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| 2. |
- Hult, Peter, 1964-, et al.
(författare)
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A method for respiration in monitoring by use of a bioacoustic signal
- 2000
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Ingår i: Medical signal and information processing MEDSIP,2000. - : IET. - 0852967284 ; , s. 22-25
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Konferensbidrag (refereegranskat)abstract
- The sound that generates during the act of respiration can be picked up by a bioacoustic sensor, a specially designed microphone. The aim of the work was to describe a method for monitoring of respiration and where the start and stop of the respiration phases can be timed accurately. A method is presented where the time position of the different respiration phases can be determined by a time resolution of 51 ms. A microphone applied over the trachea and the features of the respiration sounds frequency content was used for the development of the method
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| 3. |
- Hult, Peter, 1964-, et al.
(författare)
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An improved bioacoustic method for monitoring of respiration
- 2004
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Ingår i: Technology and Health Care. - 0928-7329 .- 1878-7401. ; 12:4, s. 323-332
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Hult, Peter, 1964-, et al.
(författare)
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Detection of the third heart sound using a tailored wavelet approach : Method verification
- 2005
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 43:2, s. 212-217
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Tidskriftsartikel (refereegranskat)abstract
- Heart sounds can be considered as mechanical fingerprints of myocardial function. The third heart sound normally occurs in children but disappears with maturation. The sound can also appear in patients with heart failure. The sound is characterised by its low-amplitude and low-frequency content, which makes it difficult to identify by the traditional use of the stethoscope. A wavelet-based method has recently been developed for detection of the third heart sound. This study investigated if the third heart sound could be identified in patients with heart failure using this detection method. The method was also compared with auscultation using conventional phonocardiography and with characterisation of the patients with echocardiography. In the first study, 87% of the third heart sounds were detected using the wavelet method, 12% were missed, and 6% were false positive. In study 2, the wavelet-detection method identified 87% of the patients using the third heart sound, and regular phonocardiography identified two (25%) of the subjects. © IFMBE: 2005.
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| 5. |
- Hult, Peter, 1964-, et al.
(författare)
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Detection of the third heart sound using a tailored wavelet approach
- 2004
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 42:2, s. 253-258
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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