Non-Contact Measurements of Electrocardiogram and Cough-Associated Electromyogram from the Neck Using In-Pillow Common Cloth Electrodes: A Proof-of-Concept Study

Figures

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  Figure 1. In-pillow capacitive cloth electrodes. (a) Top-view configuration of the electrodes. (b) Cross-sectional configuration of (a) along the dotted line (1)–(2). The electrodes have a five-layered structure. The top layers consist of a negative electrode (−elec.) and a positive electrode (+elec.).

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  Figure 2. Proposed measuring system. (a) Electrode layout and block diagram. (b) Function of front-end voltage follower (FVF) in capacitive biopotential measurements (c) Circuit diagram of the FVF employed in the measuring system. A bootstrapping technique and varistor element were adopted to increase the voltage-dependent input impedance.

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  Figure 3. Protocol of experiment in this study.

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  Figure 4. Flowchart of selecting the coughing segment in the EMGref and cEMG data for the following discrete-time Fourier transform (DFT) analysis.

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  Figure 5. Simultaneous measurements of subject B with the proposed or commercial system obtained during a two-cough experiment. (a) Recordings of ECGref, cECG, differentiated cECG, EMGref, and cEMG. (b) Enlarged ECGref and cECG waveforms and (c) enlarged EMGref and cEMG signals corresponding to the dotted rectangular sections in (a).

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  Figure 6. Simultaneous recordings of ECGref, cECG and filtered and differentiated cECG of subject E obtained with the commercial system (first stage) or the proposed system (second and third stages) during the 2-min segment before the first two-cough experiment. Inverted triangles marks in the third stage show the detected bottoms of the R-waves.

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  Figure 7. Comparison of frequency–amplitude spectra between coughing and resting segments for (a) EMGref and (b) cEMG data shown in Figure 5c. The red line corresponds to the spectra for coughing segments, while the blue line corresponds to that for resting segments. (Subject #B).

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  Figure 8. Comparison of mean total spectral amplitudes (TSAs) between resting and coughing in the EMGref and cEMG signals of (a) each subject, and (b) the group of all subjects.

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  Figure 9. Recordings of EMGref and cEMG including a two-cough cycle for subjects E and C. In the cEMG signals, firings considered to be associated with inhalation (a) and swallowing (b) were also confirmed by the two-cough procedure.