http://informahealthcare.com/jmt ISSN: 0309-1902 (print), 1464-522X (electronic) J Med Eng Technol, 2014; 38(6): 307–310 ! 2014 Informa UK Ltd. DOI: 10.3109/03091902.2014.921253
INNOVATION
Prototype electronic stethoscope vs conventional stethoscope for auscultation of heart sounds
J Med Eng Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/20/15 For personal use only.
Daniel A. Kelmenson*1, Janae K. Heath1, Stephanie A. Ball2, Haytham M. A. Kaafarani3, Elisabeth M. Baker2, Daniel D. Yeh3, Edward A. Bittner4, Matthias Eikermann4, and Jarone Lee3 1
Department of Medicine, 2Department of Nursing, 3Division of Trauma, Emergency Surgery and Surgical Critical Care, and 4Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, 55 Fruit St, Bigelow 7th Floor, Boston, MA, USA Abstract
Keywords
In an effort to decrease the spread of hospital-acquired infections, many hospitals currently use disposable plastic stethoscopes in patient rooms. As an alternative, this study examines a prototype electronic stethoscope that does not break the isolation barrier between clinician and patient and may also improve the diagnostic accuracy of the stethoscope exam. This study aimed to investigate whether the new prototype electronic stethoscope improved auscultation of heart sounds compared to the standard conventional isolation stethoscope. In a controlled, non-blinded, cross-over study, clinicians were randomized to identify heart sounds with both the prototype electronic stethoscope and a conventional stethoscope. The primary outcome was the score on a 10-question heart sound identification test. In total, 41 clinicians completed the study. Subjects performed significantly better in the identification of heart sounds when using the prototype electronic stethoscope (median ¼ 9 [7–10] vs 8 [6–9] points, p value 50.0001). Subjects also significantly preferred the prototype electronic stethoscope. Clinicians using a new prototype electronic stethoscope achieved greater accuracy in identification of heart sounds and also universally favoured the new device, compared to the conventional stethoscope.
Hospital-acquired infection, ICU, infection control, physical exam, stethoscope
1. Introduction Multiple studies have evaluated the persistence of multi-drugresistant organisms (MDRO) on tools used in patient care and many hospital devices, such as stethoscopes, have been identified as vectors for transmission of hospital-acquired infections (HAI) [1–6]. It has been estimated that 80–100% of healthcare providers’ stethoscopes are contaminated with two or more pathogens (on the stethoscope diaphragm and/or the ear pieces) [4]. Disinfection is the current method of reducing HAI, although poor compliance often limits the effectiveness of this practise [1,2,7,8]. To further minimize the risk of spread of MDRO, hospitals have utilized plastic disposable stethoscopes (one-stethoscope-per-patient standard) to limit patient-to-patient transmission. Unfortunately, the sound quality through the plastic disposable stethoscopes is poor, decreasing the sensitivity and overall utility of the stethoscope as part of the physical exam. Ultimately, the conventional disposable stethoscopes frequently go unused, likely due to a combination of poor sound quality and inconvenience. There have been multiple attempts to create electronic stethoscopes to address some of these problems; however, *Corresponding author. Email: [email protected]
History Received 29 March 2014 Accepted 29 April 2014
replicating acoustics through electronic methods has been challenging. Specifically, problems result from amplification of ambient noise and subsequent interference with auscultated sounds. Poor sound fidelity through speakers had previously hampered the development of one-stethoscope-per-patient electronic stethoscopes with acceptable sound quality. Through advances in acoustic technology, a prototype of an electronic stethoscope (Elegant StethoscopeÕ , Elegant Medical LLC, New Hyde Park, NY) was developed, which was predominantly designed to maintain the isolation barrier, while increasing the value of the stethoscope exam and integrating easily into clinician workflow. The prototype electronic stethoscope was created with the ability to amplify sounds for assessment while minimizing interference of ambient noise, achieving a sound fidelity equal or greater to traditional stethoscopes (despite sounds being played through a speaker). It also has the ability to store sound files for further analysis or comparison to previously stored sounds, with clear implications for both patient care and medical education. Furthermore, it upholds the one-stethoscope-per-patient (rather than one-stethoscope-per-clinician) standard while preserving the integrity of the bedside physical exam [9]. The prototype electronic stethoscope consists of a diaphragm that transmits sounds via tubing to a speaker that
J Med Eng Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/20/15 For personal use only.
308
D. A. Kelmenson et al.
stays in the patient’s room. There is no risk of breaking the isolation barrier between patient and clinician since sounds are played through a speaker and, thus, the clinician does not have to place the stethoscope in their ears. The ultimate goal is to improve the quality (and the diagnostic accuracy) of the stethoscope exam when using this new technology, as compared to the traditional non-electronic stethoscope, while also preventing transmission of MDRO. Prior to assessing the prototype electronic stethoscope’s impact on direct patient care, we sought to compare it to the plastic disposable (standard) stethoscope to assess for improvement in auscultation. We hypothesized that the prototype electronic stethoscope will provide improved auscultation of heart sounds. We assessed the user’s ability to interpret heart sounds using the prototype electronic stethoscope as compared to the standard disposable plastic stethoscope. We also assessed user preference comparing the prototype electronic and conventional stethoscopes in five domains. This new prototype electronic stethoscope could offer a unique tool for patient care, an advance in medical education and another way to decrease the patient-to-patient spread of HAI.
J Med Eng Technol, 2014; 38(6): 307–310
Figure 1. Prototype electronic stethoscope set-up. A ¼ Speaker pad; B ¼ Auscultation diaphragm; C ¼ Base station; D ¼ iPhone; E ¼ Subject; F ¼ Examiner.
2. Methods 2.1. Subject characteristics Eligible subjects included all nurses, nurse practitioners, physicians, physician assistants, medical students or nursing students working at Massachusetts General Hospital. We contacted potential subjects by email and flyers in 2013. All subjects provided informed consent and the local institutional review board approved the study (IRB protocol #2013P000971). 2.2. Study design This was a randomized, controlled, non-blinded, cross-over study. Neither the subject nor the examiner could be blinded due to the nature of the intervention. Prior to auscultation, each subject watched a 3-min video that introduced the prototype electronic stethoscope, explained how to use it, and outlined the purpose of the study. Subjects were randomized to initial testing with the prototype electronic or conventional stethoscope via coin flip. Subjects completed a 10-question test (Test A) with the chosen stethoscope, followed by completion of the subsequent test (Test B) using the alternative stethoscope. For auscultation, a speaker pad was used for both Test A and Test B. When a stethoscope diaphragm (either electronic or conventional) is placed on the speaker pad, sounds are transmitted to the stethoscope and then to the listener. For the test involving the prototype electronic stethoscope, the set-up included the speaker pad and an auscultation diaphragm connected via electrical tubing to a base station (that records sounds from the auscultation diaphragm and plays the sounds through a speaker) (Figures 1 and 2). For the test involving the conventional stethoscope (provided by the examiner), the set-up included the speaker pad and a conventional stethoscope (MediChoice Lightweight Single-Head Stethoscope, Owens & Minor, Mechanicsville, VA), the standard stethoscope used in isolation beds in our institution. When using the
Figure 2. Auscultation diaphragm. The user can turn the diaphragm on or off, record sounds to the base station and increase or decrease the volume.
electronic stethoscope base station, the subjects had the option to speed up, slow down or increase the volume of the heart sounds as heard through the speaker. For each sound, the subject could listen as long as they liked. For the conventional stethoscope, the subject could listen as long as they liked but, given the nature of the conventional stethoscope, there was no ability to change the volume or speed of the sounds. For Test A, the subject listened to 10 unidentified sounds from the Blaufuss Sound Builder iPhone application (Blaufuss Medical Multimedia Laboratories, LLC, Rolling Hills Estates, CA) [10]. For each sound, the subject had to select the correct answer from six provided choices (normal heart sound, third heart sound, fourth heart sound, early systolic murmur, continuous murmur and early diastolic murmur). Some of the sounds were repeated more than once in the 10-question test. For the subsequent Test B, the subject listened to the same 10 sounds from the Blaufuss Sound Builder iPhone application (albeit in a different order than the first test) and selected the correct answer from the same six answer choices. This method of testing cardiac auscultation using an electronic stethoscope has been previously validated as a scoring tool [11].
Prototype electronic stethoscope
DOI: 10.3109/03091902.2014.921253
Following the completion of both 10-question tests, the subject completed a survey that collected their demographic information (age, job title and years of experience). The subject also answered Likert-type items that compared the prototype electronic stethoscope to the conventional stethoscope in five categories (diagnostic accuracy, ease of use, potential as a teaching tool, potential to reduce infection and potential to impact patient care). This completed the study and the examiner then graded Test A and Test B (with one point awarded per question).
J Med Eng Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/20/15 For personal use only.
2.3. Study measures Since neither the subject nor the examiner was blinded, we obtained objective measures of performance for our primary outcome to minimize the possibility of bias. The primary outcome was the total number of correct answers on the 10-question test, comparing performance with the prototype electronic stethoscope to that with the conventional stethoscope. The secondary outcomes were the individual scores on each of the five Likert-type items comparing the two stethoscopes. 2.4. Statistical analysis The primary analysis was designed to determine if the prototype electronic stethoscope was superior to the conventional stethoscope with regards to the total score on the 10-question heart sound identification test. We estimated that a sample size of 36 participants (each of which crossed over to the other stethoscope) would provide 80% power to detect a one-point difference between the two stethoscope groups, assuming a standard deviation of 2 with a two-sided significance level of 0.05. We first looked for any order effect (of which stethoscope went first) using a Wilcoxon rank sum test. If testing showed no significant difference, the participants from the two different orders were combined for analysis. Medians and interquartile ranges were used to summarize the distribution of the total test scores. The difference in total score between stethoscopes was compared using a Wilcoxon signed-rank test. We used means and standard deviations to describe subject demographics and the Likert-type items and we used one-sample t-tests to assess significance of the Likert-type items. A two-sided p50.05 was considered statistically significant. SAS software, version 9.3 (The SAS Instititue, Cary, NC) was used for all analyses.
3. Results 3.1. Study population A total of 41 subjects were enrolled in the study in October– November 2013, including 21 physicians, 17 nurses, two nurse practitioners and one medical student. The subjects were an average of 32 (SD ¼ 9) years old with 6 (SD ¼ 9) years of work experience. Following randomization, 21 subjects were assigned to use the conventional stethoscope first and then the prototype electronic stethoscope and 20 subjects performed the tests in the opposite order (electronic followed by conventional). The order in which subjects performed the testing did not make a significant difference on
309
Table 1. Secondary outcomes. Outcome* Diagnostic accuracy Ease of use Potential as a teaching tool Potential to reduce infection Potential to impact patient care
Mean (SD) 4 3.6 4.9 4.4 4.2
(0.9) (1.3) (0.4) (0.8) (0.8)
p valuey 50.0001 0.005 50.0001 50.0001 50.0001
*For each of the secondary outcome questions, the subjects were asked to ‘Please rate the prototype stethoscope compared with the conventional, non-electronic stethoscope across the following variables’ from 1–5 on a Likert-type scale, with 1 representing ‘prototype is not as good as conventional stethoscope’, 3 representing ‘prototype is equally good as conventional stethoscope’ and 5 representing ‘prototype is better than the conventional stethoscope’ yp values were calculated using a one-sample t-test, examining whether the mean was significantly different from 3 (equally good).
the heart sound 10-question test scores (p ¼ 0.18) and, thus, we combined the results of both groups for our data analysis. 3.2. Outcomes Scores on the 10-question test (the primary outcome) were significantly higher when subjects used the prototype electronic stethoscope (median ¼ 9 points, interquartile range ¼ 7–10) as compared to the conventional stethoscope (median ¼ 8 points, interquartile range ¼ 6–9, p value 50.0001). Subjects also significantly preferred the prototype in all examined domains (diagnostic accuracy, ease of use, potential as a teaching tool, potential to reduce infection and potential to impact patient care) (Table 1).
4. Discussion In this study, there was a significant improvement in correct auscultation of heart sounds when comparing the prototype electronic stethoscope to the conventional disposable stethoscope, as measured by scores on a 10-question test (the primary outcome). There was also a significant user preference for the prototype in all examined domains, specifically perceived diagnostic accuracy, ease of use, potential as a teaching tool, potential to reduce infection and potential to impact patient care. Our findings demonstrate both a proven and perceived benefit to the prototype stethoscope, addressing auscultation quality and user dislike as two of the major problems limiting the use of conventional disposable stethoscopes. This new technology has the potential to improve medical education and patient care, while easily incorporating into daily clinical workflow. The prototype stethoscope constitutes an innovative tool for teaching in medical education, allowing all healthcare providers the ability to simultaneously hear, interpret and discuss the stethoscope exam. More directly, this new device may lead to improved accuracy in a key aspect of the physical exam and, thus, potential improvement in patient care. Current hospital solutions to address stethoscopes as a vector in transmission of HAI involve the use of plastic disposable stethoscopes, with limited compliance given the poor sound quality, inconvenience and failure to uphold the isolation barrier (since the stethoscope touches both the patient and the clinician’s ears). Our study introduces an alternative to the current standard, suggesting an
J Med Eng Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/20/15 For personal use only.
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improvement in auscultation with the prototype electronic stethoscope compared to the traditional disposable stethoscope. Through technological advances, this prototype is the first electronic stethoscope that maintains sound fidelity while transmitting through speakers, equalling or surpassing traditional stethoscopes in the accuracy of sound auscultation. There are a number of strengths and potential limitations in our study. The cross-over study design reduced the potential for confounding based on differences in subject experience or level of training, as each subject participated in each group. Nevertheless, the cross-over design does have the potential for learner effects and bias; however, randomization of order of the testing diminished this effect. Our auscultation exam was also simulated under tightly controlled conditions, without direct patient auscultation, so generalization to realworld patient-care settings remains uncertain. The findings of improvement in auscultation using the prototype electronic stethoscope likely stem from the ability to amplify heart sounds while minimizing ambient noise interference. This creates a new avenue for effective auscultation, patient care and diagnosis and, in conjunction with the patient specific nature of the prototype, has potential applications in isolation rooms of hospitals. Further applications to medical education can be implied from the ability to record and store data, allowing for further analysis of auscultated sounds (such as listening for changes over time in the characteristics of a heart murmur in a patient with suspected endocarditis) and integration with electronic medical records. It is still unclear if the prototype can translate to patient care in intensive care unit settings; however, our study is the first step in evaluating this prototype for a broad range of uses. Future steps include evaluation in real-life situations (rather than simulated sounds), as well as broadening the application of the prototype electronic stethoscope to evaluation of noncardiac sounds (such as lung auscultation). Given the potential for an impact in infection control, the prototype’s role in transmission of HAI should also be evaluated, as compared to conventional non-electronic stethoscopes. In conclusion, the prototype electronic stethoscope led to improvement in auscultation on simulated heart sounds, as well as perceived improvement in auscultation by clinicians. This has a multitude of implications, including potential improvement in patient care, potential to decrease infection transmission and a new avenue for medical education. Our study demonstrated improvement in auscultation when
J Med Eng Technol, 2014; 38(6): 307–310
using the prototype electronic stethoscope and further evaluation of its utility in real-life situations (specifically intensive care units) is warranted.
Acknowledgements We would like to thank Yuchiao Chang for her assistance with statistical analysis.
Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
References 1. Boyce, J.M., 2007, Environmental contamination makes an important contribution to hospital infection. Journal of Hospital Infection, 65(Suppl 2), 50–54. 2. Whittington, A.M., Whitlow, G., Hewson, D., Thomas, C., and Brett, S.J., 2009, Bacterial contamination of stethoscopes on the intensive care unit. Anaesthesia, 64, 620–624. 3. Cohen, S.R., McCormack, D.J., Youkhana, A., and Wall, R., 2003, Bacterial colonization of stethoscopes and the effect of cleaning. Journal of Hospital Infection, 55, 236–237. 4. Smith, M.A., Mathewson, J.J., Ulert, I.A., Scerpella, E.G., and Ericsson, C.D., 1996, Contaminated stethoscopes revisited. Archives of Internal Medicine, 156, 82–84. 5. Jones, J.S., Hoerle, D., and Riekse, R., 1995, Stethoscopes: a potential vector of infection? Annals of Emergency Medicine, 26, 296–299. 6. Marinella, M.A., Pierson, C., and Chenoweth, C., 1997, The stethoscope. A potential source of nosocomial infection? Archives of Internal Medicine, 157, 786–790. 7. Doebbeling, B.N., Stanley, G.L., Sheetz, C.T., Pfaller, M.A., Houston, A.K., Annis, L., Li, N., Wenzel, R.P., 1992, Comparative efficacy of alternative hand-washing agents in reducing nosocomial infections in intensive care units. New England Journal of Medicine, 327, 88–93. 8. Breathnach, A.S., Jenkins, D.R., and Pedler, S.J., 1992, Stethoscopes as possible vectors of infection by staphylococci. British Medical Journal, 305, 1573–1574. 9. Habboushe, J., 2009, Electronic stethoscope apparatus. US Patent 2009/0279708. 10. Vukanovic-Criley, J.M., Criley, S., Warde, C.M., Boker, J.R., Guevara-Matheus, L., Churchill, W.H., Nelson, W.P., Criley, J.M., 2006, Competency in cardiac examination skills in medical students, trainees, physicians, and faculty: a multicenter study. Archives of Internal Medicine, 166, 610–616. 11. Lam, M.Z.C., Lee, T.J., Boey, P.Y., Ng, W.F., Hey, H.W., Ho, K.Y., Cheong, P.Y., 2005, Factors influencing cardiac auscultation proficiency in physician trainees. Singapore Medical Journal, 46, 11–14.
INNOVATION
Prototype electronic stethoscope vs conventional stethoscope for auscultation of heart sounds
J Med Eng Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/20/15 For personal use only.
Daniel A. Kelmenson*1, Janae K. Heath1, Stephanie A. Ball2, Haytham M. A. Kaafarani3, Elisabeth M. Baker2, Daniel D. Yeh3, Edward A. Bittner4, Matthias Eikermann4, and Jarone Lee3 1
Department of Medicine, 2Department of Nursing, 3Division of Trauma, Emergency Surgery and Surgical Critical Care, and 4Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, 55 Fruit St, Bigelow 7th Floor, Boston, MA, USA Abstract
Keywords
In an effort to decrease the spread of hospital-acquired infections, many hospitals currently use disposable plastic stethoscopes in patient rooms. As an alternative, this study examines a prototype electronic stethoscope that does not break the isolation barrier between clinician and patient and may also improve the diagnostic accuracy of the stethoscope exam. This study aimed to investigate whether the new prototype electronic stethoscope improved auscultation of heart sounds compared to the standard conventional isolation stethoscope. In a controlled, non-blinded, cross-over study, clinicians were randomized to identify heart sounds with both the prototype electronic stethoscope and a conventional stethoscope. The primary outcome was the score on a 10-question heart sound identification test. In total, 41 clinicians completed the study. Subjects performed significantly better in the identification of heart sounds when using the prototype electronic stethoscope (median ¼ 9 [7–10] vs 8 [6–9] points, p value 50.0001). Subjects also significantly preferred the prototype electronic stethoscope. Clinicians using a new prototype electronic stethoscope achieved greater accuracy in identification of heart sounds and also universally favoured the new device, compared to the conventional stethoscope.
Hospital-acquired infection, ICU, infection control, physical exam, stethoscope
1. Introduction Multiple studies have evaluated the persistence of multi-drugresistant organisms (MDRO) on tools used in patient care and many hospital devices, such as stethoscopes, have been identified as vectors for transmission of hospital-acquired infections (HAI) [1–6]. It has been estimated that 80–100% of healthcare providers’ stethoscopes are contaminated with two or more pathogens (on the stethoscope diaphragm and/or the ear pieces) [4]. Disinfection is the current method of reducing HAI, although poor compliance often limits the effectiveness of this practise [1,2,7,8]. To further minimize the risk of spread of MDRO, hospitals have utilized plastic disposable stethoscopes (one-stethoscope-per-patient standard) to limit patient-to-patient transmission. Unfortunately, the sound quality through the plastic disposable stethoscopes is poor, decreasing the sensitivity and overall utility of the stethoscope as part of the physical exam. Ultimately, the conventional disposable stethoscopes frequently go unused, likely due to a combination of poor sound quality and inconvenience. There have been multiple attempts to create electronic stethoscopes to address some of these problems; however, *Corresponding author. Email: [email protected]
History Received 29 March 2014 Accepted 29 April 2014
replicating acoustics through electronic methods has been challenging. Specifically, problems result from amplification of ambient noise and subsequent interference with auscultated sounds. Poor sound fidelity through speakers had previously hampered the development of one-stethoscope-per-patient electronic stethoscopes with acceptable sound quality. Through advances in acoustic technology, a prototype of an electronic stethoscope (Elegant StethoscopeÕ , Elegant Medical LLC, New Hyde Park, NY) was developed, which was predominantly designed to maintain the isolation barrier, while increasing the value of the stethoscope exam and integrating easily into clinician workflow. The prototype electronic stethoscope was created with the ability to amplify sounds for assessment while minimizing interference of ambient noise, achieving a sound fidelity equal or greater to traditional stethoscopes (despite sounds being played through a speaker). It also has the ability to store sound files for further analysis or comparison to previously stored sounds, with clear implications for both patient care and medical education. Furthermore, it upholds the one-stethoscope-per-patient (rather than one-stethoscope-per-clinician) standard while preserving the integrity of the bedside physical exam [9]. The prototype electronic stethoscope consists of a diaphragm that transmits sounds via tubing to a speaker that
J Med Eng Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/20/15 For personal use only.
308
D. A. Kelmenson et al.
stays in the patient’s room. There is no risk of breaking the isolation barrier between patient and clinician since sounds are played through a speaker and, thus, the clinician does not have to place the stethoscope in their ears. The ultimate goal is to improve the quality (and the diagnostic accuracy) of the stethoscope exam when using this new technology, as compared to the traditional non-electronic stethoscope, while also preventing transmission of MDRO. Prior to assessing the prototype electronic stethoscope’s impact on direct patient care, we sought to compare it to the plastic disposable (standard) stethoscope to assess for improvement in auscultation. We hypothesized that the prototype electronic stethoscope will provide improved auscultation of heart sounds. We assessed the user’s ability to interpret heart sounds using the prototype electronic stethoscope as compared to the standard disposable plastic stethoscope. We also assessed user preference comparing the prototype electronic and conventional stethoscopes in five domains. This new prototype electronic stethoscope could offer a unique tool for patient care, an advance in medical education and another way to decrease the patient-to-patient spread of HAI.
J Med Eng Technol, 2014; 38(6): 307–310
Figure 1. Prototype electronic stethoscope set-up. A ¼ Speaker pad; B ¼ Auscultation diaphragm; C ¼ Base station; D ¼ iPhone; E ¼ Subject; F ¼ Examiner.
2. Methods 2.1. Subject characteristics Eligible subjects included all nurses, nurse practitioners, physicians, physician assistants, medical students or nursing students working at Massachusetts General Hospital. We contacted potential subjects by email and flyers in 2013. All subjects provided informed consent and the local institutional review board approved the study (IRB protocol #2013P000971). 2.2. Study design This was a randomized, controlled, non-blinded, cross-over study. Neither the subject nor the examiner could be blinded due to the nature of the intervention. Prior to auscultation, each subject watched a 3-min video that introduced the prototype electronic stethoscope, explained how to use it, and outlined the purpose of the study. Subjects were randomized to initial testing with the prototype electronic or conventional stethoscope via coin flip. Subjects completed a 10-question test (Test A) with the chosen stethoscope, followed by completion of the subsequent test (Test B) using the alternative stethoscope. For auscultation, a speaker pad was used for both Test A and Test B. When a stethoscope diaphragm (either electronic or conventional) is placed on the speaker pad, sounds are transmitted to the stethoscope and then to the listener. For the test involving the prototype electronic stethoscope, the set-up included the speaker pad and an auscultation diaphragm connected via electrical tubing to a base station (that records sounds from the auscultation diaphragm and plays the sounds through a speaker) (Figures 1 and 2). For the test involving the conventional stethoscope (provided by the examiner), the set-up included the speaker pad and a conventional stethoscope (MediChoice Lightweight Single-Head Stethoscope, Owens & Minor, Mechanicsville, VA), the standard stethoscope used in isolation beds in our institution. When using the
Figure 2. Auscultation diaphragm. The user can turn the diaphragm on or off, record sounds to the base station and increase or decrease the volume.
electronic stethoscope base station, the subjects had the option to speed up, slow down or increase the volume of the heart sounds as heard through the speaker. For each sound, the subject could listen as long as they liked. For the conventional stethoscope, the subject could listen as long as they liked but, given the nature of the conventional stethoscope, there was no ability to change the volume or speed of the sounds. For Test A, the subject listened to 10 unidentified sounds from the Blaufuss Sound Builder iPhone application (Blaufuss Medical Multimedia Laboratories, LLC, Rolling Hills Estates, CA) [10]. For each sound, the subject had to select the correct answer from six provided choices (normal heart sound, third heart sound, fourth heart sound, early systolic murmur, continuous murmur and early diastolic murmur). Some of the sounds were repeated more than once in the 10-question test. For the subsequent Test B, the subject listened to the same 10 sounds from the Blaufuss Sound Builder iPhone application (albeit in a different order than the first test) and selected the correct answer from the same six answer choices. This method of testing cardiac auscultation using an electronic stethoscope has been previously validated as a scoring tool [11].
Prototype electronic stethoscope
DOI: 10.3109/03091902.2014.921253
Following the completion of both 10-question tests, the subject completed a survey that collected their demographic information (age, job title and years of experience). The subject also answered Likert-type items that compared the prototype electronic stethoscope to the conventional stethoscope in five categories (diagnostic accuracy, ease of use, potential as a teaching tool, potential to reduce infection and potential to impact patient care). This completed the study and the examiner then graded Test A and Test B (with one point awarded per question).
J Med Eng Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/20/15 For personal use only.
2.3. Study measures Since neither the subject nor the examiner was blinded, we obtained objective measures of performance for our primary outcome to minimize the possibility of bias. The primary outcome was the total number of correct answers on the 10-question test, comparing performance with the prototype electronic stethoscope to that with the conventional stethoscope. The secondary outcomes were the individual scores on each of the five Likert-type items comparing the two stethoscopes. 2.4. Statistical analysis The primary analysis was designed to determine if the prototype electronic stethoscope was superior to the conventional stethoscope with regards to the total score on the 10-question heart sound identification test. We estimated that a sample size of 36 participants (each of which crossed over to the other stethoscope) would provide 80% power to detect a one-point difference between the two stethoscope groups, assuming a standard deviation of 2 with a two-sided significance level of 0.05. We first looked for any order effect (of which stethoscope went first) using a Wilcoxon rank sum test. If testing showed no significant difference, the participants from the two different orders were combined for analysis. Medians and interquartile ranges were used to summarize the distribution of the total test scores. The difference in total score between stethoscopes was compared using a Wilcoxon signed-rank test. We used means and standard deviations to describe subject demographics and the Likert-type items and we used one-sample t-tests to assess significance of the Likert-type items. A two-sided p50.05 was considered statistically significant. SAS software, version 9.3 (The SAS Instititue, Cary, NC) was used for all analyses.
3. Results 3.1. Study population A total of 41 subjects were enrolled in the study in October– November 2013, including 21 physicians, 17 nurses, two nurse practitioners and one medical student. The subjects were an average of 32 (SD ¼ 9) years old with 6 (SD ¼ 9) years of work experience. Following randomization, 21 subjects were assigned to use the conventional stethoscope first and then the prototype electronic stethoscope and 20 subjects performed the tests in the opposite order (electronic followed by conventional). The order in which subjects performed the testing did not make a significant difference on
309
Table 1. Secondary outcomes. Outcome* Diagnostic accuracy Ease of use Potential as a teaching tool Potential to reduce infection Potential to impact patient care
Mean (SD) 4 3.6 4.9 4.4 4.2
(0.9) (1.3) (0.4) (0.8) (0.8)
p valuey 50.0001 0.005 50.0001 50.0001 50.0001
*For each of the secondary outcome questions, the subjects were asked to ‘Please rate the prototype stethoscope compared with the conventional, non-electronic stethoscope across the following variables’ from 1–5 on a Likert-type scale, with 1 representing ‘prototype is not as good as conventional stethoscope’, 3 representing ‘prototype is equally good as conventional stethoscope’ and 5 representing ‘prototype is better than the conventional stethoscope’ yp values were calculated using a one-sample t-test, examining whether the mean was significantly different from 3 (equally good).
the heart sound 10-question test scores (p ¼ 0.18) and, thus, we combined the results of both groups for our data analysis. 3.2. Outcomes Scores on the 10-question test (the primary outcome) were significantly higher when subjects used the prototype electronic stethoscope (median ¼ 9 points, interquartile range ¼ 7–10) as compared to the conventional stethoscope (median ¼ 8 points, interquartile range ¼ 6–9, p value 50.0001). Subjects also significantly preferred the prototype in all examined domains (diagnostic accuracy, ease of use, potential as a teaching tool, potential to reduce infection and potential to impact patient care) (Table 1).
4. Discussion In this study, there was a significant improvement in correct auscultation of heart sounds when comparing the prototype electronic stethoscope to the conventional disposable stethoscope, as measured by scores on a 10-question test (the primary outcome). There was also a significant user preference for the prototype in all examined domains, specifically perceived diagnostic accuracy, ease of use, potential as a teaching tool, potential to reduce infection and potential to impact patient care. Our findings demonstrate both a proven and perceived benefit to the prototype stethoscope, addressing auscultation quality and user dislike as two of the major problems limiting the use of conventional disposable stethoscopes. This new technology has the potential to improve medical education and patient care, while easily incorporating into daily clinical workflow. The prototype stethoscope constitutes an innovative tool for teaching in medical education, allowing all healthcare providers the ability to simultaneously hear, interpret and discuss the stethoscope exam. More directly, this new device may lead to improved accuracy in a key aspect of the physical exam and, thus, potential improvement in patient care. Current hospital solutions to address stethoscopes as a vector in transmission of HAI involve the use of plastic disposable stethoscopes, with limited compliance given the poor sound quality, inconvenience and failure to uphold the isolation barrier (since the stethoscope touches both the patient and the clinician’s ears). Our study introduces an alternative to the current standard, suggesting an
J Med Eng Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/20/15 For personal use only.
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improvement in auscultation with the prototype electronic stethoscope compared to the traditional disposable stethoscope. Through technological advances, this prototype is the first electronic stethoscope that maintains sound fidelity while transmitting through speakers, equalling or surpassing traditional stethoscopes in the accuracy of sound auscultation. There are a number of strengths and potential limitations in our study. The cross-over study design reduced the potential for confounding based on differences in subject experience or level of training, as each subject participated in each group. Nevertheless, the cross-over design does have the potential for learner effects and bias; however, randomization of order of the testing diminished this effect. Our auscultation exam was also simulated under tightly controlled conditions, without direct patient auscultation, so generalization to realworld patient-care settings remains uncertain. The findings of improvement in auscultation using the prototype electronic stethoscope likely stem from the ability to amplify heart sounds while minimizing ambient noise interference. This creates a new avenue for effective auscultation, patient care and diagnosis and, in conjunction with the patient specific nature of the prototype, has potential applications in isolation rooms of hospitals. Further applications to medical education can be implied from the ability to record and store data, allowing for further analysis of auscultated sounds (such as listening for changes over time in the characteristics of a heart murmur in a patient with suspected endocarditis) and integration with electronic medical records. It is still unclear if the prototype can translate to patient care in intensive care unit settings; however, our study is the first step in evaluating this prototype for a broad range of uses. Future steps include evaluation in real-life situations (rather than simulated sounds), as well as broadening the application of the prototype electronic stethoscope to evaluation of noncardiac sounds (such as lung auscultation). Given the potential for an impact in infection control, the prototype’s role in transmission of HAI should also be evaluated, as compared to conventional non-electronic stethoscopes. In conclusion, the prototype electronic stethoscope led to improvement in auscultation on simulated heart sounds, as well as perceived improvement in auscultation by clinicians. This has a multitude of implications, including potential improvement in patient care, potential to decrease infection transmission and a new avenue for medical education. Our study demonstrated improvement in auscultation when
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using the prototype electronic stethoscope and further evaluation of its utility in real-life situations (specifically intensive care units) is warranted.
Acknowledgements We would like to thank Yuchiao Chang for her assistance with statistical analysis.
Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
References 1. Boyce, J.M., 2007, Environmental contamination makes an important contribution to hospital infection. Journal of Hospital Infection, 65(Suppl 2), 50–54. 2. Whittington, A.M., Whitlow, G., Hewson, D., Thomas, C., and Brett, S.J., 2009, Bacterial contamination of stethoscopes on the intensive care unit. Anaesthesia, 64, 620–624. 3. Cohen, S.R., McCormack, D.J., Youkhana, A., and Wall, R., 2003, Bacterial colonization of stethoscopes and the effect of cleaning. Journal of Hospital Infection, 55, 236–237. 4. Smith, M.A., Mathewson, J.J., Ulert, I.A., Scerpella, E.G., and Ericsson, C.D., 1996, Contaminated stethoscopes revisited. Archives of Internal Medicine, 156, 82–84. 5. Jones, J.S., Hoerle, D., and Riekse, R., 1995, Stethoscopes: a potential vector of infection? Annals of Emergency Medicine, 26, 296–299. 6. Marinella, M.A., Pierson, C., and Chenoweth, C., 1997, The stethoscope. A potential source of nosocomial infection? Archives of Internal Medicine, 157, 786–790. 7. Doebbeling, B.N., Stanley, G.L., Sheetz, C.T., Pfaller, M.A., Houston, A.K., Annis, L., Li, N., Wenzel, R.P., 1992, Comparative efficacy of alternative hand-washing agents in reducing nosocomial infections in intensive care units. New England Journal of Medicine, 327, 88–93. 8. Breathnach, A.S., Jenkins, D.R., and Pedler, S.J., 1992, Stethoscopes as possible vectors of infection by staphylococci. British Medical Journal, 305, 1573–1574. 9. Habboushe, J., 2009, Electronic stethoscope apparatus. US Patent 2009/0279708. 10. Vukanovic-Criley, J.M., Criley, S., Warde, C.M., Boker, J.R., Guevara-Matheus, L., Churchill, W.H., Nelson, W.P., Criley, J.M., 2006, Competency in cardiac examination skills in medical students, trainees, physicians, and faculty: a multicenter study. Archives of Internal Medicine, 166, 610–616. 11. Lam, M.Z.C., Lee, T.J., Boey, P.Y., Ng, W.F., Hey, H.W., Ho, K.Y., Cheong, P.Y., 2005, Factors influencing cardiac auscultation proficiency in physician trainees. Singapore Medical Journal, 46, 11–14.
