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Article

Blue as an Underrated Alternative to Green: Photoplethysmographic Heartbeat Intervals Estimation under Two Temperature Conditions

1
Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu, Kitakyushu, Fukuoka 808-0135, Japan
2
Omsk State Technical University, 11 Prospekt Mira, 644050 Omsk, Russia
*
Author to whom correspondence should be addressed.
Shchelkanova, E.; Shchelkanov, A.; Shchapova, L.; Shibata T. An Exploration of Blue PPG Signal Using a Novel Color Sensorbased PPG System. In Proceedings of the 2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), Montreal, QC, Canada, 20–24 July 2020; pp. 4414–4420.
Academic Editor: Pawel Strumillo
Sensors 2021, 21(12), 4241; https://doi.org/10.3390/s21124241
Received: 19 April 2021 / Revised: 21 May 2021 / Accepted: 8 June 2021 / Published: 21 June 2021
(This article belongs to the Collection Medical Applications of Sensor Systems and Devices)
Since photoplethysmography (PPG) sensors are usually placed on open skin areas, temperature interference can be an issue. Currently, green light is the most widely used in the reflectance PPG for its relatively low artifact susceptibility. However, it has been known that hemoglobin absorption peaks at the blue part of the spectrum. Despite this fact, blue light has received little attention in the PPG field. Blue wavelengths are commonly used in phototherapy. Combining blue light-based treatments with simultaneous blue PPG acquisition could be potentially used in patients monitoring and studying the biological effects of light. Previous studies examining the PPG in blue light compared to other wavelengths employed photodetectors with inherently lower sensitivity to blue, thereby biasing the results. The present study assessed the accuracy of heartbeat intervals (HBIs) estimation from blue and green PPG signals, acquired under baseline and cold temperature conditions. Our PPG system is based on TCS3472 Color Sensor with equal sensitivity to both parts of the light spectrum to ensure unbiased comparison. The accuracy of the HBIs estimates, calculated with five characteristic points (PPG systolic peak, maximum of the first PPG derivative, maximum of the second PPG derivative, minimum of the second PPG derivative, and intersecting tangents) on both PPG signal types, was evaluated based on the electrocardiographic values. The statistical analyses demonstrated that in all cases, the HBIs estimation accuracy of blue PPG was nearly equivalent to the G PPG irrespective of the characteristic point and measurement condition. Therefore, blue PPG can be used for cardiovascular parameter acquisition. This paper is an extension of work originally presented at the 42nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society. View Full-Text
Keywords: photoplethysmography; blue light; color sensor; heartbeat intervals photoplethysmography; blue light; color sensor; heartbeat intervals
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MDPI and ACS Style

Shchelkanova, E.; Shchapova, L.; Shchelkanov, A.; Shibata, T. Blue as an Underrated Alternative to Green: Photoplethysmographic Heartbeat Intervals Estimation under Two Temperature Conditions. Sensors 2021, 21, 4241. https://doi.org/10.3390/s21124241

AMA Style

Shchelkanova E, Shchapova L, Shchelkanov A, Shibata T. Blue as an Underrated Alternative to Green: Photoplethysmographic Heartbeat Intervals Estimation under Two Temperature Conditions. Sensors. 2021; 21(12):4241. https://doi.org/10.3390/s21124241

Chicago/Turabian Style

Shchelkanova, Evgeniia, Liia Shchapova, Alexander Shchelkanov, and Tomohiro Shibata. 2021. "Blue as an Underrated Alternative to Green: Photoplethysmographic Heartbeat Intervals Estimation under Two Temperature Conditions" Sensors 21, no. 12: 4241. https://doi.org/10.3390/s21124241

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