Quantifying the correlation between photoplethysmography and laser Doppler flowmetry microvascular low-frequency...

Area of Science:

• Biomedical Engineering
• Physiology
• Optical Techniques

Background:

• Photoplethysmography (PPG) and laser Doppler flowmetry (LDF) are optical methods for monitoring microcirculation.
• Understanding the correlation between PPG and LDF across different physiological frequencies is crucial for validating their use.

Purpose of the Study:

• To assess the correlation between PPG and LDF signals in healthy subjects.
• To investigate specific low-frequency bands related to cardiac, respiratory, myogenic, neurogenic, and endothelial activities.
• To determine if PPG can serve as a cost-effective alternative to LDF.

Main Methods:

• Simultaneous recording of PPG and LDF signals from healthy male subjects.
• Wavelet analysis to divide the low-frequency integral wavelet spectrum (IWS) into physiological bands.
• Wavelet correlation and Spearman correlation analyses to quantify signal agreement.

Main Results:

• High median wavelet correlations were observed for myogenic (0.86), neurogenic (0.91), and endothelial (0.91) bands.
• Statistically significant correlations were found for cardiac (ρ = 0.64) and endothelial (ρ = 0.62) bands.
• PPG demonstrated potential as a low-cost substitute for LDF in assessing endothelial activity.

Conclusions:

• PPG and LDF exhibit good correlation across specific physiological frequency bands in microcirculation.
• PPG shows promise as a more accessible and affordable tool for evaluating endothelial function compared to LDF.