Harmonic components of photoplethysmography and pathological patterns: A cross-sectional study

Area of Science:

• Biomedical Engineering
• Cardiovascular Physiology
• Traditional Chinese Medicine

Background:

• Arterial stiffness is a significant indicator of cardiovascular health.
• Photoplethysmography (PTG) offers a non-invasive method to assess vascular function.
• Harmonic components (HCs) of PTG signals, including total harmonic distortion (THD), harmonic power (HP), and normalized harmonic amplitude (HA), are emerging as potential markers.

Purpose of the Study:

• To investigate the aging effects on PTG's harmonic components (THD, HP, HA).
• To evaluate HCs as potential markers for arterial stiffness.
• To explore the relationship between HCs and the clinical severity of phlegm, blood stasis (BS), and food retention (FR) patterns in Traditional Chinese Medicine.

Main Methods:

• Retrospective chart review of 173 female patients.
• Analysis of PTG and second derivative of PTG measurements.
• Extraction of THD, HP, and HA up to the 12th harmonic from raw PTG data.
• Correlation analysis with age, arterial stiffness indices (b/a, d/a), and pattern questionnaires (phlegm, BS, FR).

Main Results:

• THD and HA demonstrated significant aging effects.
• HCs, specifically THD and HA, were correlated with arterial stiffness indices (b/a, d/a).
• HP and HA showed positive correlations with phlegm, BS, and FR patterns in younger and middle-aged groups, with HP also correlating with FR in the middle-aged group.
• In older adults, HP and HA exhibited varied correlations (positive or negative) with the phlegm pattern.

Conclusions:

• PTG harmonic components (HCs) exhibit aging effects and are associated with arterial stiffness.
• HCs may serve as potential biomarkers for arterial stiffness and are partially related to specific Traditional Chinese Medicine patterns (phlegm, BS, FR).
• The influence of aging must be accounted for when interpreting HCs in relation to these patterns.