The Impact of Contact Force on Signal Quality Indices in Photoplethysmography Measurements

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1 Citation (Scopus)

Abstract

Photoplethysmography (PPG) is widely used to assess cardiovascular health. Yet, its effectiveness is often hindered by external factors like contact force (CF), which significantly affects the accuracy and reliability of measurements. This study investigates how variations in the CF at the index fingertips influence six signal quality indices (SQIs)—including the perfusion index, skewness, kurtosis, entropy, zero-crossing rate, and relative power—using data from 11 healthy participants. Our analysis of normalized CF values reveals that lower CF ranges (0.2 to 0.4) may be optimal for extracting information about perfusion and blood flow. However, they may not be the best range to capture all the physiological details within the PPG pulse. In contrast, higher CF ranges (0.4 to 0.6) enable capturing more complex signals that could be physiologically representative. The findings underscore the necessity of considering viscoelastic tissue properties and individual biomechanical differences, advocating for both the normalization of CF for improved cross-subject comparison and personalized CF calibration to adapt PPG devices to diverse populations. These strategies ensure measurement reliability and consistency, thereby advancing the accuracy of cardiac and vascular assessments. Our study offers guidelines for adjusting the CF levels to balance signal detail and perfusion quality, customized to meet specific analytical requirements, with direct implications for both clinical and research environments.
Original languageEnglish
Article number5704
Pages (from-to)1-18
Number of pages <span style="color:red"p> <font size="1.5"> ✽ </span> </font>18
JournalApplied Sciences (MDPI)
Volume14
Issue number13
DOIs
Publication statusPublished - 29 Jun 2024

Bibliographical note

Funding Information:
We acknowledge VUB for the SRP (Strategic Research Program) LSDS and the IOF-GEAR TECH4HEALTH project funding and ETRO.RDI BAS funding. We also thank the Belgian Development Cooperation through VLIR-UOS (Flemish Interuniversity Council-University Cooperation for Development) in the context of the Institutional University Cooperation program (IUC 2019 Phase 2 UO) with the Universidad de Oriente (Cuba). This work has been supported through the OZR4103 VUB project funding and partially supported by the FWO-Flanders FWOSB106 Ph.D. grant and by Innoviris-Brussels through the ILSF projects BRGEOZ403 and BRGEOZ422.

Publisher Copyright:
© 2024 by the authors.

Keywords

  • photoplethysmography
  • contact force
  • signal morphology
  • signal quality index
  • optimal contact force
  • signal calibration

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