Can PPG be used for HRV analysis?

Area of Science:

• Biomedical Engineering
• Physiological Monitoring
• Wearable Technology

Background:

• Heart Rate Variability (HRV) is a key indicator of autonomic nervous system (ANS) regulation, typically requiring ECG.
• Photoplethysmography (PPG) offers a convenient, non-intrusive alternative for measuring heartbeat intervals.
• The rise of wearable devices fuels interest in assessing Pulse Rate Variability (PRV) from PPG as an HRV surrogate.

Purpose of the Study:

• To investigate the efficacy of PRV features as surrogates for HRV indexes.
• To evaluate PRV's performance across three distinct populations: healthy resting, healthy post-exercise, and cardiovascular disease (CVD) subjects.
• To identify optimal PPG waveform characteristic points for PRV analysis.

Main Methods:

• Analysis of PRV features derived from PPG signals.
• Comparison of PRV-derived HRV estimates against gold-standard HRV measurements.
• Correlation and error analysis to assess the accuracy of PRV as an HRV surrogate.
• Evaluation across healthy resting, post-exercise, and CVD cohorts.

Main Results:

• PRV demonstrated significant correlations (above 82%) with HRV for both time and frequency domain features in healthy resting subjects.
• In post-exercise and CVD subjects, PRV correlations ranged from 68% to 88%, indicating a need for cautious application, especially for frequency domain features.
• Specific characteristic points on the PPG waveform were identified as crucial for accurate PRV estimation.

Conclusions:

• PRV can serve as a reliable alternative to HRV analysis in healthy individuals, particularly for time-domain features.
• The application of PRV, especially frequency-domain features, requires careful consideration in post-exercise states and in patients with cardiovascular diseases.
• Optimizing the selection of PPG waveform points is essential for maximizing the accuracy of PRV as an HRV surrogate.