Stethoscope.

Introduction:

A Conventional Stethoscope.

A stethoscope is a medical device that is used, generally, by doctors, nurses, and other medical professionals. They use it predominantly to perform checks on the heart and lung functions. These checks are called ‘auscultations’. Usually, heart function and lung function sound routine and clean. So if there are any murmurs that occur during the auscultation, the medical professionals will know something is up and further investigation is needed.

To a lesser degree mechanics also use stethoscopes. During the running of an engine, stethoscopes can be used to determine any faults that might happen in the cylinder of a combustion engine. Unfortunately, you cannot open a cylinder during a running engine to check out faults as this would intervene with the normal functioning of an engine. Therefore a stethoscope allows them to perform diagnostics on the engine. Much like a medical professional with a human body.

History of the Stethoscopes:

It was invented in France by the french scientist Rene Laennec in Paris. This innovation came from necessity. He felt uncomfortable placing his ears on women’s chests in order to listen to heart sounds. As a result, he decided to come up with a device that would add a little bit more distance between him and his patients.

Painting of Laennec using his stethoscope on a child.

The first prototype he came up with looked like an ocular device pirates would use. He would place his ear on one end of this primitive stethoscope and the other end would end up on his patients’ chests. The design for this device has a lot of similarities with an old hearing aid device called an “ear trumpet”. 

An Ear Trumpet; used to amplify sound.

Rene noticed that a rolled-up notebook would amplify the sound of a beating heart without physical contact with the patient. He called his device a stethoscope. The term stethoscope has its origins in Ancient Greek. “Stethos” means chest and “Scope” which can be loosely translated as a listening device.

The earliest forms of stethoscopes that resemble the ones we know today came out in 1855 and were invented by Golding Bird. These were the first ones to feature flexible tubing. This next level of innovation was meant to provide extra comfort to the people performing auscultations.

Golding Bird with His Invention.

Current Practice:

Stethoscopes, as we know them today, are arguably the most recognizable piece of medical equipment out there. They are THE sign of medical professionals. Studies have also shown that images of people in lab coats get a huge bump in confidentiality if they have a stethoscope draped around their neck. Automatically people associate stethoscopes with the trustworthiness of a doctor. Even though mechanics, albeit to a lesser degree, are frequent users of stethoscopes as well.

There are those that say that slowly but surely the stethoscope is becoming obsolete. The rise of portable ultrasound devices is slowly phasing out the stethoscopes in hospitals. At least when it comes to cardiovascular research, in checking lungs and bowels for signs of disease however the stethoscope still has its place. However only time will tell for how long.

 Names of the Stethoscope Parts:

Some Parts of a Conventional Stethoscope.

1. Ear tips
2. Ear tube
3. Tubing
4. Headset
5. Stem
6. Chest-piece
7. Diaphragm
8. Bell

When properly combined together these parts create a functioning stethoscope, which allows medical professionals to listen to a wide range of sounds so that they can quickly determine and treat potential medical issues.

• Ear Tips:

The ear tips of a stethoscope are the part that goes into the user's ear where they receive the sounds that come from the chest piece. The ear tips are generally made out of rubber or silicone material and are designed to create a form-fitting seal inside of the ears so that unwanted sounds stay out.

A good pair of comfortable ear tips are very important for users who spend a lot of time checking their patients’ health with their stethoscopes as it can make all the difference between a comfortable experience and an irritating or painful one.

All ear tips are made with a soft, flexible material that is structured to fit and cradle the inner ears, a clear whole in the center so that the sound can easily transfer through them, and either a rigged or smooth interior on the opposite end of the ear tips where the top end of the tubes of the stethoscope slide in.

Due to their small size and inexpensive price ear tips are one of the easiest items a person can replace on a stethoscope to improve their experience, and it can even add a little increase to the sound quality of the stethoscope.

• Ear Tube:

The ear tubes are the metal/steel parts of the stethoscope that connect to the ear tips and the synthetic or PVC tubing, which connects to the stem of the chest piece. The ear tubes are designed to isolate and transfer sound to the user’s ears with minimum quality loss.

These metal/steel ear tubes help separate sounds into left and right channels in order to provide a better sound experience, which allows the user to more easily diagnose their patients’ medical condition. As mentioned previously the bottom section of the ear tubes connect to the stethoscope's tubing line where it receives the incoming sounds.

• Tubing:

The soft flexible line of the stethoscope is known as its tubing. The purpose of the tubing is to maintain and transfer the frequency/sound level that is captured by the diaphragm or bell and send it to the ear tubes where it can make its way to the user’s ears. Depending on the stethoscopes make and model the tubing may be made with a single tube or dual lumen tube design that connects to the metal/steel tubes.

A good stethoscope will usually come with a dual lumen design and tubing that is sectioned off into left and right hemispheres so that the diaphragm/bell sounds can travel from the head of the device to the user’s ears with the most accuracy and acuity.

• Headset:

The headset is the combined components of the upper half of the stethoscope which include the ear tubes, tension springs, and ear tips. All of the components are designed together to form a comfortable alignment in the users' ears and are angled in a way that provides maximum sound quality throughout the headset.

When viewed from the side the ear tips of the headset can be seen pointed toward the user’s nose while the ear tubes hang back slightly. This allows sound to flow efficiently into the ear canal so that there is minimal disturbance from the stethoscope.

• Stem:

The stem is basically the metal/steel part of the stethoscope that connects the tubing of the stethoscope to the chest piece. Aside from connecting the two components of the stethoscope it also allows the user to switch/click between the chest-pieces diaphragm and bell by turning the chest-piece and clicking it into place via the ball bearing.

• Chest-Piece:

The chest piece or head of the stethoscope is composed of the connected stem, diaphragm, and/or bell. Depending on the stethoscope it may feature either a single-head or dual-head design that may or may not contain a lower-frequency bell. As far as function goes the chest-piece part of the stethoscope is used to listen to patient sounds by placing the diaphragm or bell end of the chest piece on the patient’s chest, back, or stomach. Most chest pieces work best when applied against the patient's skin, however, some stronger, high-quality stethoscopes may be able to pick up sounds through thin layers of clothing.

• Diaphragm:

The diaphragm is the large circular end of the chest piece. This side of the device allows medical professionals to listen to a wider area of the patient’s body and picks up higher frequency sounds than the bell half of the chest piece. Some diaphragms feature a non-chill, hypoallergenic diaphragm in order to ensure maximum comfort for the patient being observed.

• Bell:

The bell is the smaller circular end of the chest piece. This side of the device focuses on a narrower range of listens for lower-frequency sounds that may not easily be detected by the diaphragm. As with the diaphragm, the bell may also feature a non-chill, hypoallergenic design to provide patients with additional comfort while they are being listened to.

Working Principle of the Stethoscope:

A stethoscope is a medical device designed to pick up body sounds through vibrations and transmit them to our ears. They are usually composed of a flat or curved chest piece covered highly by a film, like a drum, called the diaphragm. As sound vibrations reach the diaphragm, this vibrates and amplifies these sounds, transmitting them through the sealed hollow tubing into the earpieces and into the user’s ears.

Types of Stethoscopes:

     1. Acoustic:

An Acoustic Stethoscope.

Probably the best-known stethoscope-type. They operate on the transmission of sound from the chest piece to the listeners’ ears, via air-filled hollow tubes. The chest piece usually consists of 2 sides that can be placed on the patients’ chest. A bell and a diaphragm.

If the diaphragm is placed on the patients’ chest, acoustic airwaves are produced by the vibration of the plastic diaphragm which travels through the tubing to the listeners’ ears. If the bell is used then the vibrations are directly transmitted to the listeners’ ears. The diaphragm is used to hear high-frequency sounds while the bell best delivers low-frequency sounds. Both are necessary to conduct a full scale auscultation. This two-sided stethoscope was invented by Rappaport and Sprague in the early part of the 20th century. Both also have stethoscope types named after them.

One major issue with acoustic stethoscopes has always been that the sound level is really low. This problem was overcome however in 1999 with the invention of the stratified continuous lumen, and the kinetic acoustic mechanism in 2002.

 

    2. Electronic:

The main function of these types of stethoscopes is that they convert analog sound signals into digital ones. This can be achieved in one of two ways:

Electronic Stethoscope.

1. The first way in which this is done is by placing a microphone in the chest piece. However this method has a lot of drawbacks. By amplifying the sound directly it has to deal with a lot of background noise that will be inadvertently amplified as well. This can seriously hinder an auscultation.
2. Another way to do this, using a piezo-electric crystal. Piezoelectric crystals work in such a way that when pressure is applied to them (think a heartbeat), a small electric charge is released. As a result, ambient noise is filtered out and you only hear the actual heartbeat in digital form.

The big benefit of electronic stethoscopes is that it can store a patient’s auscultation to form a base-file of that patient. It will always have a future reference to go to if need to hear or find something out of place. Secondly as the sounds they produce are digital, we can add a splitter device to the acoustic-outlet. This enables us to add a second pair of headphones. As a result, in the teaching process, the professor and all students can listen in on the same auscultation and the professor can show the students what to look out for.

     3. Fetal:

A Fetal Stethoscope.

A fetal stethoscope or a fetoscope looks a lot like the old listening trumpet. The device works by placing one end of the stethoscope on the pregnant woman’s abdomen. This allows the listener to listen to the heartbeat of the fetus. A fetoscope is also called a Pinard horn after the French obstetrician Adolphe Pinard.

     4. Doppler:

A Doppler Stethoscope.

A Doppler stethoscope works using the famed ‘Doppler-Effect’. Motion is detected by the change in frequency of the soundwaves. As a result, stethoscopes that use the doppler effect as the main detection principle have been shown to be more sensitive in the detection of aortic regurgitations and the detection of impaired ventricular relaxation.

Methods of Using a Stethoscope:

General:

• Wherever possible it is recommended to do an auscultation in a quiet space. For EMT’s (Emergency Medical Technicians) however, this is not always possible and for them, different stethoscopes have been developed. Mostly the stethoscopes they use have special noise-dampening technology to muffle out the background noise.
• The reason why you need to do an auscultation in a quiet space seems self-evident. It is important you focus fully on the sounds you want and need to hear. A noisy environment will only distract you too much from the job at hand.
• Next, it is important to keep in mind that the positioning of the patient plays an important role during the auscultation. A patient’s lungs can sound different whether he or she is laying on his/her side or sitting up etc. To listen to the heart and abdomen it’s recommended for your patient to lay down. However for the lungs you’ll find it easier if the patient is sitting up.

Using the Chest Piece Properly:

Thirdly you need to decide if you want to go for the high-pitched or low-frequency sounds. The chest piece on your stethoscope most likely will have 2 sides. One’s a bell and the other one is a diaphragm as described in the sections above.

Labeled image of a Stethoscope.

The diaphragm basically is a plastic sheet that transmits vibrations from your skin and delivers them via the tubing to the listener’s ears. It is this side you have to use to hear medium to high-pitched sounds.

On the other hand, the bell-side is just a chamber that forms between the chest piece and your patient’s chest. The change in volume of this chamber as a result of for example heart beats causes sound waves to travel via the tubing to the listener’s ear. Use this site for the low-pitched sounds.

Note: Always use the chest piece on bare skin. If your patient still has clothes on while you use your stethoscope chances are you’ll hear nothing but rustling. The same issue persists if you treat someone who is overly hairy. Unfortunately in that case there is nothing the patient can do about it other than shave everything off. However, if you face a particularly hairy patient, keep the chest piece still to keep the rustling to a minimum.

Cleaning and Maintenance of Stethoscopes:

A stethoscope is a hardworking tool. It rarely complains, but there are a few things you can do to keep it healthy and happy.

• Inspect the stethoscope occasionally to make sure there is no obvious damage such as punctured tubing or cracked earpieces.
• Wipe the earpieces and chest-piece regularly with 70 percent isopropyl alcohol to clean and disinfect them.
• The tubing may be cleaned with 70 percent isopropyl alcohol or mild soapy water.
• If you wear the stethoscope draped around your neck, always keep it around your collar. The flexible tubing may become stiff if it is continuously exposed to skin.
• The stethoscope should not be exposed to solvents, oils, extreme heat or extreme cold, as these could cause the materials to degrade.
• Keep the manual that came with the stethoscope and follow any care and maintenance tips it suggests.

For Further Reading…......

Inspecting the Heart:

Heart sounds are generally medium to high-pitched. So in order to study the heart, you need to use the diaphragm on your stethoscope. Place the diaphragm on the patient’s chest. Try to place it in such a way that the diaphragm covers the space on the left upper chest, where the 4th and 6th rib meet. This is almost directly under the breast. Then hold the chest piece between your index and middle finger. Gently apply pressure until you do not hear your fingers rubbing together anymore.

Heart Auscultation Position.

Ask the patient to breathe normally. Try to listen to the heart for a full minute. During this time you should hear a sound which is best described as a “lub-dub”-sound. Of course it is hard to convey a sound through written text but, “lub-dub” comes pretty close to what you will hear in real life.

These “lub” and “dub” sound also have their own, more scientific names:-

1. The “lub”- or systolic-sound happens when the mitral and tricuspid valves of the heart close.
2. The “dub”-sound, or diastolic, happens when the aortic and pulmonic valves close.

Count the Number of Heartbeats:

Usually, a normal person’s resting heart rate can be anything between 60 and 100 beats per minute. A well-trained athlete however will have a bigger heart. As a result, the heart will need to pump less per minute to circulate blood around the body.

• A well-trained athlete’s resting heart rate lies between 40-60 beats per minute.
• For infants and kids under 10 years old the normal heart-beat per minute range varies per age. For newborns, it is very fast. Between 70-190 BPM.
• However then as the kid matures, their heart grows and has to beat less to keep the blood flowing. Once a child turns 2 their heartbeats already between 80-130 BPM.
• Children between 7 - 9 have a heartbeat between 70-110 BPM.

What to Listen for When Using a Stethoscope:

First up if the heart-rate is elevated from the normal, that might be a sign of an underlying condition, or it can be that the patient is just nervous to be examined. That is why it is important to get a good understanding of how the patient behaves under normal circumstances.

However even for the untrained ear; here are some pointers to look out for:-

• If you hear a sound that is more like “lub…shhhh…dub”, that might point to a heart murmur. A heart murmur is caused when blood rushes too quickly through the valves.
• If you hear one there is still not an immediate cause for concern as most people do have benign heart murmurs from time to time. However, you should advise the patient to go check it out if you do detect one.
• If you hear another sound, other than the familiar “lub-dub” then the patient might have a ventricular defect. This third heart sound is referred to as S3 or a ventricular gallop. It sounds like a low-frequency vibration. Advise the patient to go see a doctor if you hear this third heart sound.

Listen for Bruits:

The word “bruit” comes from the French word “bruit” and means “noise”. Usually when you detect a heart murmur in the patient you might want to check out if there are any bruit sounds. They sound similar but are checked in completely different places.First, you need to place your stethoscope using the diaphragm side over one of the carotid arteries. The carotid arteries are 2 big arteries that run in the front of your neck, on either side of the Adam’s apple.

Carotid Arteries.

Be careful not to press too hard on the artery as you could cut off blood supply to the brain and cause your patient to faint. Never block off both arteries either as this surely will result in fainting. This is what MMA’s (Mixed Martial Art) famous “choke-hold” is based on.

A bruit makes a whooshing sound that indicates an artery is narrowed. Here’s usually where the confusion happens. A bruit and a heart murmur can sound almost identical. However a bruit will sound much louder when you listen to the carotid arteries rather than the heart. You can also listen for bruits over the abdominal aorta, renal arteries, iliac arteries and femoral arteries.

A constricted artery is a serious medical issue and requires medical attention. Tell the patient to go see a doctor straight away!

Inspecting the Lungs:

Lung Auscultation Positions.

Ask the patient to sit up straight and breathe normally. If you cannot hear any breathing sounds or if the breathing is too shallow to hear any abnormalities then ask your patient to breathe deeper.

Just like when doing a heart auscultation you need to use your diaphragm when checking the patient’s lungs. Listen to the patient’s upper and lower lobes and inspect the front and back.

Normal Breathing Sounds:

Normal breathing sounds are clear and crisp. It sounds like someone would be blowing air into a cup.

Abnormal breath sounds shouldn’t be too hard to pick up with your stethoscope. There basically are 4 types:

• Wheezing Sounds:Especially people with asthma can wheeze from time to time. These sounds are high-pitched and almost sound like someone would have swallowed a chew-toy. If the patient has a really bad asthma problem you can sometimes even hear the wheezing without the need for a stethoscope. This wheezing occurs when the patient exhales.
• Stridor-Sounds: sound similar to wheezing but occur when the patient inhales. This is usually the result of a blockage in the back of the throat. Also, this can be heard at times without the need for a stethoscope.
• Rhonchi Sounds: sound like snoring. You need a stethoscope to detect these sounds. They are caused when air flows through a “rough” patch in the lungs or because the air-pathway in the lungs is blocked.
• Rales Sounds: sound like popping bubble wrap or rattling in the lungs. This is heard when a person inhales.

Lastly Checking Blood Pressure with a Stethoscope:

• You’ll need a “Sphygmomanometer” for this. In simple terms, this just means a blood pressure gauge. On our right-hand side, we can see one. In order to measure the patient’s blood pressure you first need to roll up the sleeve if it’s in the way. If you measure someone’s blood pressure you always need to make sure the blood pressure cuff fits snugly on bare skin.
• Press the bell of the stethoscope over the brachial artery just below the cuff’s edge. You can also use the diaphragm if you have trouble hearing the bell. The sounds to look out for are called “Korotkoff”-sounds. These are low tone knocking sounds that indicate the patient’s systolic blood pressure.
• Next inflate the cuff to 180mmHg or 30mm above your expected systolic blood pressure. You can find the reading by looking at the sphygmomanometer. That’s just a fancy word for the gauge on the blood pressure cuff. Then, release air from the cuff at a moderate rate (3mm/sec).
• As you release the air, listen with the stethoscope and keep your eyes on the sphygmomanometer (gauge on the blood pressure cuff).
• You should hear a knocking sound as air releases from the cuff. Make a mental note the first time you hear such a knocking sound of the reading on your gauge. This will be the patient’s systolic blood pressure. 
• Keep watching the gauge though as the second knocking sound will come just around the corner.
• After this, knocking sound stops, note the number on your gauge when you last heard a knocking sound. This is the patient’s diastolic pressure.
• Lastly, release all the air from the cuff once you noted these two numbers.

Note:

If the systolic pressure is over 120 or diastolic pressure is more than 80, you might want to recheck the patient’s blood pressure once a few minutes have passed. If the second measurement shows again an increased blood pressure it’s time to go see a doctor find out the cause!

👉Please Watch Our Stethoscope Videos (Part 1 & Part 2) from Our YouTube Channel Below:-

1. Part 1 Video:-

2. Part 2 Video :-

Article Prepared By:-

👉 Gaston Ravin Dias 

References:

• The Stethoscope Pros. 2017. Stethoscope: what is it and how is it used? - The Stethoscope Pros. [ONLINE] Available at: http://stethoscopepros.com/stethoscope/. [Accessed 02 November 2017].
• MMM-ext. 2017. Stethoscope History | Littmann Stethoscopes | 3M United States. [ONLINE] Available at: https://www.littmann.com/3M/en_US/littmann-stethoscopes/education-center/history/. [Accessed 02 November 2017].
• MedicineNet. 2017. Medical Definition of Stethoscope. [ONLINE] Available at: https://www.medicinenet.com/script/main/art.asp?articlekey=17896. [Accessed 02 November 2017].
• Stethoscope parts and names. 2017. Stethoscope parts and names. [ONLINE] Available at: http://www.nursetheory.com/stethoscope-parts-and-names/. [Accessed 02 November 2017].
• Best Stethoscope Guide. 2017. Here are 7 Parts of a Stethoscope: And Even I was Surprised | Best Stethoscope Guide. [ONLINE] Available at: https://beststethoscopeguide.com/parts-of-a-stethoscope/. [Accessed 02 November 2017].
• Stethoscope Sound Review. 2017. Parts of a Stethoscope -. [ONLINE] Available at: https://www.stethoscopesoundreview.com/parts-of-a-stethoscope/. [Accessed 02 November 2017].
• Stethoscope Sound Review. 2017. Parts of a Stethoscope -. [ONLINE] Available at: https://www.stethoscopesoundreview.com/parts-of-a-stethoscope/. [Accessed 02 November 2017].
• Best Stethoscope Guide. 2017. How Does a Stethoscope Work? - Best Stethoscope Guide | Best Stethoscope Guide. [ONLINE] Available at: https://beststethoscopeguide.com/how-does-a-stethoscope-work/. [Accessed 02 November 2017].
• Lots More Information - How Stethoscopes Work | HowStuffWorks. 2017. Lots More Information - How Stethoscopes Work | HowStuffWorks. [ONLINE] Available at: https://science.howstuffworks.com/innovation/everyday-innovations/stethoscopes3.htm. [Accessed 02 November 2017].
• Best Stethoscope Guide. 2017. Types of Stethoscopes: What are They? - Best Stethoscope Guide | Best Stethoscope Guide. [ONLINE] Available at: https://beststethoscopeguide.com/types-of-stethoscopes/. [Accessed 02 November 2017].
• What Is A Stethoscope And What Different Types Are There? . 2017. What Is A Stethoscope And What Different Types Are There? . [ONLINE] Available at: http://bloodpressuremonitorguide.com/stethoscope-different-types/. [Accessed 02 November 2017].
• Medisave USA Blog. 2017. How to Choose the Right Littmann Stethoscope (RN, MD, MS). [ONLINE] Available at: https://www.medisave.net/blog/littmann-stethoscope-right/. [Accessed 02 November 2017].