An optimal filter for short photoplethysmogram signals

Area of Science:

• Biomedical Engineering
• Cardiovascular Physiology
• Signal Processing

Background:

• Photoplethysmogram (PPG) signals from wearable devices offer vital cardiovascular health insights.
• Noise interference in diverse environments challenges effective PPG signal processing.
• Enhancing PPG signal quality is crucial for accurate disease detection and health monitoring.

Purpose of the Study:

• To identify the optimal filter type and order for PPG signal processing.
• To enhance the salience of systolic and diastolic waves in filtered PPG signals.
• To utilize the skewness quality index for evaluating filter performance.

Main Methods:

• Nine filter types were evaluated across 10 different orders.
• 219 short PPG signals (2.1s) were filtered and analyzed.
• PPG signals were categorized by experts into excellent, acceptable, or unfit noise levels.

Main Results:

• The Chebyshev II filter demonstrated superior performance in improving PPG signal quality compared to other filters.
• The 4th order was identified as the optimal filter order for the Chebyshev II filter.
• The chosen filter and order effectively enhanced the visibility of key waveform features.

Conclusions:

• The Chebyshev II filter at the 4th order is recommended for processing noisy PPG signals.
• This approach improves the reliability of cardiovascular health assessments using wearable PPG technology.
• Optimized filtering enhances the diagnostic value of PPG signals for cardiovascular conditions.