Stethoscope Parts, Uses and Its Functions

Stethoscope Parts and Its Functions
Stethoscope Parts and Its Functions

Definition of Stethoscope?

The Stethoscope is an acoustic device (mostly a mechanical device, Electronic Stethoscope are new inventions however have not been marketed and are not in use as the mechanical stethoscopes) which enables the users, Medical Practitioner to hear bodily sounds of different frequencies thus helps in diagnosis and monitoring of different health conditions and diseases of animal and humans. Other than medical stethoscopes there are also other types of non-medical stethoscopes commonly called the Mechanic’s stethoscope which are used to listen to internal sounds made by different types of machines and are used in the diagnosis of malfunction of automobile engines in the automobile industry.

A medical stethoscope is an important diagnostic tool for every clinician, other health workers like the paramedics and Nurses who use it to diagnose and monitor the disease conditions based on the changes in the character of the sounds heard in different disease conditions, In addition to its staunch utility in the Medical diagnostics, it is often a symbol of recognition of Health workers, particularly doctors and nurses and is worn as an ornament in its most superlative and optimum position around the neck of the above-mentioned dignitaries of the Medical field. A 2012 research paper published in the Journal of Medical Internet Research 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.

Definition or Meaning of Auscultation

Etymologically “Auscultation” is derived from the Latin word “Auscultatio” meaning “Listen attentively to”. The Medical sense was added to the word later in 1821 as “Listening to the internal parts of the organ via a stethoscope” after the discovery of stethoscopes by Laennec in 1816 AD. Based on the medical knowledge of the present contest, Auscultation refers to the technique performed by the health care professionals during the examination of the patient so that the sound which is heard enables one to diagnose and monitor the disease conditions. 

What’s the history of stethoscopes from the beginning till today?

S.N Name of Inventors Area of Invention Year
1. Rene Laennec Invented First Stethoscope 1816
2. Priorry Invented Funnel shaped bell, a lightweight stem, and fine earpiece 1828
3. Williams Invented First Binaural Stethoscope 1843
4. Marsh Effective Chest Piece of Stethoscope 1851
5. Cammann Developed Flexible Tubing 1855
6. Bianchi Developed Rigid diaphragm, “phonendoscope” 1894
7. Bowles and Sprague Combined bell and a rigid diaphragm 1925
8. Rappaport, Sprague and Groom Combined chest piece, short tubing with low internal volume and well fitting earpieces. 1945–1946
9. Littman Onwards Modern Stethoscope 1956

The history of the stethoscope dates back to 1816 AD when it was invented by Rene Laennec at the Necker-Enfants Malades Hospital in Paris. The first of its kind this stethoscope consisted of a wooden tube and was monaural. Laennec invented the stethoscope because he was not comfortable placing his heart directly onto a woman’s chest to listen to her heart for which in one of the early examinations, he used the rolled paper for auscultation thus deriving his knowledge that even a rolled paper can transmit sound. Laennec called his invention the stethoscope” and attributed its use to hearing different body sounds. This stethoscope was like the hearing aid used during that time, the so-called ear trumpet.

Although there are reports of the binaural stethoscopes that are invented in 1829 and 1840 by Golding Bird, it was not until 1851 that the major modification in the stethoscope was introduced by Irish Physician Arthur Learned when he invented the Biaural instrument and demonstrated its use, In 1852 George Cammann further refined and perfected the design of the instrument and started the commercialization of the device for further use. Cammann also wrote a major treatise on diagnosis by auscultation, which the refined binaural stethoscopes made possible. There were also reports of differential stethoscopes that were introduced around the year 1873 creating a slight stereo effect but they were not used extensively for Clinical purposes. In 1894 it was Dr. Robert Bowles who combined the diaphragm with the bell of the stethoscope. This combination stethoscope remains the basis of those still used today.

Several other minor modifications were made in the stethoscopes in the following years until in the early 1960s when David Littmann a HARVARD Medical School Professor and renowned cardiologist presented a revolutionary new stethoscope with vastly improved acoustical performance. 3M acquired Dr. Littmann’s stethoscope business a few years later and continued to refine the product with explicit designs and enhanced acoustic experience.

When the first stethoscope was needed and by whom and under what circumstances.

Although there are several versions to the story about how the first stethoscope came into existence, the most plausible explanation is the fact that it was invented by Rene Theophile Hyacinthe Laennec during his times at Necker-Enfants Malades Hospital in Paris when he was not comfortable with the direct examination of the women’s chest. To be more specific there has been mention of an obese young woman with “general symptoms of a diseased heart”. He used a paper to keep a distance between the patient’s chest and his ear. To his surprise, the rolled paper not only conducted the sounds but also amplified them and it was based on this observation that he invented the stethoscope initially as a wooden tube.

What are the different parts of the stethoscope?

Different parts of the stethoscopes are:

S.N Parts Of Stethoscope Descritpion
1. Ear Tips Plastic or Silicone buds at the top of the stethoscope that rest in the ear.
2. Ear Tubes Metal pieces that connect the earpieces to the tubing of the stethoscope.
3. Tubing’s Tube connecting the Chest piece with the Ear tubes for the conduction of the sound waves.
4. Chest Piece Known as Head of the stethoscope and consists of 3 parts.
5. Stem Connection between the chest piece and the Tube of the stethoscope.
6. Diaphragm Major Sound conducting part of the stethoscope
7. Bell Used for hearing sounds of lower frequency.

1. Ear Tips: Ear tips are the plastic or silicone buds at the top of the stethoscope that rest in the ear. Most Stethoscopes come with two or three different sizes of ear tips. The ill-fitting ear tips may affect the transmission of the sounds as well as the comfort with which the auscultation is done.

2. Ear tubes: These are the metal pieces that connect the earpieces to the tubing of the stethoscope which is responsible for holding the ear tips.

3. Tubing’s: It is a tube connecting the Chest piece with the Ear tubes and is responsible for the efficient conduction of the sound waves. There are two types of Stethoscopes depending on the number of tubings connecting the chest piece with the Ear tubes. They are Single and double-lumen tubes. When choosing a stethoscope it is necessary to choose one with a thicker tube as the thinner may allow the outside sound to pass through thereby decreasing the quality of the sound that is heard. Though most the stethoscope tube come at a tube length ranging from 25-35 cm, Length is an important part of a stethoscope tube where care should be taken while selecting, the shorter length may make auscultation difficult from a comfortable distance and long tube length obscures the quality of the sound that is heard. 

4. Chest Piece: Also Called the Head of the Stethoscope. Consists of 3 parts:

A. Stem: Acts as a connection between the chest piece and the Tube of the stethoscope. In the case of stethoscopes with a bell and a diaphragm, it is the metallic area that enables one to rotate the head of the stethoscope and alternate between the use of a bell and a diaphragm.

B. Diaphragm: It is the main sound conducting part of the stethoscope, The diaphragm of different stethoscopes varies in the degree of efficient sound conduction through the body via the tubes into the ear tips. The auto-tunable diaphragm of Littman Stethoscopes like the master cardiology, Cardiology S.T.C allows sounds of different frequencies to be heard by only changing the pressure that is applied over the chest and not switching on to the bell mode.

C. Bell: It is smaller in size as compared to the Diaphragm and is used for hearing sounds of lower frequency. Because of its small size, it is also used to listen to the breath sounds of smaller pediatric patients.

What’s the difference between diaphragm and bell?

S.N Diaphragm Bell
1. Diaphragm is responsible for the conduction of high-frequency sounds Bell is responsible for the conduction of the low-frequency sounds.

The diaphragm is responsible for the conduction of high-frequency sounds while the bell is responsible for the conduction of the low-frequency sounds.

How does a stethoscope work?

The use of the stethoscope is based on the principle of sound transmission through a tube with both ends closed. When the closed end of the bell is placed over the body of the individual the vibrations coming out of the bodily sounds are picked up by the diaphragm and sends it through air-filled hollow tubes to the earpiece for listeners to then hear. Similarly, when the open bell is placed over the skin of the individual it is the skin of the patient itself which picks up the vibration, acts as the diaphragm, and transmits the sound waves via the air in the tubings to the earpiece to hear.

Can a doctor detect holes in the heart by using just stethoscopes?

Yes, there are different instances when an examining Doctor can detect different medical conditions of the heart based on the findings of the auscultation of the heart. Different heart conditions like Atrial Septal Defect, Ventricular Septal Defect, and Patent Foramen Ovale are characterized by heart defects (In the language of the Lay Person so-called the Holes in the heart). For an experienced Clinician, it is possible to detect the aforementioned Clinical conditions based on the observations while auscultation. The different types of murmurs that are heard in different heart conditions will enable the physicians to diagnose a particular condition. An account of the exact size, dimension, and its effect on the overall function of the heart, however, needs a proper Echocardiogram of the heart which helps in reaching a diagnostic goal, nevertheless, a Stethoscope helps in the early detection of the Holes if you have any.

Why students should buy Littman Stethoscope? Top ten legit points.

Students should preferably buy Littman Stethoscope because of the following reasons:

S.N Features Description
1. Dual Lumen Tubing Has two separate lumens for extra acoustic touch to these stethoscopes.
2. Comfortable Ear tips Acoustic seal that allows only desired sounds to be heard.
1. Anatomically designed Headset For maximum Sound transfer and a better acoustic experience.
1. Warranty Littmann stethoscopes come with different years of warranty depending on their types.
1. Non-Allergic Not made up of Natural rubber which suits both the examiner and the patient allergic to the natural rubber latex.
1. Chest Piece Made up of a non-chill rim which adds to the patient comfort.
1. Brand One of the best brand in the world.
1. Acoustic Experience Provide a high level of acoustic experience to the clinicians.
1. Tunable Diaphragm More efficient by eliminating the need to remove, turnover, and reposition the chest piece to hear different frequency ranges.
1. Quality Good durability and are resistant to wear and tear as compared to the other stethoscopes.

1) Dual Lumen Tubing: The tubing that connects the Chest diaphragm with the earpiece has two separate lumens for each ear which in addition to preventing the rubbing sounds provides an extra acoustic touch to these stethoscopes.

 2) Comfortable Ear tips and snap-tight soft-sealing Ear tips: The snap-tight soft-sealing ear tips provide an excellent acoustic seal that allows only desired sounds to be heard.

3) The anatomically designed Headset is angled to fit the Ear Canal for maximum Sound transfer and a better acoustic experience. Also, the tension of the headset can be easily adjusted as per need.

4) Warranty: The 3M Littmann stethoscopes come with different years of warranty depending on their types.

5) Non-Allergic: The tubing of the Littmann stethoscopes is not made up of Natural rubber which suits both the examiner and the patient allergic to the natural rubber latex.

6) Chest Piece: The chest pieces of the Littmann Stethoscopes are made up of a non-chill rim which adds to the patient comfort and provides a good interface of care between the patient and the caregiver.

7) Brand: Littmann stethoscopes are not only stethoscoped, in addition to the highest level of diagnostic significance these instruments possess, it is also a brand and the prospects one looks upon a fellow Doctor carrying Littman is a whole new story.

 8) Acoustic Experience: These stethoscopes provide a high level of acoustic experience to the clinicians and are rated high for acoustic performance and boost up the confidence of the user.

9) Tunable Diaphragm: The tunable diaphragm of the Littmann stethoscopes makes auscultation more efficient by eliminating the need to remove, turnover, and reposition the chest piece to hear different frequency ranges.

10) The Littmann Stethoscopes have very good durability and are resistant to wear and tear as compared to the other stethoscopes.

Can a doctor detect problems in the heart’s and lungs using a stethoscope?

Yes, the stethoscopes help to amplify the bodily sounds that are normally not heard bare ear. Different disease conditions of the Lungs cause the normal vesicular breath sounds to be replaced by the abnormal lung sounds for example if a patient is suffering from pneumonia with the consolidation of the lungs, then the type of lung sounds heard over the area of the consolidation is different from the corresponding area of the lungs which may be normal, similarly, the sounds coming from the lungs of the individuals of the Interstitial Lung Disease have crackles so-called the Velcro Crackles ( corresponding to the sounds of the Velcro). Similarly, Wheezes are heard in individuals with Bronchial Asthma, and basal crepitations in the lungs in patients who developed Pulmonary edema secondary to Heart failure (The Left Ventricular Failure). 

Similarly, a variety of Heart conditions can be detected from the character of the Heart sounds and the murmurs that are heard. Therefore, it can be extrapolated that Stethoscopes are a wonderful acoustic device that helps detect a myriad of heart and lung conditions provided the Clinician has the expertise to evaluate the findings.

What are the uses of stethoscopes?

1) Measuring Blood pressure : 

The stethoscope is used to hear the Korotkoff sound, which in turn helps in the evaluation of the blood pressure in the individuals. There are a total of 5 phases of Korotkoff sounds, The first phase of Korotkoff sound corresponds to the Systolic Blood Pressure and the 5th phase of Korotkoff sound corresponds to the Diastolic Blood pressure. This phase actually corresponds to the disappearance of the sound. In some individuals like the AV Fistula, the Korotkoff sound doesn’t disappear at all,so in these individuals, the muffled sound corresponds to the DBP and not the disappearance of the sound. To distinguish between the different types of the Korotkoff sounds it is imperative that the individual have a good quality stethoscope in hand.

2) Assessing heart sounds:

Normal Heart sounds, as well as abnormal heart sounds, are evaluated and examined in the 5 cardiac Auscultatory areas. They are the Aortic, Pulmonic, Mitral, Tricuspid, and Erb’s Point. Normally there are two heart sounds, S1: Due to the Closure of the Atrio- Ventricular valves (Mitral and Tricuspid Valve), S2( Due to the Closure of the Aortic and Pulmonic Valves), There may be physiological 3rd heart sounds in children’s and in Pregnancy and some functional murmurs in the individuals which are non-pathological. Except for these sounds, all the other sounds that are heard in the cardiac areas of auscultation are pathological and point to some of the other disease conditions.

3) Assessing lung sounds.

The chest is auscultated in the Supraclavicular, Infra-clavicular, Mammary, Axillary, Infra-axillary, Interscapular, and Infra-scapular areas to give the clinical picture of the entire lung fields. The abnormal sounds heard in the lungs may be specific to a particular lung field in a localized disease condition or may be distributed over the entire lung field in case of disseminated and systemic conditions. Eg, COPD, Asthma, Infective etiology like pneumonia, and Rheumatological conditions like Sarcoidosis may affect both the lungs while localized pleural effusion and lung infarctions may affect a particular lung field, and henceforth the findings of auscultation may be localized to that field.

4) Assessing bowel sounds

Normally for the clinical examination of the Abdomen and the alimentary system per se, the bowel sounds are heard in the Right Iliac fossa, the average normal being 3 vowel sound per minute (Range 2-4/ Min, SRB’s Text Book Of Surgery). The frequency of bowel sounds is increased in the settings of the Hyperperistalsis arising out of the acute/subacute Bowel obstruction due to any cause, electrolyte abnormality in Hypercalcemia so-called the classical Abdominal groans. Initially following the distal obstruction of the bowel loops there is reactionary hyperperistalsis of the proximal segments of the bowel resulting in increased frequency of the sounds later when there is fatigue of the bowel musculature there is Ileus with no bowel sounds that could be heard. The metallic bowel sounds are also heard in the settings of the bowel obstruction in the initial stage. Bowel sounds are also decreased in frequency and maybe even absent in cases of Hypokalemia.

5) Detecting bruits

Bruit is an audible vascular sound associated with turbulent blood flow in a partially occluded artery and resembles the murmurs of the heart. A carotid bruit is one such example of the sound which is heard in the setting of turbulent nonlaminar blood flow through the stenotic area. This stenosis in the setting of the carotid artery may be secondary to the Carotid atherosclerotic plaques which occlude the artery in different degrees and severity. Similarly, Abdominal bruit is heard in the midline of the abdomen in the area over the Abdominal aorta in the settings of the Atherosclerosis affecting the Abdominal Aorta, also described in the settings of the Renal Artery. Careful Auscultation with Stethoscopes helps to detect such pathologies and help patient get the treatment early.

6) Measuring the span of liver

Although not widely in practice, the liver span can be measured with the help of what is called the Liver scratch test, wherein medical professionals during a physical exam use a type of auscultatory percussion that uses the difference in sound transmission between solid and hollow organs in the abdominal cavity to locate the inferior edge of the liver. 

This test is most commonly performed by placing the diaphragm of the stethoscope below the Xiphoid process of the sternum and lightly scratching the skin parallel to the expected liver edge. The examiner begins scratching in the right lower quadrant of the abdomen along the midclavicular line and moves superiorly until the sound abruptly increases in volume. This location of suddenly increased auscultation volume is marked as the inferior edge of the liver and can then be used to determine the overall liver size.

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