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Removing respiratory artefacts from transthoracic bioimpedance spectroscopy measurements
KTH, Skolan för teknik och hälsa (STH). Philips Research Europe, High Tech. Campus 34, 5656AE, Eindhoven, Netherlands; ACTLab., Signal Processing Systems, TU Eindhoven, 5600MB Eindhoven, Netherlands.
Philips Research Europe, High Tech. Campus 34, 5656AE, Eindhoven, Netherlands.ORCID-id: 0000-0001-7807-8682
KTH, Skolan för teknik och hälsa (STH).
KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system. University of Borås, Sweden.
Visa övriga samt affilieringar
2013 (Engelska)Ingår i: XV International Conference on Electrical Bio-Impedance (ICEBI) & XIV Conference on Electrical Impedance Tomography (EIT), Institute of Physics Publishing (IOPP), 2013, Vol. 434, nr 1Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

Transthoracic impedance spectroscopy (TIS) measurements from wearable textile electrodes provide a tool to remotely and non-invasively monitor patient health. However, breathing and cardiac processes inevitably affect TIS measurements, since they are sensitive to changes in geometry and air or fluid volumes in the thorax. This study aimed at investigating the effect of respiration on Cole parameters extracted from TIS measurements and developing a method to suppress artifacts. TIS data were collected from 10 participants at 16 frequencies (range: 10 kHz - 1 MHz) using a textile electrode system (Philips Technologie Gmbh). Simultaneously, breathing volumes and frequency were logged using an electronic spirometer augmented with data from a breathing belt. The effect of respiration on TIS measurements was studied at paced (10 and 16 bpm) deep and shallow breathing. These measurements were repeated for each subject in three different postures (lying down, reclining and sitting). Cole parameter estimation was improved by assessing the tidal expiration point thus removing breathing artifacts. This leads to lower intra-subject variability between sessions and a need for less measurements points to accurately assess the spectra. Future work should explore algorithmic artifacts compensation models using breathing and posture or patient contextual information to improve ambulatory transthoracic impedance measurements.

Ort, förlag, år, upplaga, sidor
Institute of Physics Publishing (IOPP), 2013. Vol. 434, nr 1
Serie
Journal of Physics Conference Series, ISSN 1742-6588 ; 434:1
Nyckelord [en]
Air, Artificial intelligence, Electric impedance, Electric impedance tomography, Parameter estimation, Patient monitoring, Textiles
Nationell ämneskategori
Annan medicinteknik
Identifikatorer
URN: urn:nbn:se:kth:diva-136737DOI: 10.1088/1742-6596/434/1/012018ISI: 000326512200018Scopus ID: 2-s2.0-84877333426OAI: oai:DiVA.org:kth-136737DiVA, id: diva2:676939
Konferens
15th International Conference on Electrical Bio-Impedance, ICEBI 2013 and 14th Conference on Electrical Impedance Tomography, EIT 2013; Heilbad Heiligenstadt; Germany; 22 April 2013 through 25 April 2013
Anmärkning

QC 20131209

Tillgänglig från: 2013-12-08 Skapad: 2013-12-08 Senast uppdaterad: 2016-04-18Bibliografiskt granskad
Ingår i avhandling
1. Aspects of Electrical Bioimpedance Spectrum Estimation
Öppna denna publikation i ny flik eller fönster >>Aspects of Electrical Bioimpedance Spectrum Estimation
2014 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Electrical bioimpedance spectroscopy (EBIS) has been used to assess the status or composition of various types of tissue, and examples of EBIS include body composition analysis (BCA) and tissue characterisation for skin cancer detection. EBIS is a non-invasive method that has the potential to provide a large amount of information for diagnosis or monitoring purposes, such as the monitoring of pulmonary oedema, i.e., fluid accumulation in the lungs. However, in many cases, systems based on EBIS have not become generally accepted in clinical practice. Possible reasons behind the low acceptance of EBIS could involve inaccurate models; artefacts, such as those from movements; measurement errors; and estimation errors. Previous thoracic EBIS measurements aimed at pulmonary oedema have shown some uncertainties in their results, making it difficult to produce trustworthy monitoring methods. The current research hypothesis was that these uncertainties mostly originate from estimation errors. In particular, time-varying behaviours of the thorax, e.g., respiratory and cardiac activity, can cause estimation errors, which make it tricky to detect the slowly varying behaviour of this system, i.e., pulmonary oedema.

The aim of this thesis is to investigate potential sources of estimation error in transthoracic impedance spectroscopy (TIS) for pulmonary oedema detection and to propose methods to prevent or compensate for these errors.   This work is mainly focused on two aspects of impedance spectrum estimation: first, the problems associated with the delay between estimations of spectrum samples in the frequency-sweep technique and second, the influence of undersampling (a result of impedance estimation times) when estimating an EBIS spectrum. The delay between frequency sweeps can produce huge errors when analysing EBIS spectra, but its effect decreases with averaging or low-pass filtering, which is a common and simple method for monitoring the time-invariant behaviour of a system. The results show the importance of the undersampling effect as the main estimation error that can cause uncertainty in TIS measurements.  The best time for dealing with this error is during the design process, when the system can be designed to avoid this error or with the possibility to compensate for the error during analysis. A case study of monitoring pulmonary oedema is used to assess the effect of these two estimation errors. However, the results can be generalised to any case for identifying the slowly varying behaviour of physiological systems that also display higher frequency variations.  Finally, some suggestions for designing an EBIS measurement system and analysis methods to avoid or compensate for these estimation errors are discussed.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2014. s. xi, 36
Serie
TRITA-STH : report, ISSN 1653-3836 ; 2014:4
Nyckelord
Electrical Bioimpedance Spectroscopy, Thoracic Bioimpedance Spectroscopy, Sub-Nyquist Sampling, Undersampling, Aliasing in Electrical Bioimpedance, Bioimpedance Estimation Error.
Nationell ämneskategori
Medicinteknik Signalbehandling
Forskningsämne
Medicinsk teknologi; Elektro- och systemteknik
Identifikatorer
urn:nbn:se:kth:diva-145643 (URN)978-91-7595-196-6 (ISBN)
Presentation
2014-08-21, 221, Alfred Nobels Allé 10, Flemingsberg, 15:37 (Engelska)
Opponent
Handledare
Anmärkning

QC 20140604

Tillgänglig från: 2014-06-04 Skapad: 2014-05-23 Senast uppdaterad: 2014-06-04Bibliografiskt granskad

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Abtahi, FarhadSeoane, Fernando

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