Unobtrusive Photoplethysmographic Monitoring Under the Foot Sole While in a Standing Posture

Overview

Journal Sensors (Basel)

Publisher MDPI

Specialty Biotechnology

Date 2018 Sep 29

PMID 30261647

Citations 3

Authors

Seunghyeok Hong

Kwang Suk Park

Affiliations

Soon will be listed here.

Abstract

Photoplethysmography (PPG) of the foot sole could provide additional health-related information compared with traditional PPG of the finger or wrist. Previously, foot PPG required the procedural binding of a light-emitting diode (LED)-photodetector (PD) pair. We achieved PPG of the foot sole without binding any sensors to the foot while the participant stood in a natural standing position on the testing device. Foot PPG was performed using multiple LED-PD pairs to overcome motion artefacts caused by stabilization. We identified regions of the sole suitable for reliable sensor positioning with optimal LED-PD pairs on the basis of the estimated heart rate (HR) and signal quality index derived by dynamic time warping (wSQI). The first experiment included four participants with direct skin-to-sensor contact, and the results showed a mean HR estimation error of 0.01 beats/min and a wSQI of 0.909. The extended experiment with 53 participants, which involved including a gap between the skin and sensors to consider real-life applications, yielded a mean HR estimation error of 0.638 beats/min and a wSQI of 0.751. Based on the selection ratio of optimal LED-PD pairs, the best region of the sole for PPG was the midfoot, except the medial longitudinal arch. In conclusion, we confirmed that foot PPG using multiple LED-PD pairs is appropriate for HR evaluation and further applications.

Citing Articles

Feasibility of Electrodermal Activity and Photoplethysmography Data Acquisition at the Foot Using a Sock Form Factor.

Ferreira A, da Silva H, Alves H, Marques N, Fred A Sensors (Basel). 2023; 23(2).

PMID: 36679418 PMC: 9865091. DOI: 10.3390/s23020620.

Insole-Based Systems for Health Monitoring: Current Solutions and Research Challenges.

Subramaniam S, Majumder S, Faisal A, Deen M Sensors (Basel). 2022; 22(2).

PMID: 35062398 PMC: 8780030. DOI: 10.3390/s22020438.

Illumination Adaptation in a Multi-Wavelength Opto-Electronic Patch Sensor.

Yan L, Yu Y, Hu S, Mulvaney D, Blanos P, Alharbi S Sensors (Basel). 2020; 20(17).

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References

Ginosar Y, Weiniger C, Meroz Y, Kurz V, Bdolah-Abram T, Babchenko A . Pulse oximeter perfusion index as an early indicator of sympathectomy after epidural anesthesia. Acta Anaesthesiol Scand. 2009; 53(8):1018-26. DOI: 10.1111/j.1399-6576.2009.01968.x. View

Nitzan M, Khanokh B, Slovik Y . The difference in pulse transit time to the toe and finger measured by photoplethysmography. Physiol Meas. 2002; 23(1):85-93. DOI: 10.1088/0967-3334/23/1/308. View

Baek H, Chung G, Kim K, Park K . A smart health monitoring chair for nonintrusive measurement of biological signals. IEEE Trans Inf Technol Biomed. 2011; 16(1):150-8. DOI: 10.1109/TITB.2011.2175742. View

Zheng Y, Ding X, Poon C, Lo B, Zhang H, Zhou X . Unobtrusive sensing and wearable devices for health informatics. IEEE Trans Biomed Eng. 2014; 61(5):1538-54. PMC: 7176476. DOI: 10.1109/TBME.2014.2309951. View

Baek H, Chung G, Kim K, Kim J, Park K . Photoplethysmogram measurement without direct skin-to-sensor contact using an adaptive light source intensity control. IEEE Trans Inf Technol Biomed. 2009; 13(6):1085-8. DOI: 10.1109/TITB.2009.2031108. View

Babchenko A, Davidson E, Adler D, Ginosar Y, Kurz V, Nitzan M . Increase in pulse transit time to the foot after epidural anaesthesia treatment. Med Biol Eng Comput. 2001; 38(6):674-9. DOI: 10.1007/BF02344874. View

Loram I, Lakie M . Direct measurement of human ankle stiffness during quiet standing: the intrinsic mechanical stiffness is insufficient for stability. J Physiol. 2002; 545(3):1041-53. PMC: 2290720. DOI: 10.1113/jphysiol.2002.025049. View

Gonzalez-Landaeta R, Casas O, Pallas-Areny R . Heart rate detection from an electronic weighing scale. Annu Int Conf IEEE Eng Med Biol Soc. 2007; 2007:6283-6. DOI: 10.1109/IEMBS.2007.4353791. View

Allen J, Murray A . Age-related changes in peripheral pulse timing characteristics at the ears, fingers and toes. J Hum Hypertens. 2002; 16(10):711-7. DOI: 10.1038/sj.jhh.1001478. View

10.

Allen J, Oates C, Lees T, Murray A . Photoplethysmography detection of lower limb peripheral arterial occlusive disease: a comparison of pulse timing, amplitude and shape characteristics. Physiol Meas. 2005; 26(5):811-21. DOI: 10.1088/0967-3334/26/5/018. View

11.

Li Q, Clifford G . Dynamic time warping and machine learning for signal quality assessment of pulsatile signals. Physiol Meas. 2012; 33(9):1491-501. DOI: 10.1088/0967-3334/33/9/1491. View

12.

Cobb J, Claremont D . Noninvasive measurement techniques for monitoring of microvascular function in the diabetic foot. Int J Low Extrem Wounds. 2005; 1(3):161-9. DOI: 10.1177/153473460200100303. View

13.

Bland J, Altman D . Measuring agreement in method comparison studies. Stat Methods Med Res. 1999; 8(2):135-60. DOI: 10.1177/096228029900800204. View

14.

Martin S, Carek A, Kim C, Ashouri H, Inan O, Hahn J . Weighing Scale-Based Pulse Transit Time is a Superior Marker of Blood Pressure than Conventional Pulse Arrival Time. Sci Rep. 2016; 6:39273. PMC: 5157040. DOI: 10.1038/srep39273. View

15.

Diaz D, Casas O, Pallas-Areny R . Heart rate detection from single-foot plantar bioimpedance measurements in a weighing scale. Annu Int Conf IEEE Eng Med Biol Soc. 2010; 2010:6489-92. DOI: 10.1109/IEMBS.2010.5627358. View

16.

Kato Y, Nambu M, Imura M, Kuroda Y, Oshiro O . Smart sensing of cardiovascular physiological information from soles without direct skin contact. Annu Int Conf IEEE Eng Med Biol Soc. 2013; 2012:5806-9. DOI: 10.1109/EMBC.2012.6347314. View

17.

Shin J, Lee K, Park K . Non-constrained monitoring of systolic blood pressure on a weighing scale. Physiol Meas. 2009; 30(7):679-93. DOI: 10.1088/0967-3334/30/7/011. View

18.

Park S, Baek H, Park K, Kim Y . Photoplethysmographic signals to predict the success of lumbar sympathetic blockade for lower extremity pain. J Int Med Res. 2014; 42(4):938-48. DOI: 10.1177/0300060514532619. View

19.

Koski A, Juhola M . Segmentation of digital signals based on estimated compression ratio. IEEE Trans Biomed Eng. 1996; 43(9):928-38. DOI: 10.1109/10.532127. View

20.

Stahl S, An H, Dinkel D, Noble J, Lee J . How accurate are the wrist-based heart rate monitors during walking and running activities? Are they accurate enough?. BMJ Open Sport Exerc Med. 2016; 2(1):e000106. PMC: 5117066. DOI: 10.1136/bmjsem-2015-000106. View