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Sensors 2018, 18(11), 3870; https://doi.org/10.3390/s18113870

Missing RRI Interpolation Algorithm based on Locally Weighted Partial Least Squares for Precise Heart Rate Variability Analysis

1
The Department of Systems Science, Kyoto University, Kyoto 615-8085, Japan
2
The Department of Material Process Engineering, Nagoya University, Nagoya 464-8601, Japan
*
Author to whom correspondence should be addressed.
Received: 7 October 2018 / Revised: 7 November 2018 / Accepted: 9 November 2018 / Published: 10 November 2018
(This article belongs to the Special Issue Wearable Sensors and Devices for Healthcare Applications)
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Abstract

The R-R interval (RRI) fluctuation in electrocardiogram (ECG) is called heart rate variability (HRV), which reflects activities of the autonomic nervous system (ANS) and has been used for various health monitoring services. Accurate R wave detection is crucial for success in HRV-based health monitoring services; however, ECG artifacts often cause missing R waves and deteriorate the accuracy of HRV analysis. The present work proposes a new missing RRI interpolation technique based on Just-In-Time (JIT) modeling. In the JIT modeling framework, a local regression model is built by weighing samples stored in the database according to the distance from a query and output is estimated only when an estimate is requested. The proposed method builds a local model and estimates missing RRI only when an RRI detection error is detected. Locally weighted partial least squares (LWPLS) is adopted for local model construction. The proposed method is referred to as LWPLS-based RRI interpolation (LWPLS-RI). The performance of the proposed LWPLS-RI was evaluated through its application to RRI data with artificial missing RRIs. We used the MIT-BIH Normal Sinus Rhythm Database for nominal RRI dataset construction. Missing RRIs were artificially introduced and they were interpolated by the proposed LWPLS-RI. In addition, MEAN that replaces the missing RRI by a mean of the past RRI data was compared as a conventional method. The result showed that the proposed LWPLS-RI improved root mean squared error (RMSE) of RRI by about 70% in comparison with MEAN. In addition, the proposed method realized precise HRV analysis. The proposed method will contribute to the realization of precise HRV-based health monitoring services.
Keywords: R wave detection; heart rate variability analysis; Just-In-Time modeling; locally weighted partial least squares R wave detection; heart rate variability analysis; Just-In-Time modeling; locally weighted partial least squares
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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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Kamata, K.; Kinoshita, K.F.T.; Kano, M. Missing RRI Interpolation Algorithm based on Locally Weighted Partial Least Squares for Precise Heart Rate Variability Analysis. Sensors 2018, 18, 3870.

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