Stethoscope System Research Articles

Design and Implementation of an Integrated Electronic Stethoscope System

Design and Implementation of an Integrated Electronic Stethoscope System

Research on electronic stethoscope system and signal processing algorithm

Stethoscopes have an important role in non-invasive diagnosis of cardiovascular and respiratory diseases, digestive diseases, and other kinds of diseases. The emergence of high-end diagnostic devices and new diagnostic methods have caused the status of the stethoscope to decline. However, stethoscope has the advantages of simple operation, mature auscultation theory and low cost, and thus is still widely used in medical diagnosis. This paper first introduces the design and application of electronic stethoscope solutions based on contact sensors and air coupling sensors, and then introduces advanced algorithms for digital signal processing for the diagnosis and treatment of different diseases, including heart sound noise reduction algorithm, heart sound segmentation algorithm and heart sound feature extraction and recognition algorithm. Finally, this paper summarizes the application of the electronic stethoscope system in medical testing, and its future development direction. In summary, the electronic stethoscope system is a reliable medical testing tool, which can convert sound signals into digital signals through complex signal processing algorithms for more accurate detection of human physiological parameters. The research of this paper will be of great value to the research and application of electronic stethoscopes.

Biocompatible Piezoelectric Polymer Poly(Lactic Acid)-Based Stethoscope for Wearable Health Monitoring Devices

With the development of wearable devices and the Internet of Things (IoT), there is a growing demand for portable and comfortable human health monitoring devices. Because of the advantages of biocompatibility, relatively large piezoelectric coefficients, and nonpyroelectricity, poly(L-lactic acid) (PLLA) polymers have been greatly utilized in the applications of tissue engineering, sensors, and energy harvesting devices. In this investigation, the PLLA film was fabricated for the first time for real-time wearable stethoscope and pulse wave sensor applications. First, the stretched PLLA film was glued onto a Mylar film as the active layer of the PLLA film-based stethoscope (PFS) and pulse sensor device. After the PFS device was measured in a semianechoic chamber, the device showed a sensitivity of –53.4 dB at 1 kHz and it also exhibited a stable frequency response in the range of 100 Hz–4 kHz. In addition, the PFS device showed an output voltage of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 90 mV when measuring the heart rate and pulse signal of an adult volunteer. Furthermore, the PFS device was integrated a portable stethoscope system, which can detect a clear pulse signal and send it to a data collection application designed in a cellphone. The biodegradability, stable frequency response, and temperature stability indicate the great potential of PFS device for wearable human health monitoring devices.

Intelligent Stethoscope System and Diagnosis Platform With Synchronized Heart Sound and Electrocardiogram Signals

Intelligent Stethoscope System and Diagnosis Platform With Synchronized Heart Sound and Electrocardiogram Signals

Coherence Function and Adaptive Noise Cancellation Performance of an Acoustic Sensor System for Use in Detecting Coronary Artery Disease.

Adaptive noise cancellation is a useful linear technique to attenuate unwanted background noise that cannot be removed using traditional frequency-selective filters. Usually, this is due to the signal and noise co-existing in the same frequency band. This paper tests a weighted least mean squares (WLMS) algorithm on a stethoscope system for use in detecting coronary artery disease in the presence of background noise. Each stethoscope is equipped with two microphones: one used to detect heart signals and one used to detect background noise. The WLMS method was used for four different sources of background noise whilst measuring a heartbeat, including a single tone, multiple tones, hospital/clinic noise, and breathing noise. The magnitude-squared coherence between both microphones was unity for the tone scenarios, resulting in complete attenuation. For the other background noise sources, a less-than-unity magnitude-squared coherence resulted in minor and no attenuation. Thus, the coherence function is a tool that can be used to predict the amount of attenuation achievable by linear adaptive noise-cancellation techniques, such as WLMS, as presented in this article.

Stethoscope acoustics

For over 200 years, stethoscopes have been used to diagnose disease by listening to the sounds from the human body. However, the physics of how stethoscopes work remains poorly understood, mainly because their performance depends not only on the stethoscopes themselves, but on the coupled system that forms when the hand of a clinician presses the device against the chest of a patient. We develop an experimental setup that allows us to characterise the effect of each constituent part on the behaviour of the coupled system. By using a suitably instrumented ‘chest phantom’ we are able to quantify the response of stethoscopes in a repeatable manner and account for the effect of the phantom on the response. We provide a theoretical framework for understanding the acoustics of the coupled stethoscope system and propose a low-order lumped-element model that captures the effects of the key design choices. For example, minimising the air cavity volume inside the stethoscope maximises the response, while a stethoscope’s tubing significantly attenuates the response and introduces distorting standing-wave resonances. Using a diaphragm attenuates the response and shifts the resonances to higher frequencies. However, it also allows the air cavity volume to be minimised, which can offset the attenuation. We dispel several misconceptions, such as that the stiffness of diaphragms leads to an amplification of higher frequencies or that the dimensions of the rim and the mass of the chestpiece play no role in stethoscope performance. We hope that this paper will help to optimise the design of stethoscopes.

Heart and Lung Sound Measurement Using an Esophageal Stethoscope with Adaptive Noise Cancellation.

In surgeries where general anesthesia is required, the auscultation of heart and lung sounds is essential to provide information on the patient’s cardiorespiratory system. Heart and lung sounds can be recorded using an esophageal stethoscope; however, there is huge background noise when this device is used in an operating room. In this study, a digital esophageal stethoscope system was designed. A 3D-printed case filled with Polydimethylsiloxane material was designed to hold two electret-type microphones. One of the microphones was placed inside the printed case to collect the heart and lung sound signals coming out from the patient through the esophageal catheter, the other was mounted on the surface of the case to collect the operating room sounds. A developed adaptive noise canceling algorithm was implemented to remove the operating room noise corrupted with the main heart and lung sound signals and the output signal was displayed on software application developed especially for this study. Using the designed case, the noise level of the signal was reduced to some extent, and by adding the adaptive filter, further noise reduction was achieved. The designed system is lightweight and can provide noise-free heart and lung sound signals.

Hemopneumothorax detection through the process of artificial evolution - a feasibility study

BackgroundTension pneumothorax is one of the leading causes of preventable death on the battlefield. Current prehospital diagnosis relies on a subjective clinical impression complemented by a manual thoracic and respiratory examination. These techniques are not fully applicable in field conditions and on the battlefield, where situational and environmental factors may impair clinical capabilities. We aimed to assemble a device able to sample, analyze, and classify the unique acoustic signatures of pneumothorax and hemothorax.MethodsAcoustic data was obtained with simultaneous use of two sensitive digital stethoscopes from the chest wall of an ex-vivo porcine model. Twelve second samples of acoustic data were obtained from the in-house assembled digital stethoscope system during mechanical ventilation. The thoracic cavity was injected with increasing volumes of 200, 400, 600, 800, and 1000 ml of air or saline to simulate pneumothorax and hemothorax, respectively. The data was analyzed using a multi-objective genetic algorithm that was used to develop an optimal mathematical detector through the process of artificial evolution, a cutting-edge approach in the artificial intelligence discipline.ResultsThe in-house assembled dual digital stethoscope system and developed genetic algorithm achieved an accuracy, sensitivity and specificity ranging from 64 to 100%, 63 to 100%, and 63 to 100%, respectively, in classifying acoustic signal as associated with pneumothorax or hemothorax at fluid injection levels of 400 ml or more, and regardless of background noise.ConclusionsWe present a novel, objective device for rapid diagnosis of potentially lethal thoracic injuries. With further optimization, such a device could provide real-time detection and monitoring of pneumothorax and hemothorax in battlefield conditions.

A Real-Time Heart Rate Signal Detection using an Electronic Stethoscope with Labview.

Better accurate stethoscope measurements have been needed to diagnose heart problems earlier, monitor patients, and provide initial clinical data for physicians. This study aims to evaluate an electronic stethoscope for automatic identification of heart rate by monitoring Beats Per Minute (BPM) in real-time. In this work, a new design with a low cost electronic stethoscope is designed and implemented as a simple circuit for a replacement with conventional stethoscopes. This presented a low cost stethoscopes consisting of a preamplifier, low-pass filter, high-pass filter, microcontroller and Bluetooth. This simulation and experimental study was carried out for electronic circuit design testing. The condenser microphone transmited the signal into the signal conditioning circuit, and amplified it from 10 to 30 times. The low- and high- pass filter circuit was with cutoffs of 180 Hz and 50 Hz, respectively. The result shows that the fourth-order Butterworth filter was the best filter, with a gain of 0.707 Volt, -3.01 dB, and 0.782 Volt, -2.137 dB, respectively. The real-time measurements using the system are not significantly different from the manual measurements, with around 2-5%, with a delay of 1.7 to 2 seconds. The results indicated that an electronic stethoscope system could provide suitable information for BPM value and could display heart sound signals.

Improved Detection of Lung Fluid With Standardized Acoustic Stimulation of the Chest.

Accumulation of excess air and water in the lungs leads to breakdown of respiratory function and is a common cause of patient hospitalization. Compact and non-invasive methods to detect the changes in lung fluid accumulation can allow physicians to assess patients’ respiratory conditions. In this paper, an acoustic transducer and a digital stethoscope system are proposed as a targeted solution for this clinical need. Alterations in the structure of the lungs lead to measurable changes which can be used to assess lung pathology. We standardize this procedure by sending a controlled signal through the lungs of six healthy subjects and six patients with lung disease. We extract mel-frequency cepstral coefficients and spectroid audio features, commonly used in classification for music retrieval, to characterize subjects as healthy or diseased. Using the n}{}Kn-nearest neighbors algorithm, we demonstrate 91.7% accuracy in distinguishing between healthy subjects and patients with lung pathology.

Heart sounds analysis via esophageal stethoscope system in beagles

Esophageal stethoscope is less invasive and easy to handling. And it gives a lot of information. The purpose of this study is to investigate the correlation of blood pressure and heart sound as measured by esophageal stethoscope. Four male beagles weighing 10 to 12kg were selected as experimental subjects. After general anesthesia, the esophageal stethoscope was inserted. After connecting the microphone, the heart sounds were visualized and recorded through a self-developed equipment and program. The amplitudes of S1 and S2 were monitored real-time to examine changes as the blood pressure increased and decreased. The relationship between the ratios of S1 to S2 (S1/S2) and changes in blood pressure due to ephedrine was evaluated. The same experiment was performed with different concentration of isoflurane. From S1 and S2 in the inotropics experiment, a high correlation appeared with change in blood pressure in S1. The relationship between S1/S2 and change in blood pressure showed a positive correlation in each experimental subject. In the volatile anesthetics experiment, the heart sounds decreased as MAC increased. Heart sounds were analyzed successfully with the esophageal stethoscope through the self-developed program and equipment. A proportional change in heart sounds was confirmed when blood pressure was changed using inotropics or volatile anesthetics. The esophageal stethoscope can achieve the closest proximity to the heart to hear sounds in a non-invasive manner.

A digital esophageal stethoscope system for monitoring anesthetized patients’ cardiovascular system

Purpose Esophageal stethoscope is a device to measure heart sound or respiratory sound by inserting a catheter into the patients’ esophagus during operation. It is easy to use, noninvasive, and not influenced by ambient noise, but does not provide the quantitative information about cardiovascular system. Thus, in this study, we tried to develop a digital esophageal stethoscope system (DESS) that can be used to monitor the heart sounds of anesthetized patients during operation.

Sound recording and digital phonocardiography of cardiac murmurs in dogs by using a sensor-based electronic stethoscope

The goals of this study were to present a technique of digitalised sound recordings and phonocardiograms (dPCGs), and to analyse its diagnostic capabilities. Heart sounds of 20 dogs were auscultated in vivo (on-line) and recorded with dPCGs by two authors using a Welch Allyn Meditron Stethoscope System. Sound recordings were auscultated off-line and blindly by four different observers having various auscultatory experiences, then listened to while viewing dPCGs. The results were compared to echocardiographic diagnoses. There was a significant agreement (p < 0.001) between on-line and off-line auscultatory findings regarding the four observers, ranging from 45% to 75% (weighted kappa values: 0.72 to 0.87). The best agreement was achieved by Observer 1 having the highest experience. Significant differences (p < 0.05) were found between Observer 1 and Observer 4 (with the lowest experience) in judging the quality of the murmurs during the off-line and blind auscultation. However, there were only minimal differences (95% to 100% agreements) in dPCG analyses among the four observers regarding intensity and quality of the murmurs while simultaneously listening to and viewing the dPCGs. Significant correlations were found between the traditional '0 to 6 scale' and a new '0 to 3 scale' murmur intensity gradings by all observers (correlation coefficients 0.640 to 0.908; p < 0.01 to p < 0.001). Analysis of dPCGs might be a valuable, additional tool helping with the diagnosis of canine cardiac murmurs, especially for those with less cardiological experience.

Selection of wavelet packet measures for insufficiency murmur identification

This paper presents a new analysis method for aortic and mitral insufficiency murmurs using wavelet packet (WP) decomposition. We proposed four diagnostic features including the maximum peak frequency, the position index of the WP coefficient corresponding to the maximum peak frequency, and the ratios of the wavelet energy and entropy information to achieve greater accuracy for detection of heart murmurs. The proposed WP-based insufficiency murmur analysis method was validated by some case studies. We employed a thresholding scheme to discriminate between insufficiency murmurs and control sounds. Three hundred and thirty-two heart sounds with 126 control and 206 murmur cases were acquired from four healthy volunteers and 47 patients who suffered from heart defects. Control sounds were recorded by applying a wireless electric stethoscope system to subjects with no history of other heart complications. Insufficiency murmurs were grouped into two valvular heart defect categories, aortic and mitral. These murmur subjects had no other coexistent valvular defects. The proposed insufficiency murmur detection method yielded a high classification efficiency of 99.78% specificity and 99.43% sensitivity.

Cardiac sound murmurs classification with autoregressive spectral analysis and multi-support vector machine technique

In this paper, a novel cardiac sound spectral analysis method using the normalized autoregressive power spectral density (NAR-PSD) curve with the support vector machine (SVM) technique is proposed for classifying the cardiac sound murmurs. The 489 cardiac sound signals with 196 normal and 293 abnormal sound cases acquired from six healthy volunteers and 34 patients were tested. Normal sound signals were recorded by our self-produced wireless electric stethoscope system where the subjects are selected who have no the history of other heart complications. Abnormal sound signals were grouped into six heart valvular disorders such as the atrial fibrillation, aortic insufficiency, aortic stenosis, mitral regurgitation, mitral stenosis and split sounds. These abnormal subjects were also not included other coexistent heart valvular disorder. Considering the morphological characteristics of the power spectral density of the heart sounds in frequency domain, we propose two important diagnostic features Fmax and Fwidth, which describe the maximum peak of NAR-PSD curve and the frequency width between the crossed points of NAR-PSD curve on a selected threshold value (THV), respectively. Furthermore, a two-dimensional representation on ( Fmax, Fwidth) is introduced. The proposed cardiac sound spectral envelope curve method is validated by some case studies. Then, the SVM technique is employed as a classification tool to identify the cardiac sounds by the extracted diagnostic features. To detect abnormality of heart sound and to discriminate the heart murmurs, the multi-SVM classifiers composed of six SVM modules are considered and designed. A data set was used to validate the classification performances of each multi-SVM module. As a result, the accuracies of six SVM modules used for detection of abnormality and classification of six heart disorders showed 71–98.9% for THVs=10–90% and 81.2–99.6% for THVs=10–50% with respect to each of SVM modules. With the proposed cardiac sound spectral analysis method, the high classification performances were achieved by 99.9% specificity and 99.5% sensitivity in classifying normal and abnormal sounds (heart disorders). Consequently, the proposed method showed relatively very high classification efficiency if the SVM module is designed with considering THV values. And the proposed cardiac sound murmurs classification method with autoregressive spectral analysis and multi-SVM classifiers is validated for the classification of heart valvular disorders.

Development of Wireless Electronic Stethoscope System and Abnormal Cardiac Sound Analysis Method (Sound Characteristic Waveform Analysis)

This paper is concerned with the development of a wireless electric stethoscope system and cardiac sound analytical method for cardiovascular disease diagnosis. This system consists of an electronic stethoscope, data acquiring amplifier/filter circuits, wireless transmitter and receiver modules, and a notebook computer. The cardiac sound acquired by the electronic stethoscope and can be easily transmitted to the computer by wireless transmitter and receiver modules. The input-output characteristics of the electronic stethoscope and wireless modules are investigated in detail. Furthermore, one-DOF analytical model based on the consideration of the eardrum property is proposed for abnormal cardiac sound analysis. With the analytical model the original heart sound signal can be converted to a simple characteristic waveform which fits the behaviors of some cardiovascular diseases. Some case studies using the characteristic waveforms show that the normal sound can be distinguished visually from the abnormal cases such as the mitral regurgitation, aortic incompetence, allorhythmic pulse and so on.

Preadmission anesthesia consultation using telemedicine technology: a pilot study.

TELEMEDICINE has been defined as the delivery of healthcare and sharing of medical knowledge over a distance using telecommunications systems. 1 It uses modern high-speed telecommunication systems that allow interactive video-mediated clinical consultations. Telemedicine enables the delivery of healthcare irrespective of geographic location or ability to travel to tertiary healthcare centers. 2 In Canada, a significant population lives in remote regions away from tertiary care centers. At Toronto Western Hospital, 15% of patients are referred from remote regions. Telemedicine can potentially reduce travel costs and improve accessibility to health care. Although telemedicine has been used by other medical and surgical specialties, there have been no reports in the literature evaluating telemedicine technology for anesthesia consultations. 3-5 We report the technical aspects and implementation of telemedicine anesthesia consultation, the first 10 patients interviewed, and their satisfaction regarding telemedicine consultations.

PC를 기반으로 한 선박용 디지털 심전도 및 청진기 개발

심전도 측정기와 청진기를 통하여 획득된 심전도와 심음도는 비관혈적 방법으로 환자를 진단할 수 있는 생체신호이며, 의사들의 진단도구로 널리 이용되어져 왔다. 그러나 의사들이 심전도 측정기나 청진기를 이용하여 환자를 진단하는 장소는 병원 내 진료실과 응급실로 한정되어 있기 때문에, 병원에서 거리가 먼 원거리 지역이나 자동차, 비행기, 선박에서는 환자의 심음을 확인할 수 없다. 특히, 원양항해에 종사하는 선박 환자는 전문 의료진으로부터 진료를 받을 수 없는 경우가 있다. 본 논문에서는 환자의 심음 및 심전을 용이하게 측정함으로써 PC기반의 선박용 디지털 심전도 및 청진기를 개발하였으며, 해상 원격진료의 출현을 앞 당길 수 있으리라 본다. Electrocardiogram and phonocardiogram acquired from ECG and stethoscope by a non-invasive method are bio-signals which laue been a great role in patients diagnosis and used extensively by doctors. And these are mainly used at the examination room or first-and room of hospital. When the patients are located at some places far away from hospital like a car, an airplane and a vessel under way, there are some difficulties in confirming their cardiac sound Especially the patient of ocean going vessel might not have a medical treatment from the professional doctor at times. In this paper, we developed the digital ECG and stethoscope system based on personal computer which can easily measure the patient's cardiac sound and ECG signal, and this might shorten the appearance of the remote maritime telemedicine.

異常心音診断用デジタル聴診器システムの開発(生体治療・医療, バイオ操作・検査,IIP2004 情報・知能・精密機器部門講演会)

This paper is concerned with the development of a wireless stethoscope system for diagnosis of cardiac disorders. This system consists of an electronic stethoscope, a sound converter circuit, audio wireless transmitter and receiver modules and a computer. The cardiac sound is easily acquired by the electronic stethoscope and transmit to computer by audio wireless modules for abnormal cardiac sound monitoring and diagnosis. A filter with the eardrum mechanical characteristic is designed and characteristic waveforms are obtained by applying the recorded heart sound signals through the filter. Some experimental examples have shown that the characteristic waveforms are powerful to diagnosis the abnormal heart sound and easy operation for the users who even have no special knowledge on the cardiac diagnosis.

Stethoscope system for self-examination using internet

Provided is a stethoscope system for self-examination using the Internet. The stethoscope system includes a member's digital stethoscope for measuring sound waves of a member's body, connecting to a prescribed web address, transmitting the member's current sound wave data, requesting for remote medical examination, and displaying an examination result, a web server for storing the measured current sound wave data received from the member's digital stethoscope in response to the member's request, examining the member's health condition using the measured current sound wave data, the pre-stored disease sound wave data, and the pre-stored normal sound wave data, connecting to the member's digital stethoscope for transmission of the examination result, or transmitting member identification information, details for the request for remote medical examination, the member's current sound wave data and the pre-stored member's normal sound wave data to request a medical specialist for remote medical examination, a remote medical examination system for receiving the member identification information, details for the request for remote medical examination, the member's current sound wave data and the pre-stored member's normal sound wave data from the web server, performing remote medical examination by the medical specialist based on the received data, and transmitting the examination result to the web server by the medical specialist's instruction, and a communication system for connecting the member's digital stethoscope, the web server and the remote medical examination system with one another.