Optimal filter characterization for photoplethysmography-based pulse rate and pulse power spectrum estimation

Area of Science:

• Biomedical Engineering
• Physiological Monitoring
• Signal Processing

Background:

• Photoplethysmography (PPG) is a non-invasive optical method for cardiovascular assessment, gaining traction in wearables over electrocardiography (ECG).
• Existing research shows minor discrepancies between PPG and ECG heart rate measures due to underlying physiological differences.
• Optimizing PPG signal processing is crucial for accurate heart rate estimation, especially in diverse populations.

Purpose of the Study:

• To determine the optimal bandpass filter for enhancing PPG pulse detection and improving heart rate estimation.
• To characterize the spectral content of individual PPG pulses.
• To establish a baseline for advanced PPG signal processing algorithms.

Main Methods:

• Analysis of spectral coherence and signal-to-noise ratio between isolated PPG pulses and raw PPG signals.
• Evaluation of proposed methods on a database of 27,000 PPG pulses from 42 participants (adults and children).
• Identification of optimal bandpass filter frequencies for adult and pediatric groups.

Main Results:

• The optimal bandpass filter for adults was 0.6-3.3 Hz, and for children, it was 1.0-2.7 Hz.
• Spectral analysis revealed similar PPG pulse bandwidths for adults (0.8-2.4 Hz) and children (0.9-2.7 Hz).
• The study provides specific filter parameters for enhanced PPG signal processing.

Conclusions:

• The identified optimal filters significantly enhance PPG pulse detection for more accurate heart rate estimation.
• Characterizing PPG spectral content aids in understanding signal variations across age groups.
• These findings serve as a foundation for developing more sophisticated PPG-based cardiovascular monitoring tools.