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Bioacoustic principles used in monitoring and diagnostic applications
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The idea behind this work is linked to the experience gained from the long use of the stethoscope, and to the fact that sound originating from the body is a mechanical fingerprint, reflecting the human body functions.

The aims of this thesis have been to develop bioacoustic systems using modern medical signal processing in three applications. The first was to develop a method for monitor the respiration, the second was to develop a detection method for the third heart sound and, the third was to study a swallowing detection technique and look into the potential of bioacoustic development in this area.

Respiratory monitoring is of vital importance in several clinical situations. A bioacoustic signal analysis approach has been developed for monitoring of respiration. This approach includes strategies to differentiate between inspiration and expiration. In two different patient groups, the method has managed to detect 98% of the respiratory cycles.

The third heart sound has been found to be related to heart failure. A tailored wavelet technique has been developed fur detection of the third heart sound. The method has been used in children and in patients with heart failure. The wavelet metod detected 87% of the third heart sounds and only 2% were classified as false positive.

An investigation of an existing method for swallowing detection, computerized laryngeal analyser (CLA), was performed toghether with a pilot study involving swallowing sounds for the detection. The CLA technique was found to be inadequate for swallowing detection. The bioacoustic approach showed promise for detection of swallows.

We expect in the future that bioacoustics will be an important medical field, for diagnosis, monitoring, rehabilitation and education. The methods show potential for increased use, both in hospital and primary care.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2002. , 72 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 778
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-24564Local ID: 6729ISBN: 91-7373-438-1 (print)OAI: oai:DiVA.org:liu-24564DiVA: diva2:244885
Public defence
2002-11-08, Aulan, Administrationshuset, Universitetssjukhuset, Linköping, 10:15 (Swedish)
Opponent
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2013-01-02
List of papers
1. A bioacoustic method for timing of the different phases of the breathing cycle and monitoring of breathing frequency
Open this publication in new window or tab >>A bioacoustic method for timing of the different phases of the breathing cycle and monitoring of breathing frequency
2000 (English)In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 22, no 6, 425-433 p.Article in journal (Refereed) Published
Abstract [en]

It is well known that the flow of air through the trachea during respiration causes vibrations in the tissue near the trachea, which propagate to the surface of the body and can be picked up by a microphone placed on the throat over the trachea. Since the vibrations are a direct result of the airflow, accurate timing of inspiration and expiration is possible. This paper presents a signal analysis solution for automated monitoring of breathing and calculation of the breathing frequency. The signal analysis approach uses tracheal sound variables in the time and frequency domains, as well as the characteristics of the disturbances that can be used to discriminate tracheal sound from noise. One problem associated with the bioacoustic method is its sensitivity for acoustic disturbances, because the microphone tends to pick up all vibrations, independent of their origin. A signal processing method was developed that makes the bioacoustic method clinically useful in a broad variety of situations, for example in intensive care and during certain heart examinations, where information about both the precise timing and the phases of breathing is crucial.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26691 (URN)10.1016/S1350-4533(00)00050-3 (DOI)11279 (Local ID)11279 (Archive number)11279 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2013-01-02
2. An improved bioacoustic method for monitoring of respiration
Open this publication in new window or tab >>An improved bioacoustic method for monitoring of respiration
Show others...
2004 (English)In: Technology and Health Care, ISSN 0928-7329, Vol. 12, no 4, 323-332 p.Article in journal (Refereed) Published
Abstract [en]

Reliable monitoring of respiration plays an important role in a broad spectrum of applications. Today, there are several methods for monitoring respiration, but none of them has proved to be satisfactory in all respects. We have recently developed a bioacoustic method that can accurately time respiration from tracheal sounds. The aim of this study is to tailor this bioacoustic method for monitoring purposes by introducing dedicated signal processing. The method was developed on a material of ten patients and then tested in another ten patients treated in an intensive care unit. By studying the differences in the variation of the spectral content between the different phases of respiration, the described method can distinguish between inspiration and expiration and can extract respiration frequency, and respiration pause periods. The system detected 98% of the inspirations and 99% of the expirations. This method for respiration monitoring has the advantage of being simple, robust and the sensor does not need to be placed closed to the face. A commercial heart microphone was used and we anticipate that further improvement in performance can be achieved trough optimization of sensor design.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-22249 (URN)1416 (Local ID)1416 (Archive number)1416 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2013-01-02
3. Detection of the third heart sound using a tailored wavelet approach
Open this publication in new window or tab >>Detection of the third heart sound using a tailored wavelet approach
2004 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 42, no 2, 253-258 p.Article in journal (Refereed) Published
Abstract [en]

The third heart sound is normally heard during auscultation of younger individuals but disappears with increasing age. However, this sound can appear in patients with heart failure and is thus of potential diagnostic use in these patients. Auscultation of the heart involves a high degree of subjectivity. Furthermore, the third heart sound has low amplitude and a low-frequency content compared with the first and second heart sounds, which makes it difficult for the human ear to detect this sound. It is our belief that it would be of great help to the physician to receive computer-based support through an intelligent stethoscope, to determine whether a third heart sound is present or not. A precise, accurate and low-cost instrument of this kind would potentially provide objective means for the detection of early heart failure, and could even be used in primary health care. In the first step, phonocardiograms from ten children, all known to have a third heart sound, were analysed, to provide knowledge about the sound features without interference from pathological sounds. Using this knowledge, a tailored wavelet analysis procedure was developed to identify the third heart sound automatically, a technique that was shown to be superior to Fourier transform techniques. In the second step, the method was applied to phonocardiograms from heart patients known to have heart failure. The features of the third heart sound in children and of that in patients were shown to be similar. This resulted in a method for the automatic detection of third heart sounds. The method was able to detect third heart sounds effectively (90%), with a low false detection rate (3.7%), which supports its clinical use. The detection rate was almost equal in both the children and patient groups. The method is therefore capable of detecting, not only distinct and clearly visible/audible third heart sounds found in children, but also third heart sounds in phonocardiograms from patients suffering from heart failure.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-22211 (URN)10.1007/BF02344639 (DOI)1369 (Local ID)1369 (Archive number)1369 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2013-01-02
4. Bioacoustic detection of the third heart sound: a preliminary patient study
Open this publication in new window or tab >>Bioacoustic detection of the third heart sound: a preliminary patient study
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Body sounds are related to mechanical processes in the body. Thus, the heart can be seen as a sound generator and the heart sounds as mechanical fingerprints of myocardial function.

This sound normally occurs in children but disappear with maturation. The sound can also appear in patients with heart failure. The sound is characterized by its low amplitude and low frequency content, which makes it difficult to identify by the use of the traditional stethoscope.

We have recently developed a wavelet based method for detection of the third heart sound. Our intention with this study was to investigate if a third heart sound could be identified in patients with a diagnosis of heart failure attending the heart failure clinic using this detection method. It was also our intention to compare our method with auscultation using a conventional phonocardiography, and characterizing the patients with echocardiography.

Using the wavelet method (study 1), 87% of the third heart sounds that were identified from the recordings (with the visual method as a reference) were detected, 12% were missed and 2% were false positive. In study 2, the wavelet detection method identified all (100%) of patients with identified third heart sound and regular phonocardiography identified 2 (13%) of the subjects.

Keyword
Noninvasive, Third heart sound, Wavelet, Heart failure, Heart sounds, Phonocardiogram, Auscultation, Echocardiography
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-86738 (URN)
Available from: 2013-01-02 Created: 2013-01-02 Last updated: 2013-09-26
5. Validation and characterization of the computerized laryngeal analyzer (CLA) technique
Open this publication in new window or tab >>Validation and characterization of the computerized laryngeal analyzer (CLA) technique
1999 (English)In: Dysphagia (New York. Print), ISSN 0179-051X, E-ISSN 1432-0460, Vol. 14, no 4, 191-195 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to investigate the response characteristics of the Computerized Laryngeal Analyzer (CLA) and the validity of the noninvasive CLA method to detect swallowing-induced laryngeal elevation correctly. Two healthy adults and two experimental models were used in the study. The CLA technique identified all swallowing events but was unable to discriminate between swallowing and other movements of the tongue or the neck. The computer program produced a derivated response to a square wave signal. Stepwise bending increments of the sensor displayed a linear amplitude response. The degree of laryngeal elevation could not be estimated with the CLA technique, and it was not possible to draw any reliable conclusions from the recordings as to whether the larynx was moving upward or downward.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-32932 (URN)10.1007/PL00009605 (DOI)18883 (Local ID)18883 (Archive number)18883 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-01-02

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