Different Types of Stethoscopes
Stethoscopes are often a symbol of healthcare professionals as they are useful especially in the medical field, for instance, when working in a nursing home.
A stethoscope is used to listen to the internal sounds of a patient such as the heartbeat, lung sounds, intestines, and blood flow in veins and arteries.
When combined with a sphygmomanometer, it can be used to measure blood pressure.
History of Stethoscope
Stethoscopes date back to 1816, where Rene Laennec from France invented the first stethoscope in Paris at the Necker-Enfants Malades Hospital.
The invention came as a result of Laennec needing a device that would enable him to listen to the heartbeat of women patients without having to lean on their chests. He discovered that a rolled piece of paper from the patient’s chest to his ear would amplify sounds from the heart.
The device was made of a wooden tube and resembled an ear trumpet. Laennec called it a stethoscope, i.e. “Chest scope” and said it was used in “mediate auscultation,” an intermediary device (between heart and chest) used for listening (auscultation). It was monaural.
More stethoscope makes came up from then. In 1829, a flexible binaural stethoscope was made. The stethoscope was clearly described by Golding Bird in 1840. It had a single earpiece.
In 1851, Arthur Learned, a physician from Iris invented a binaural. The stethoscope which was perfected by George Phillip in 1852 had two earpieces and thus became the standard design since.
In 1858, Somerville Scott Alison described his stethophone invention at the Royal Society. It had two separate bells, allowing the hearing and comparison of sounds from two different locations.
His invention marked a major step in the redefinition of disease by encouraging further definitive studies, which led to the advanced knowledge in the localization of sound and binaural fusion. The disease could therefore be detected from the anatomy even though there were no visible symptoms.
In the 1940s, Rappaport and Sprague designed a new stethoscope consisting of two sides, one for the respiratory system and the other for the cardiovascular system. The design was made by Hewlett-Packard. The rappaport-sprague stethoscope was short and heavy.
In the 1960s, a lighter model with improved acoustics was created by David Littmann. He also introduced the tunable diaphragm in the late 1970s with features that could increase the volume of low-frequency sounds among other benefits.
In 1999, DRG Puretone, the first external noise-reducing stethoscope was patented by Richard Deslauriers. The patent was later acquired in 2005 by Trimline Medical Products.
Types of Stethoscopes
When viewed physically, stethoscopes may look similar, but they come in different types, categorized according to technology (acoustic and electric), age, e.g. pediatric and adults, and purpose, for example, the cardiology and recording stethoscopes. The different types of stethoscopes and their uses are described below;
- Acoustic Stethoscope
An acoustic stethoscope is unpowered and has three main components that aid its functions. These are the chest piece, tubing, and earpieces.
- The chest piece consists of a bell which transmits low-frequency sounds, and a diaphragm which transmits high-frequency sounds.
- The tubing is an air-filled hollow tubing that transmits chest sounds to the listener.
- The earpiece allows the listener to hear the chest sounds. How the ear tip is placed on the ear will determine the sound quality, as there should be no air break or leak in the circuitry.
- Cardiology Stethoscope
The cardiology stethoscope is specially designed for use by specialists in the cardiovascular medicine field, for listening to sounds produced in the cardiovascular system such as valve activity and heartbeat. It can also be used as a regular telescope. Its features include:
– It can give quality acoustic and can hear high and low frequencies without using a bell.
– Its earpieces are thick, reducing distractions from external noises.
– It has thicker tubing and reduced distance between the earpiece and diaphragm, which helps to maintain a high quality of sound and promote sound amplification.
– The diaphragm made of hardened plastic or stainless steel which makes it more receptive and sensitive to heart vibrations. It has a rubber or plastic rim reinforcement to enhance patient comfort.
– Some come with pressure tunable diaphragm acting as a diaphragm and bell on the same side, allowing for adjusting of pressure applied to the chest piece in order to listen to different frequencies of sound.
– The thick tubing and steel chest makes them slightly heavier.
- Infant Stethoscope
It is used on infant patients and comes with a smaller diameter of around 2.6 cm. The infant stethoscope gives accurate auscultations for infants. To avoid allergic reactions in infants, it has a non-latex build up.
- Pediatric Stethoscope
The pediatric stethoscope also has a medium-sized chest piece, and it comes with a color resembling a toy and can. It is therefore, suitable for use on frightened children and children in general.
- Electronic Stethoscope
The electronic stethoscope, also known as a stethophone, electronically amplifies the sounds obtained from the chest piece and converts it into electric waves that are transmitted via particular circuits and processed for better auscultation.
Current technologies that are preferred include piezoelectric crystals and diaphragms with an electrically conductive inner surface.
They come in two categories, the digitizing stethoscope which converts audio sounds to a digital signal, and the amplifying stethoscopes which simply and amplify sounds. Its features include;
- Amplification of cardiac and respiratory sounds, hence speeding up diagnosis.
- One can put filters that select cardiac and pulmonary sounds.
- Real-time recording of auscultation.
- Auscultation sharing with other professionals.
- Listening to live auscultation simultaneously.
- Can be used to view the phonocardiogram.
- Chest piece can be exchanged for neonatal, pediatric, and adult use.
- Teaching Stethoscope
The teaching stethoscope is mainly used for teaching purposes. Its other features include;
- A dual headset which enables the teacher and the student to use it at the same time.
- A solid stainless chest piece.
- Highly durable single-lumen tubing.
- Recording Stethoscope
A recording stethoscope is a type of an electronic stethoscope that can be used to record auscultations obtained from a patient in real-time. This is done by connecting the stethophone to a recording device.
Doctors mostly record unfamiliar sounds in order to hold consultations with other doctors and determine the case at hand.
Acoustic vs. Electronic Stethoscope
The electric stethoscope differs in many functional ways from the traditional acoustic stethoscope. The table below outlines their striking differences;
|Acoustic Stethoscope||Electronic Stethoscope|
|Has a simple mechanical construction with the sound being transmitted from the chest piece through a hollow tube to the ears of the listener.||Its chest piece is a contact microphone that converts vibrations into electric signals which are amplified, filtered and fed into a headphone or speaker.|
|Sounds transmitted are less audible, subtle and difficult to distinguish, and hence diagnosis will depend on the level of hearing as well as the experience of the physician. Interchanging between the use of bell for low-frequency sounds and diaphragm for high-frequency sounds may help the issue.||It amplifies quiet sounds. However, it is prone to electric and ambient noises which can be corrected by use of filters.|
|It is recommended and preferred as it is easy to use.||It is not the best for individuals who are starting out in the medical field, those who do not have hearing issues, and those not working in specialised fields such as those focusing on heart and lung length.|
|It is cheaper and lighter.||It is heavier and more expensive.|
Always buy a stethoscope that will best fit the function you intend to put it into. The material quality is also an important consideration.
The most recommended stethoscope for use when working in a nursing home, for instance, is the Ultrascope Single Cardiology stethoscope which is priced in the range of a standard stethoscope, has varied functionality, and is also of high quality.