1. The Electronic Esophageal Stethoscope
Joseph H. McIsaac, III, MD, MS, Hartford Hospital Anesthesiology
Megan Bowers, University of Connecticut School of Engineering
Stuart Chen, University of Illinois at Urbana-Champaign
Esophageal Stethoscope:
An Overview
Used to monitor
anesthetized
patients.
Greater amplitude
of heart and lung
sounds than with
precordial
stethoscope.
Room for Change
Use of esophageal stethoscope
criticized for its subjectivity.
No standard method exists for
recording heart and lung diagnoses
during surgery.
Continuous auscultation difficult in
modern OR setting.
Project Goals
Device for safe
OR recording.
Software program
to record patient
sounds and
remove ambient
room noise.
Visual
representation
of heart and
lung sounds.
Automated
diagnostic
ability.
Discussion of Results
LabVIEWTM
successfully records high-
quality stereo .wav files in OR.
Signal subtraction in LabVIEWTM
is not
satisfactory for removing ambient room
noise.
Wavelet analysis holds the most
promise for a noise cancellation
algorithm for this application.
Short-Term Goals
Amplify patient sounds.
Employ noise cancellation algorithm
such as wavelet analysis to improve
quality of patient sounds.
Develop a method of visual
representation of heart and lung
sounds.
Future Plans
Refine hardware and software designs.
Program the recording software to
automatically diagnose the incoming heart
and lung sounds.
Produce a marketable device to eliminate
the subjectivity currently associated with
the esophageal stethoscope.
References
1. Manecke GR et al. Auscultation revisited: The waveform and spectral
characteristics of breath sounds during general anesthesia. J Clin Monit,
14:231-240, 1997.
2. Kim D, Tavel ME. Assessment of severity of aortic stenosis through time-
frequency analysis of murmur. Chest. 124(5):1638-44, 2003.
3. Liatsos C, et al. Bowel sounds analysis: a novel noninvasive method for
diagnosis of small-volume ascites. Dig Dis Sci. 48(8):1630-6, 2003.
4. St. Clair C, McIsaac J. The Electronic Esophageal Stethoscope: New Analysis
of Heart and Lung Sounds, 2002.
5. Geaney L, McIsaac J. The Electronic Esophageal Stethoscope: The Frequency
Response of the Esophageal Stethoscope, 2003.
6. Charbonneu G et al. Basic Techniques for respiratory sound analysis.
European Respiratory Review. 10:77, 625-635, 2000.
Stuart Chen
Dave Kaputa
Dr. Newton DeFaria
Acknowledgements
Step 3: System
Characterization
Test frequency
response of adult
esophageal
stethoscope at all
frequencies.
Apply results to
noise cancellation
approaches.
Gain of Esophageal Stethoscope
Gain
(dB)
Frequency (Hz)
Step 2: Test Recordings
 In OR: 30-second recordings of normal and
abnormal heart and lung sounds.
 Adjust LabVIEWTM
program settings to
reduce ambient room noise.
 Analysis and verification of recordings using
MATLABTM
programming environment.
Recording Setup
Laptop
computer
External sound
card
Two miniature
condenser
microphones in
plastic housing
Dual channel
preamp with
29dB gain
Step 1: Programming
 LabVIEWTM
graphical programming environment.
 Records esophageal stethoscope sounds as
stereo .wav files.
 Processes recordings to remove noise.