Non-Invasive Blood Density Measurement using Photoplethysmography Technique
DOI:
https://doi.org/10.56294/dm2025819Keywords:
blood density, photoplethysmography, Beer–Lambert law, non-invasive biomedical deviceAbstract
Introduction:
Blood density measurement is a key diagnostic indicator for assessing hematological and cardiovascular conditions. Conventional methods require blood extraction and laboratory equipment. In this context, a non-invasive biomedical device based on photoplethysmography (PPG) and the Beer–Lambert law was developed to estimate blood density through optical parameters.
Methods:
A prototype was designed using a microcontroller, an optical sensor, and an OLED display. The acquired signals were digitally filtered through FIR and IIR algorithms to separate pulsatile and non-pulsatile components. Twenty-one volunteers were recruited, and sixteen valid recordings remained after artifact removal. Laboratory reference values were compared using linear regression and Bland–Altman analysis to evaluate concordance between clinical and device-derived measurements.
Results:
The device achieved an average error of 2.0 % for blood-density estimation, 6.06 % for hematocrit, and 7.01 % for erythrocyte count. The limits of agreement remained within clinically acceptable ranges, with a slight underestimation bias at higher density values. Main limitations were related to the restricted spectral range of the red and infrared LEDs and to physiological variables such as peripheral perfusion and involuntary movements.
Conclusions:
The proposed system demonstrated accuracy and stability for non-invasive blood-density estimation, validating PPG as a portable, low-cost diagnostic tool. Future improvements should include a broader calibration dataset and multispectral light sources with higher sensitivity to enhance linearity and dynamic range.
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Copyright (c) 2025 Theo Marcelo Galindo Chicaiza, Luz María Tobar Subía Contento , Brizeida Nohemí Gámez Aparicio , Marco Antonio Ciaccia Sortino, Cosme Damián Mejía Echeverría , Diego Luis Ortiz Morales (Author)
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