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Instantaneous Respiratory Estimation from Thoracic Impedance by Empirical Mode Decomposition

Department of Electrical Engineering, Hwa Hsia University of Technology, 111, Gongzhuan Rd., Zhonghe, New Taipei City 23568, Taiwan
Department of Electrical Engineering, Chang Gung University, 259 Wenhwa 1st Road, Kweishan, Taoyuan 33302, Taiwan
Department of Cardiology, Chang Gung Memorial Hospital, 5 Fu-Hsing Street, Kweishan, Taoyuan 33305, Taiwan
Author to whom correspondence should be addressed.
Academic Editor: Vittorio M.N. Passaro
Sensors 2015, 15(7), 16372-16387;
Received: 8 June 2015 / Revised: 1 July 2015 / Accepted: 3 July 2015 / Published: 7 July 2015
(This article belongs to the Section Physical Sensors)
PDF [925 KB, uploaded 7 July 2015]


Impedance plethysmography provides a way to measure respiratory activity by sensing the change of thoracic impedance caused by inspiration and expiration. This measurement imposes little pressure on the body and uses the human body as the sensor, thereby reducing the need for adjustments as body position changes and making it suitable for long-term or ambulatory monitoring. The empirical mode decomposition (EMD) can decompose a signal into several intrinsic mode functions (IMFs) that disclose nonstationary components as well as stationary components and, similarly, capture respiratory episodes from thoracic impedance. However, upper-body movements usually produce motion artifacts that are not easily removed by digital filtering. Moreover, large motion artifacts disable the EMD to decompose respiratory components. In this paper, motion artifacts are detected and replaced by the data mirrored from the prior and the posterior before EMD processing. A novel intrinsic respiratory reconstruction index that considers both global and local properties of IMFs is proposed to define respiration-related IMFs for respiration reconstruction and instantaneous respiratory estimation. Based on the experiments performing a series of static and dynamic physical activates, our results showed the proposed method had higher cross correlations between respiratory frequencies estimated from thoracic impedance and those from oronasal airflow based on small window size compared to the Fourier transform-based method. View Full-Text
Keywords: impedance plethysmography; respiratory disorder; empirical mode decomposition; intrinsic mode function impedance plethysmography; respiratory disorder; empirical mode decomposition; intrinsic mode function

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Wang, F.-T.; Chan, H.-L.; Wang, C.-L.; Jian, H.-M.; Lin, S.-H. Instantaneous Respiratory Estimation from Thoracic Impedance by Empirical Mode Decomposition. Sensors 2015, 15, 16372-16387.

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