who need small medical instruments.

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Infant stethoscopes, which feature even smaller chest pieces, are available.

Veterinary

There is a veterinary stethoscope specially designed to be used on animals such as dogs and cats. Some veterinarians also use pediatric or infant stethoscopes to treat smaller animals, such as lizards and birds.

Sprague Rappaport

This design of a stethoscope is characterized by two tubes that reach directly from the stethoscope chest piece to the curved metal earpiece. The tubes are connected together with metal clips so they cannot separate.

The double-barreled design helps to enhance sound quality.

Types of Stethoscopes

Neonatal

A neonatal stethoscope is the smallest and for newborn patients. The smallest diameter of the chest piece can be as small as 2cm, and it allows for accurate auscultation without excess background noise.

Most types of neonatal stethoscope feature a non-chill rim and non-latex parts. Though a regular size chest piece can be used for small patients, it’s not easy to place the chest piece to listen to certain sounds that aren’t in the middle of the chest.

The smaller size helps more accurate diagnosis in a shorter period of time since the user doesn’t have to continually adjust.

Infant

The infant stethoscope resembles the pediatric stethoscopes, but the size is in between the two. The chest piece is about 2.7cm, and it gives accurate auscultation for smaller patients.
This stethoscope also features a non-chill rim, and non-latex formulation to deter any allergic reactions.

Pediatric

A pediatric stethoscope resembles regular adult stethoscopes, but the differences are in the size of chest piece and color. For a pediatric patient, it might not be easy to place the chest piece since, generally, children have a smaller chest size much smaller than an adult.

Like neonates and infants, using an adult stethoscope on a pediatric patient puts the user at risk of background sound interference. The pediatric stethoscope decreases the size of the chest piece, which helps for more precise placement.

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They can also be made of materials that are likely to be warmer so that the doctor has more chance of keeping the patient still for diagnosis. The other benefit of choosing this type of stethoscope is the color.

Although color might not seem advantageous, when diagnosing a pediatric patient who might be frightened or uncomfortable, a toy like a stethoscope can be engaging to the patient.

Fetal

The original fetal stethoscope, also called a fetoscope, was invented in the 19th century and was then an ear horn and called the Pinard Horn, it amplified the fetal heartbeat into the ear.

Conventionally, the binaural fetoscope, a modern combination of the stethoscope and the pinned horn, is available. The difference between a fetal stethoscope and other kinds of the stethoscope is the construction.

With the fetal stethoscope, a distinct bell is placed against the mother’s stomach to transmit sound to the earpieces. Another feature is the forehead piece that helps the physician to both place the bell and transmits sound.

The sound of the heartbeat from a fetoscope is faint, and very different than that of the fetal doppler, amplifies. Some fetoscopes, especially the Leff fetoscope, even separate the heart tones from placental pulses.

The bell is larger and provides sound quality that rivals the doppler.

Cardiology

A cardiology stethoscope is another that looks like a regular stethoscope, but the distinction is that the cardiology variation gives the user a better acoustic quality, and the ability to hear high and low frequency sounds better.

With these, the user can hear even faint sounds like clicks and rubs, making sure the doctor doesn’t miss even subtle sounds.

Not only the sound quality, but the earpieces are thicker and more comfortable, blocking out background noise so that they don’t interfere with listening. The tubes are thicker and tend to be shorter between the earpieces and the diaphragm to retain sound quality.

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Veterinary

Veterinary personnel uses exactly the same stethoscope as doctors with human patients, but this doesn’t have to be the case. Animals have different needs and peculiarities that aren’t pertinent to humans.

For instance, an animal’s fur can make a lot of ambient noise that can interfere with auscultation. The first design benefit is that most veterinary brands have long tubing; some can be about 32 inches.

This allows the Vet, some distance from nervous or feral animals, or simply more comfort working with larger animals. And another feature is a tunable diaphragm.

This allows for adjustments with the brush of a switch making it easier to transit between high and low sounds frequency. When working with animals, fast and easy transitions can be the difference between a successful and unsuccessful diagnosis.

Tunable diaphragms also help with amplification for low sounds that can be masked by fur.

Teaching stethoscope

This type of stethoscope has single-lumen tubing that is very durable. It also comes with a defined stainless chest piece and has a dual headset. This feature helps the teacher and the student to use the stethoscope at together.

They are mostly used for teaching purposes.

Conclusively, although many stethoscopes are analog, using designs that amplify sounds naturally, there is another type of stethoscopes that makes use of modern technology to aid in auscultation.

Electronic

Acoustic stethoscopes have a sound problem, precisely volume. An electronic stethoscope resolves this problem by electronically amplifying the sound obtained from the chest piece and transforming it to electronic waves transmitted through a particularly designed electrical system.

The sounds are then processed for better auscultation. Acoustic stethoscopes use the same physics, so the sound is the same across the circuitry.

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With electronics, there are different ways of converting the sound. The most fundamental is the use of a microphone placed in the chest piece, but this gives off background noise interference.

Some employ the use of a piezoelectric crystal at the head of a metal shaft, or in the foam piece beneath the diaphragm. Some use an electromagnetic diaphragm.
Electronic Stethoscopes come in two types: Digitizing and Amplifying.

Amplifying

If a user has any type of hearing loss, using any other type of stethoscope will be difficult for diagnosis.

Amplified stethoscopes aid the conversion of the acoustic sound of auscultation into electronic sound waves, which are then amplified and transmitted to the earpiece.

Because the sound is electronic, users can do all types of beneficial things to it, such as reduction of ambient noise interference. It also allows the user to wear headphones so the earpieces don’t interfere with any hearing aids one might be wearing.

Other features include an electronic display for readings and the ability to switch between the bell and diaphragm for low sounds and for high sounds consecutively.

Digitizing

Digital stethoscopes offer the chance to make the adjustment between analog and digital amplification.

This adjustment mode allows the user to pick the ideal setting for different types of diagnostic sounds. Many let you evaluate visually with a record feature, and some can connect those recordings wirelessly to a smart device or computer.

Most offer rechargeable batteries for easy use and plenty of amplification levels to make the diagnosis process easier and efficient.

Stethoscope
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Disclaimer: This article is purely informative & educational in nature and should not be construed as medical advice. Please use the content only in consultation with an appropriate certified medical or healthcare professional.

Jennifer Aigbini
I am a language enthusiast, studying Linguistics at the University of Benin, in Nigeria.
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