Electronic stethoscopes are becoming more prevalent in medical environments. Electronic stethoscopes have a number of advantages over the traditional acoustic stethoscope. However, just like every new replacement technology, electronic stethoscopes inevitably have some disadvantages. The question now is does the advantages of the electronic stethoscope outweigh the disadvantages? Should you jump on the digital bandwagon or should you cling to your old rugged traditional acoustic stethoscope?
In this article, I will provide you with the important information that you need to know about the electronic stethoscope. I will discuss how an electronic stethoscope works. I will discuss the electronic components that constitute the electronic stethoscope. This will give you insight into what an electronic stethoscope is capable of doing and how the electronic stethoscope works the way it does. I will objectively discuss the advantages and disadvantages of an electronic stethoscope. I will discuss how your practice can benefit from an electronic stethoscope and the baggage that comes with adopting an electronic stethoscope.
I will illustrate my discussion on the electronic stethoscope with examples of commercially-available electronic stethoscopes. Finally, I will conclude with my recommendation on whether you should get an electronic stethoscope or not (spoiler: my conclusion is not what you think)
How does an Electronic Stethoscope Work?
An Electronic Stethoscope uses a sensor (otherwise called a transducer) to convert body sounds to an analog electronic signal. The electronic stethoscope then uses an Analog to Digital Converter (ADC) to convert the analog signal to a digital signal. The electronic stethoscope then uses a Digital Signal Processor (DSP) to filter noise out of the digital signal. The signal is then amplified and transmitted over a wired or wireless link (i.e Bluetooth) to the earpiece of a medical examiner.
In addition to transmitting sound to the ears of the medical examiner, an electronic stethoscope can also transmit the body sound signals to a smartphone or a computer. Software on the smartphone or on the computer can then process the signals with machine-learning algorithms to automatically detect abnormal heart or lung sounds.
Here are the popular electronic stethoscopes :
- Eko CORE Digital Stethoscope
- 3M Littmann Electronic Stethoscope Model 3200
- Thinklabs One Digital Stethoscope
- Cardionics Clinical E-scope
- American Diagnostic Corporation Adscope 658
Although these electronics stethoscopes operate based on the same core principles, each one still has its peculiar features and its working principles. Here, I will discuss in detail electronic stethoscopes in general and how each of these stethoscopes in particular.
Control Buttons on an Electronic Stethoscope
Here are the typical control buttons that you will find on an electronic stethoscope head
- Power Button turns on and off the electronic stethoscope
- Volume Adjustment Button controls the loudness of the sound output of the stethoscope (sets te stethoscopes amplification level)
- Mode Change Button changes the audio frequency range over which the stethoscope is sensitive: bell mode for low-frequency sound, diaphragm mode for high-frequency sound, the wide mode for both low and high-frequency sound.
Advantages of Electronic Stethoscope over Traditional Acoustic Stethoscope
The traditional acoustic stethoscope has been around for more than 200 years, and it has evolved very slowly over these years. The commercial release of the electronic stethoscope in 2000 was a giant leap for stethoscope technology. The electronic stethoscope completely changed the auscultation experience for medical practitioners.
In a 2011 study, researchers compared the 3M Littmann Cardiology III stethoscope (a traditional acoustic stethoscope) to a 3M Littmann electronic stethoscope (Littmann Stethoscope Model 3000). The researchers found that the electronic stethoscope is better for hearting heart and lung sounds.
In addition to the better auscultation performance, electronic stethoscopes are designed to have the following advantages over traditional acoustic stethoscopes:
- Sound Amplification: The electronic stethoscope uses active electronic circuitry to amplify body sounds. This allows medical practitioners to better hear body sounds. Essentially, the electronic stethoscope solves the noise-prone low output sound level that is typical of the traditional acoustic stethoscope.
- Sound Filtering: The electronic stethoscope can be electronically tuned to listen for body sound within an arbitrary frequency range. This allows medical practitioners to focus on body sounds of interest, exclusive of body sounds that are not in the frequency range of interest. On the other hand, medical practitioners had only two broad sound range options with the traditional acoustic stethoscope. The first option is to use the bell side of the stethoscope chestpiece to pick up sounds within a broad low-frequency sound spectrum. The second option is to use the diaphragm side of the chestpiece to pick up sounds within a broad high-frequency sound spectrum. Electronic stethoscopes allow medical practitioners to listen to sound within narrow frequency ranges.
- Noise Cancellation: Most electronic stethoscopes employ noise cancellation technology to automatically eliminate the noise that interferes with auscultation sounds. The noise can be an external noise such as noise from humming equipment in the hospital or internals sounds such as the patient’s bodily movements. Electronic stethoscopes make it possible for healthcare practitioners to clearly hear auscultation sound without being distracted by noise.
- Sound storage: An electronic stethoscope has an onboard memory that allows healthcare practitioners to record body sounds while the stethoscope capture body sounds from a patient. Healthcare practitioners can later replay the body sounds and carefully annotate and analyze the sound. However, with a traditional acoustic stethoscope, if a healthcare practitioner misses a sound, he or she cannot reproduce that sound.
- Data streaming: Electronic stethoscopes can stream auscultation sound data to an external device such as a mobile phone or a computer. Once the auscultation sound data is on a mobile device or on a computer, the auscultation data can then be shared with or streamed to other healthcare practitioners over the phone’s or computer’s internet network interface. This capability makes the electronic stethoscope an enabler for telemedicine.
- Computer-aided Auscualation: Since the electronic stethoscope produces digitized sound, computer software can automatically analyze the digitized sounds that the electronic stethoscopes produce. Some electronic stethoscopes such as the Eko CORE have accessory software packages that use data analytics and machine-learning algorithms to detect irregularities in cardiac and pulmonary sounds. This aids the healthcare professional to make a more accurate and objective diagnosis. In the future, the computer-aided auscultation features of electronic stethoscopes could be a cheaper and portable option, compared to Magnetic Resonance Imaging (MRI) scans or Computer Tomography (CT) scans, for diagnosing heart and lung problems. Electronic stethoscope manufactures are already working on this.
Components of an Electronic Stethoscope
The components of an electronic stethoscope are shown in the figure below:
Sound Sensor/Transducer
The sound sensor/acoustic-to-electric transducer of the electronic stethoscope converts the body sounds into an analog electronic signal. The conversion of mechanical vibration sounds of organs to an electronic signal by a transducer is the most important step in electronic stethoscope design because once the body sounds signal are converted from their mechanical vibration form to an electronic form, the signal can be easily and flexibly processed with electronic technology.
Different electronic stethoscopes use different types of sensors to convert body sounds from mechanical sound vibrations to analog electronic signals. For example, the Thinklabs One Digital Stethoscope uses a capacitive sensor to convert the mechanical vibration of the stethoscope’s diaphragm into electrical signals. In the Thinklabs Stethoscope, a very high voltage is applied between the diaphragm of the stethoscope and another metallic plate behind the diaphragm.
Two separated plates that have a high voltage applied between them is known as an electrical capacitor. A capacitor is characterized by a measurable electrical parameter called capacitance. The electrical capacitance of a two-plate capacitor depends on the distance between the two plates. The Thinklabs One uses capacitance to convert body sounds to electrical signals.
In the Thinklabs One stethoscope, when the diaphragm of the Thinklabs One Stethoscope vibrates due to the acoustic waves from body sounds, the capacitance of the stethoscope changes in sympathy with the vibration of the diaphragm. These capacitance changes are electrically equivalent to the mechanical vibration of the stethoscope’s diaphragm. Hence, the mechanical vibrations of the diaphragm are converted to their electrical analog.
The 3M Littmann Electronic Stethoscope, the ADC Adscope 658 Electronic Stethoscope, and the EKO Wireless Cardiac Sensor use piezoelectric materials to convert mechanical body vibrations to an electrical signal. A piezoelectric material is a special material that produces electric voltages when the piezoelectric material undergo any physical deformation (such as bending or vibration).
One the other hand, the Cardionics E-scope Stethoscope uses a microphone to convert body sounds to electrical signals.
Once the stethoscope sensor converts the body sounds to an analog electronic form, the low-noise preamplifier of the stethoscope amplifies the electronic signal. The analog electronic signal is then converted to a digital signal for further processing.
Analog to Digital Converter (ADC)
The ADC (Analog to Digital Converter not to be confused with American Diagnostic Corporation) of the stethoscope converts the analog electronic signal that the stethoscope’s sensor produces into a digital signal. Once the signal is in digital form, the stethoscope’s digital subsystem will be able to use powerful digital processing techniques to improve the quality of the signal.
Digital Signal Processor (DSP)
The Digital Signal Processor of the electronic stethoscope performs operations such as noise cancellation and noise filtering on the digital signal. The DSP also filters out sound frequencies that are not in the cardiac or pulmonary frequency ranges of interest. The DSP can also tune the stethoscope to pick up sound with a specific narrow frequency.
The ability of a stethoscope to use its DSP to focus on sound in a specific frequency range is a very vital feature of the digital stethoscope. Sound ranges of auscultation interests are cardiac sound in the 20Hz to 400Hz range and pulmonary sound in the 100Hz to 1200Hz range. Other sound ranges should be blocked off, as they constitute noise. Electronic stethoscopes allow medical practitioners to focus solely on the pathologically relevant sound frequency ranges, exclusive of non-relevant sound frequencies (noise).
Besides, electronic stethoscopes give medical professionals the flexibility to focus on arbitrary narrow frequency ranges. For example, if a healthcare practitioner decides to listen to sounds only in the 50 Hz to 250 Hz range, he or she can easily tune his or her electronic stethoscope to pick up only these sounds.
Body Sound Recording/Playback
Electronic stethoscopes have onboard memories that allow medical professionals to store auscultation sounds on the stethoscope for later playback.
These stored digital body sounds can later be transferred over a computer network and shared with other physicians or the sounds can be saved in an Electronic Health Record (EHR) system.
Digital to Analog Converter (DAC)
After DSP finishes processing the digital signal body sound, the Digital to Analog Converter of the electronic stethoscope converts the digital signal back to an analog signal. The stethoscope then amplifies the analog signal and then routes this analog signal to the earpieces or to a loudspeaker where the signal is converted to an audible sound.
Interface for Connecting to Wireless Headphone/ Smartphone/ Computer
The stethoscope can also route the digital signal from the DSP to a wireless headphone, a smartphone, or to a personal computer where the signal is further processed. The route of the signal can be a wired link (such as a USB cable, a 3.5 mm audio jack cable) or a wireless link such as Bluetooth.
Bluetooth is the wireless technology that stethoscopes use to route signals from the stethoscope to a wireless earpiece/headphone. The ability to use a wireless headphone to listen to auscultation sounds without a direct connection between the patient and the healthcare practitioner is one of the practically distinctive features of the electronic stethoscope vis a vis the traditional acoustic stethoscope. This gives the physician the ability to listen to a patient’s body sound without a physical connection to the patient. This remote auscultation, courtesy the electronic stethoscope, takes to the ultimate level the idea of Rene Lanane, who invented the stethoscope as a means for doctors to examine patients while maintaining a safe distance.
The Eko CORE Electronic stethoscope and the Thinklabs One Electronic stethoscopes (with a Bluetooth transmitter accessory) are two of the electronic stethoscopes that allow medical examiners to wirelessly listen to auscultation sounds with a wireless headset.
On the other hand, the 3M Littmann Electronic Stethoscope Model 3200, Cardionics Clinical E-scope, and the American Diagnostic Corporation Adscope 658 need a wired connection between the stethoscope head and the earpieces.
Bluetooth technology is also used in electronic stethoscopes to transfer auscultation signals from the stethoscope’s head to a smartphone or a computer. The Eko Electronic stethoscope, the Thinklabs One Electronic stethoscopes, and the 3M Littmann Electronic Stethoscope Model 3200 can transfer data from the stethoscope to a smartphone or a computer via Bluetooth.
Once the auscultation sounds are transferred to a smartphone or a computer, they can be streamed over a cellular network or an internet network to any remote location with cellular or internet access. Thus, electronic stethoscopes can be used for telemedicine.
Automated Auscultation Analysis
The software that comes with some electronic stethoscope can analyze auscultation sounds and identify anomalies (see the Eko CORE AI software). This is one of the remarkable capabilities of the electronic stethoscope.
Power Source
Unlike traditional acoustic stethoscopes, electronic stethoscopes require a power source to power their internal electronics. Some electronic stethoscopes are powered with a Lithium-Ion rechargeable battery, some are powered with replaceable AAA or AA batteries. Furthermore, some electronic stethoscopes have the option to be powered with a USB cable, in addition to the option to be powered by batteries.
Electronic Stethoscopes use power management techniques to ensure that the battery of the stethoscope is used efficiently. For example, the electronic stethoscope may turn off itself automatically after the stethoscope has been in an idle state for a while.
However, some electronic stethoscopes can still be used to auscultate when powered off, without a battery, or an external power source. For example, when the Eko CORE Electronic Stethoscope is powered off, it acts like a traditional acoustic stethoscope in the sense that it does not provide amplification of body sounds or other digital electronic functions that are typical of electronic stethoscopes.
How to Convert your Traditional Acoustic Stethoscope to an Electronic Stethoscope
The Eko CORE Digital Attachment allows you to convert your familiar traditional acoustic stethoscope to an electronic stethoscope with all the earlier mentioned capabilities of an electronic stethoscope.
The Eko CORE digital attachment is compatible with the 3M Littmann Cardiology II/III/IV, WelchAllyn Harvey Elite, Medline, and ADC analog stethoscopes.
Cons of the Electronic Stethoscopes
- Price: Electronic stethoscopes are more expensive compared to traditional acoustic stethoscopes. Software with AI capabilities, such as Eko’s AI software that detects heart murmurs and atrial fibrillation, is sold separately from the electronic stethoscope. This adds to the cost of the electronic stethoscope.
- Electronic stethoscopes are not as robust as traditional acoustic stethoscopes. Electronic stethoscopes cannot withstand physical abuse as the traditional stethoscope.
- Because electronic stethoscopes use wireless technology for wireless sound transmission, electronic stethoscopes can be affected by wireless interference of other wireless transmitters if electronic stethoscopes are used near other wireless equipment. Electronic stethoscopes may also interfere with other electronic equipment. Also, the electronic components inside electronic stethoscopes can be affected by the emission from other electronic components. Interference can make an electronic stethoscope to produce weird sounds during auscultation. Therefore, it is important to ensure that the electronic stethoscope is not used near equipment with strong electrical radiation.
- The automatic diagnosis of cardiopulmonary problems with electronic stethoscopes is still a work in progress. The physician’s judgment is still required to make an official diagnosis.
- The batteries in electronic stethoscopes require occasional replacement or recharging.
Conclusion
In conclusion, a modern healthcare practitioner needs an electronic stethoscope in his or her arsenal to take advantage of technological innovation in auscultation. Electronic stethoscopes amplify internal organ sounds making it easy for the modern healthcare practitioner to clearly hear very faint body sounds that could be a symptom of a medical condition.
Also, electronic stethoscopes allow medical practitioners to record auscultation sounds for later careful analysis to get a deeper insight into your patient’s pathology. Furthermore, electronic stethoscopes allow medical practitioners to use computer software together with the healthcare practitioner’s experience to diagnose medical conditions based on a patient’s auscultation sounds. Moreover, electronic stethoscopes allow auscultation data to be streamed from a stethoscope to a mobile phone and then over the internet to remote healthcare practitioners. This allows the electronic stethoscope to be used for telemedicine.
As a medical practitioner, an electronic stethoscope will help you in making your diagnosis. Mastery of the use of the electronic stethoscope is a very valuable skill to learn because electronic stethoscope will become more common in medical environments in the near future, and you will be expected to be able to use one.
The table below is a comparison of the electronic stethoscopes discussed in this post.
|
Electronic Stethoscope |
Sensor Type |
Max Amplification |
Has Bluetooth? |
Power Source |
Active Noise Cancellation |
Weight | Price |
|
N/A |
30x |
No |
Single AAA battery |
No |
176 g |
$335.00 | |
|
Piezoelectric |
18x |
No |
Rechargeable Lithium-Ion battery |
No |
175 g |
$239.99 | |
|
Piezoelectric |
24x |
Yes |
Single AA battery |
Yes |
185 g |
$389.99 | |
|
Piezoelectric |
40x |
Yes |
Rechargeable Lithium-Ion battery |
Yes |
204 g |
$249 | |
|
Capacitive |
100x | Yes (need to purchase Bluetooth adapter separately) |
Rechargeable Lithium-Ion battery |
No |
50 g |
$499 |
Do you have any thoughts on the electronics stethoscope that you will like to share with me? Kindly leave me your comments below.
Additional References
- MaximIntegrated
- The electronic stethoscope
- Electronic Stethoscope Comparison Table by Eko Health
- Electronic Stethsocope Comparison by American Diagnostic Corporation