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The urgent need for telemedicine has become clear in the COVID-19 pandemic. To facilitate telemedicine, the development and improvement of remote examination systems are required. A system combining an electronic stethoscope and Bluetooth connectivity is a promising option for remote auscultation in clinics and hospitals. However, the utility of such systems remains unknown.
This study was conducted to assess the utility of real-time auscultation using a Bluetooth-connected electronic stethoscope compared to that of classical auscultation, using lung and cardiology patient simulators.
This was an open-label, randomized controlled trial including senior residents and faculty in the department of general internal medicine of a university hospital. The only exclusion criterion was a refusal to participate. This study consisted of 2 parts: lung auscultation and cardiac auscultation. Each part contained a tutorial session and a test session. All participants attended a tutorial session, in which they listened to 15 sounds on the simulator using a classic stethoscope and were told the correct classification. Thereafter, participants were randomly assigned to either the real-time remote auscultation group (intervention group) or the classical auscultation group (control group) for test sessions. In the test sessions, participants had to classify a series of 10 lung sounds and 10 cardiac sounds, depending on the study part. The intervention group listened to the sounds remotely using the electronic stethoscope, a Bluetooth transmitter, and a wireless, noise-canceling, stereo headset. The control group listened to the sounds directly using a traditional stethoscope. The primary outcome was the test score, and the secondary outcomes were the rates of correct answers for each sound.
In total, 20 participants were included. There were no differences in age, sex, and years from graduation between the 2 groups in each part. The overall test score of lung auscultation in the intervention group (80/110, 72.7%) was not different from that in the control group (71/90, 78.9%;
The utility of a real-time remote auscultation system using a Bluetooth-connected electronic stethoscope was comparable to that of direct auscultation using a classic stethoscope, except for classification of pleural friction rubs. This means that most of the real world’s essential cardiopulmonary sounds could be classified by a real-time remote auscultation system using a Bluetooth-connected electronic stethoscope.
UMIN-CTR UMIN000040828; https://tinyurl.com/r24j2p6s and UMIN-CTR UMIN000041601; https://tinyurl.com/bsax3j5f
Since the French physician René Laennec invented the stethoscope in 1816 [
However, auscultation became challenging during the COVID-19 pandemic. As medical staff also need to be protected from infection during an outbreak, the need for telemedicine is growing rapidly worldwide [
Electronic stethoscopes are promising options to solve the problem of the lack of remote auscultation systems [
To the best of our knowledge, only a few studies have been conducted to determine the utility of real-time remote auscultation using an electronic stethoscope [
An open-label randomized controlled trial was designed to assess the utility of real-time remote auscultation using a Bluetooth-connected electronic stethoscope. Direct auscultation using a traditional stethoscope was used as control. To standardize and enhance the reliability of the assessment, we used a lung simulator for lung auscultation and a cardiology patient simulator for cardiac auscultation [
This study consisted of a lung auscultation part and a cardiac auscultation part. Each part contained a tutorial and a test session. Prior to the test session, all participants attended a tutorial session to become familiar with the device. Thereafter, participants were randomly assigned (simple randomization) to either the real-time remote auscultation group (intervention group) or the classical auscultation group (control group). The randomization was conducted separately in the lung and cardiac parts. Researchers were blinded in terms of allocation, by using a computer-generated allocation table to assign participants.
In the tutorial sessions, all participants took part in auscultation using a traditional stethoscope (Littmann Cardiology III, 3M, St Paul, MN) on the lung simulator (Lung Sound Auscultation Trainer “LSAT” ver.2, model #MW28, Kyoto Kagaku Co, Ltd, Kyoto, Japan) and on the cardiac patient simulator (Cardiology Patient Simulator “K” ver.2, model #MW10, Kyoto Kagaku Co, Ltd). In each tutorial session, the participant listened to 15 sounds, with the correct classification being provided to participants. A short instruction for the simulator and the correct placements for auscultation were provided. In the tutorial session for lung auscultation, the following 15 sounds were played in a random order: normal lung sounds (standard, loud), wheezes (350-450 Hz, 600-700 Hz, 200-1000 Hz), 2 different rhonchi, stridor (twice), 2 different coarse crackles, 2 different fine crackles, and 2 different pleural friction rubs. In the tutorial session for cardiac auscultation, the following 15 sounds were played in random order: 3 different normal cardiac sounds (no S2 split, S2 split, and S1 split), 3 different third cardiac sounds (S3 gallop enhanced, S3 gallop, and S3-S4 gallop), aortic stenosis (twice), aortic regurgitation (twice), mitral regurgitation (3 times), mitral stenosis, and atrial fibrillation. Each participant was instructed to auscultate in the standardized positions on the simulators: 4 on the anterior and 4 on the posterior on the lung simulator; 4 on the cardiology patient simulator (
The 8 different areas of auscultation on the lung simulator and the 4 different areas of auscultation on the cardiac patient simulator.
In the test sessions, participants in the intervention group auscultated all sounds remotely using an electronic stethoscope (JPES-01, MEMS CORE Co, Ltd, Miyagi, Japan), a Bluetooth transmitter and receiver (BT-DUO, TROND, Eastvale, CA), and a wireless, noise-canceling, stereo headset (WH-1000XM3, Sony Co, Tokyo, Japan), as depicted in
The remote auscultation processes: (A) The researcher is on the left, placing the electronic stethoscope on the cardiac patient simulator, and the participant is on the right listening to the cardiac sounds via a wireless, noise-canceling, stereo headset and Bluetooth transmitter; (B) the remote auscultation equipment including an electronic stethoscope; wireless, noise-canceling, stereo headset; and Bluetooth transmitter (Bluetooth connection is indicated with a dashed double arrow).
For lung auscultation, the same lung simulator (MW28) was used in the tutorial and test sessions. This simulator was designed for medical education training and includes 34 samples of lung sounds recorded from actual patients and reproduced using a high-quality sound system. These lung sounds were classified, according to the American Thoracic Society classification system, as continuous (wheezes, rhonchi, or stridor) or discontinuous (fine or coarse crackles) [
For cardiac auscultation, the same cardiology patient simulator (MW10) was used in the tutorial and test sessions. This simulator was designed for medical education training and includes 88 cases of cardiac sounds recorded from actual patients and reproduced using a high-quality sound system.
The electronic stethoscope is equipped with pressure-sensitive sensors, and the signals are converted into sound waves. It is also equipped with a volume regulator and a frequency filter. The filter has a bell mode, diaphragm mode, and wide mode, which enhance the 20-100 Hz, 200-2000 Hz, and 20-2000 Hz frequency bands, respectively. In the lung and cardiac parts, we used the diaphragm mode and the bell mode, respectively. The transmitter transferred the sounds from the lung simulator to the headset via Bluetooth (A2DP: Advanced Audio Distribution Profile).
Age, sex, and years since obtaining a degree in medicine were collected from all participants as baseline demographic data. All participants’ answers for each sound in the test session were collected. The primary outcome measure was the test score in each group. The rates of correct answers for each sound were the secondary outcome measures.
The correct answer in each group was compared using the Fisher exact test for primary and secondary outcome measures. Continuous variables for participant baseline characteristics are presented as medians (IQRs) and were compared using the Mann-Whitney
In total, 20 physicians in the Department of Diagnostic and Generalist Medicine of Dokkyo Medical University were enrolled in the final analysis (
Flowchart of participant inclusion in the study.
Baseline characteristics of participants in the classical and remote cardiopulmonary auscultation groups.
|
Lung auscultation | Cardiac auscultation | ||||
Variable | Remote lung auscultation (n=11) | Classical lung auscultation (n=9) | Remote cardiac auscultation (n=6) | Classical cardiac auscultation (n=14) | ||
Age (years), median (IQR) | 34.0 (7.0) | 29.0 (9.0) | .25a | 32.5 (6.3) | 32.5 (6.5) | .99a |
Men, n (%) | 9 (82) | 7 (78) | .82b | 6 (100) | 11 (79) | .99b |
Years after graduation (years), median (IQR) | 10.0 (6.0) | 4.0 (5.0) | .15a | 8.0 (4.8) | 7.4 (5.5) | .78a |
aMann-Whitney
bFisher exact test.
Test scores and rates of correct answers for each lung sound are summarized in
Details of the answers for lung auscultation are supplied in
Lung sounds correctly identified.
Variable | Remote auscultation (n=11) | Classical auscultation (n=9) | |
Total, n/N (%) | 80/110 (72.7) | 71/90 (78.9) | .32 |
Normal, n/N (%) | 16/22 (72.7) | 18/18 (100) | .99 |
Wheezes, n/N (%) | 25/33 (75.8) | 19/27 (70.4) | .64 |
Rhonchi, n/N (%) | 9/11 (81.8) | 5/9 (55.6) | .21 |
Coarse crackles, n/N (%) | 7/11 (63.6) | 7/9 (77.8) | .50 |
Fine crackles, n/N (%) | 9/11 (81.8) | 6/9 (66.7) | .44 |
Pleural friction rubs, n/N (%) | 3/11 (27.3) | 7/9 (77.8) | .03 |
Stridor, n/N (%) | 11/11 (100) | 9/9 (100) | N/Ab |
aFisher exact test.
bN/A: not applicable.
Details of the participants’ answers for lung auscultation in the intervention (remote lung auscultation) group.
Correct answer | Normal | Wheezes | Rhonchi | Coarse crackles | Fine crackles | Pleural friction rubs | Stridor |
Normal (n=22) | 16 | 0 | 0 | 2 | 0 | 4 | 0 |
Wheezes (n=33) | 2 | 25 | 3 | 0 | 0 | 1 | 2 |
Rhonchi (n=11) | 0 | 1 | 9 | 0 | 0 | 0 | 1 |
Coarse crackles (n=11) | 2 | 0 | 0 | 7 | 0 | 2 | 0 |
Fine crackles (n=11) | 0 | 0 | 0 | 2 | 9 | 0 | 0 |
Pleural friction rubs (n=11) | 5 | 1 | 0 | 2 | 0 | 3 | 0 |
Stridor (n=11) | 0 | 0 | 0 | 0 | 0 | 0 | 11 |
Details of the participants’ answers for lung auscultation in the control (traditional lung auscultation) group.
Correct answer | Normal | Wheezes | Rhonchi | Coarse crackles | Fine crackles | Pleural friction rubs | Stridor |
Normal (n=18) | 18 | 0 | 0 | 0 | 0 | 0 | 0 |
Wheezes (n=27) | 0 | 19 | 6 | 0 | 0 | 0 | 2 |
Rhonchi (n=9) | 0 | 2 | 5 | 0 | 0 | 0 | 2 |
Coarse crackles (n=9) | 0 | 0 | 0 | 7 | 2 | 0 | 0 |
Fine crackles (n=9) | 0 | 0 | 0 | 2 | 6 | 1 | 0 |
Pleural friction rubs (n=9) | 1 | 0 | 1 | 0 | 0 | 7 | 0 |
Stridor (n=9) | 0 | 0 | 0 | 0 | 0 | 0 | 9 |
Test scores and rates of correct answers for each cardiac sound are summarized in
Details of the answers in the remote cardiac auscultation group are provided in
Cardiac sounds correctly identified.
Variable | Remote auscultation (n=6) | Classical auscultation (n=14) | |
Total, n/N (%) | 50/60 (83.8) | 119/140 (85.0) | .77 |
Normal, n/N (%) | 9/12 (75.0) | 26/28 (92.9) | .14 |
S3, n/N (%) | 8/12 (66.7) | 22/28 (78.6) | .43 |
Aortic stenosis, n/N (%) | 5/6 (83.3) | 14/14 (100) | .99 |
Aortic regurgitation, n/N (%) | 6/6 (100) | 13/14 (92.9) | .99 |
Mitral stenosis, n/N (%) | 5/6 (83.8) | 7/14 (50.0) | .19 |
Mitral regurgitation, n/N (%) | 11/12 (91.7) | 23/28 (82.1) | .45 |
Atrial fibrillation, n/N (%) | 6/6 (100) | 14/14 (100) | N/Ab |
aFisher exact test.
bN/A: not applicable.
Details of the participants’ answers for cardiac auscultation in the intervention (remote cardiac auscultation) group.
Correct answer | Normal | S3 | Aortic stenosis | Aortic regurgitation | Mitral stenosis | Mitral regurgitation | Atrial fibrillation |
Normal (n=12) | 9 | 2 | 0 | 0 | 1 | 0 | 0 |
S3 (n=12) | 4 | 8 | 0 | 0 | 0 | 0 | 0 |
Aortic stenosis (n=6) | 0 | 0 | 5 | 0 | 0 | 1 | 0 |
Aortic regurgitation (n=6) | 0 | 0 | 0 | 6 | 0 | 0 | 0 |
Mitral stenosis (n=6) | 0 | 0 | 0 | 0 | 5 | 1 | 0 |
Mitral regurgitation (n=12) | 0 | 0 | 0 | 0 | 1 | 11 | 0 |
Atrial fibrillation (n=6) | 0 | 0 | 0 | 0 | 0 | 0 | 6 |
Details of the participants’ answers for cardiac auscultation in the control (traditional cardiac auscultation) group.
Correct answer | Normal | S3 | Aortic stenosis | Aortic regurgitation | Mitral stenosis | Mitral regurgitation | Atrial fibrillation |
Normal (n=28) | 26 | 2 | 0 | 0 | 0 | 0 | 0 |
S3 (n=28) | 5 | 22 | 0 | 0 | 1/28 | 0 | 0 |
Aortic stenosis (n=14) | 0 | 0 | 14 | 0 | 0 | 0 | 0 |
Aortic regurgitation (n=14) | 0 | 0 | 0 | 13 | 1 | 0 | 0 |
Mitral stenosis (n=14) | 0 | 0 | 0 | 1 | 7 | 6 | 0 |
Mitral regurgitation (n=28) | 0 | 0 | 1 | 0 | 4 | 23 | 0 |
Atrial fibrillation (n=14) | 0 | 0 | 0 | 0 | 0 | 0 | 14 |
In this study, there were 4 main findings. First, using a simulator, we demonstrated that the utility of real-time remote auscultation using a Bluetooth-connected electronic stethoscope was comparable to that of direct auscultation using a classic stethoscope. From previous finding of lung auscultation, coarse crackles, fine crackles, wheezes, and stridor are useful for diagnosing bronchitis or pneumonia [
Second, the rate of correct answers for pleural friction rubs was lower in the real-time remote lung auscultation group than in the direct lung auscultation group. Therefore, it would be challenging to diagnose pleuritis with real-time remote lung auscultation [
Third, in the real-time remote lung auscultation group, we observed a trend for confusion of normal lung sounds and pleural friction rubs. Respecting pleural friction rubs, 45% were misclassified as normal lung sounds in the remote auscultation group in this study. According to the participants, placement of the electronic stethoscope to the surface of the lung simulator caused a bit of noise. Electronic stethoscopes are sensitive to electronic and ambient noise, and this placement noise may be the cause of the difficulty observed in auscultation of pleural friction rub.
Fourth, the rate of correct answers for mitral stenosis was higher in the real-time remote cardiac auscultation than in the direct cardiac auscultation group. According to the participants, the monitoring screen of the simulator was on the caudal side. The screen showed a heartbeat icon regardless of whether it was the systolic or diastolic phase without any waveform. In the direct cardiac auscultation group, it was difficult to watch a display with auscultation. On the other hand, in the real-time remote auscultation group, the participants could watch the screen to detect the systolic or diastolic phase with auscultation. This may have been the cause for the misinterpretations between mitral stenosis sounds and mitral regurgitation sounds in the direct auscultation group.
There were 3 strengths of note in this study. First, use of simulators allowed us to gather standardized data, reducing bias. Second, the direct comparison of a novel auscultation technology with classical auscultation as control adds value to this randomized controlled study. Third, all participants were physicians who specialized in general internal medicine. Thus, the study participants were representative of general physicians working in community hospitals or clinics, the main population expected to perform auscultation in routine clinical practice.
This study was a pilot study and had several limitations. First, the sample size was small and did not include real patient data. Fully powered trials need to be conducted to better show equivalence. There was grouping variation through simple randomization, especially in the cardiac part, with 6 in the intervention group vs 14 in the control group. This grouping variation may have affected the detection power in this study. Therefore, in future studies, the efficacy of real-time remote auscultation has to be confirmed at the bedside with a larger sample size. Second, as the researcher who placed the electronic stethoscope on the simulators could not hear the sounds while doing so, the timing of the change in auscultation position could not be adjusted for optimum auscultation. Participants in the classical auscultation group were able to change the auscultation position on their own, which may have given this group an advantage over the remote auscultation group. Third, the respiratory rate and phase of crackle could not be adjusted with the lung simulator. The default respiratory rate was slower than that of real patients with respiratory diseases. Therefore, the results from this study may not be generalizable to auscultation at the bedside. Fourth, in this study, the technique used for classical auscultation was not standardized. This may have limited the reproducibility of our results. Fifth, there might be some dependences among answers within-subject.
To the best of our knowledge, there has been no other study in which real-time remote auscultation and classical auscultation were directly compared. In terms of the accuracy of classical auscultation using the simulator, our results, which showed variable accuracy depending on the type of sounds, were consistent with previous studies [
In a previous study of the accuracy of identifying lung sounds using classical auscultation, stridor was not included in the evaluation [
We are aware of 1 study reporting results regarding the utility of real-time remote auscultation [
This study demonstrates that the utility of a Bluetooth-connected, real-time remote auscultation system is comparable to that of classical, direct auscultation, except for pleural friction rubs. Future studies focused on real-time auscultation through Wi-Fi or the internet are warranted. Furthermore, this study leads the way for further studies in real patients with fully powered trials. In a future study, visualized waves of sounds [
The format of the questionnaire for identification of the 10 lung sounds.
The format of the questionnaire for identification of the 10 cardiac sounds.
CONSORT-eHEALTH checklist (V 1.6.1).
This study was made possible using the resources from the Department of Diagnostic and Generalist Medicine, Dokkyo Medical University. Special thanks to Mr Masahiro Sato, manager of the MEMS CORE, Miyagi, Japan, who advised to adjust the electronic stethoscope. Special thanks to Mr Yukio Hanatani, chief executive officer of SMART GATE, Tokyo, Japan, who advised to adjust the electronic devices. An electronic stethoscope (JPES-01) used in this study was provided by MEMS CORE, Miyagi, Japan.
TH, YH, KI, SK, YA, and TS contributed to the study concept and design. TH and YH performed the statistical analyses. TH contributed to the drafting of the manuscript. YH, KI, and TS contributed to the critical revision of the manuscript for relevant intellectual content. All authors read and approved the final manuscript.
None declared.