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Exploring Near- and Far-Field Effects in Photoplethysmography Signals Across Different Source-Detector Distances.

Ángel Solé Morillo1, Joan Lambert Cause1,2, Kevin De Pauw3,4

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Summary
This summary is machine-generated.

Photoplethysmography (PPG) signal quality varies with distance and light color. Near-field effects significantly impact the DC component, potentially affecting physiological measurements like SpO2.

Keywords:
PPGfar-fieldinfluencing factorsinstrumentationnear-fieldphotoplethysmographysignal quality indexsource–detector distance

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Area of Science:

  • Biomedical Engineering
  • Optical Sensing
  • Physiological Monitoring

Background:

  • Photoplethysmography (PPG) is a non-invasive optical technique for physiological monitoring.
  • Signal quality and shape are influenced by instrumentation and environmental factors.
  • The DC component of the PPG signal is crucial for certain physiological parameter calculations.

Purpose of the Study:

  • To analyze the variability of the PPG signal's DC component.
  • To investigate the effect of source-detector distance and light wavelength on PPG signal quality.
  • To propose the coefficient of variation (CV) as a novel signal quality index (SQI).

Main Methods:

  • Characterization of a PPG system using green, red, and infrared light.
  • Acquisition of PPG signals from 14 healthy participants at three source-detector distances (6 mm, 9 mm, 12 mm).
  • Utilized four photodiodes per distance and calculated the coefficient of variation (CV) for signal analysis.

Main Results:

  • Significant DC component variability was observed at a 6 mm source-detector distance.
  • DC variability homogenized at 9 mm and 12 mm distances across different light wavelengths.
  • The study identified sensitivity to near- and far-field optical effects.

Conclusions:

  • PPG system performance is distance-dependent, with near-field effects causing significant DC variability.
  • Homogenized DC component at larger distances suggests improved signal stability.
  • Variability in the DC component can impact the accuracy of derived physiological parameters, including SpO2.