Multi-wavelength photoplethysmography method for skin arterial pulse extraction

Area of Science:

• Biomedical Optics
• Physiological Measurement
• Cardiovascular Monitoring

Background:

• Photoplethysmography (PPG) is a non-invasive optical technique to measure blood volume changes.
• Single-wavelength PPG is limited in resolving depth-specific blood pulsations, affecting blood pressure (BP) accuracy.
• Cardiovascular diseases necessitate accurate and continuous BP monitoring.

Purpose of the Study:

• To develop and validate a multi-wavelength (MW) PPG method for depth-resolved skin blood pulsation measurement.
• To improve the accuracy of blood pressure (BP) estimation using pulse transit time (PTT).
• To compare the performance of MW PPG against single-wavelength PPG for BP monitoring.

Main Methods:

• Utilizing 2-3 light sources with different wavelengths to exploit wavelength-dependent light penetration in skin.
• Employing a multi-wavelength, multi-layer light-skin interaction model to isolate arterial pulsations.
• Quasi-analytically calibrating absorption weighting factors to remove capillary pulsations from PPG signals.
• Calculating BP via pulse transit time (PTT) using extracted arterial pulsations.

Main Results:

• The MW PPG method successfully extracts depth-resolved arterial blood pulsations.
• Clinical validation on 20 subjects (10 cardiovascular disease patients, 10 healthy) demonstrated improved BP accuracy.
• Systolic blood pressure (SBP) estimation accuracy improved significantly, reducing mean absolute error from 5.7 mmHg (single-wavelength) to 2.9 mmHg (three-wavelength).

Conclusions:

• The developed MW PPG method offers enhanced accuracy for non-invasive blood pressure monitoring.
• Depth resolution of blood pulsations via MW PPG is crucial for improving BP measurement precision.
• This technique shows significant potential for clinical cardiovascular disease management and monitoring.